/*
 * drivers/net/wan/dscc4/dscc4.c: a DSCC4 HDLC driver for Linux
 *
 * This software may be used and distributed according to the terms of the
 * GNU General Public License.
 *
 * The author may be reached as romieu@cogenit.fr.
 * Specific bug reports/asian food will be welcome.
 *
 * Special thanks to the nice people at CS-Telecom for the hardware and the
 * access to the test/measure tools.
 *
 *
 *                             Theory of Operation
 *
 * I. Board Compatibility
 *
 * This device driver is designed for the Siemens PEB20534 4 ports serial
 * controller as found on Etinc PCISYNC cards. The documentation for the
 * chipset is available at http://www.infineon.com:
 * - Data Sheet "DSCC4, DMA Supported Serial Communication Controller with
 * 4 Channels, PEB 20534 Version 2.1, PEF 20534 Version 2.1";
 * - Application Hint "Management of DSCC4 on-chip FIFO resources".
 * - Errata sheet DS5 (courtesy of Michael Skerritt).
 * Jens David has built an adapter based on the same chipset. Take a look
 * at http://www.afthd.tu-darmstadt.de/~dg1kjd/pciscc4 for a specific
 * driver.
 * Sample code (2 revisions) is available at Infineon.
 *
 * II. Board-specific settings
 *
 * Pcisync can transmit some clock signal to the outside world on the
 * *first two* ports provided you put a quartz and a line driver on it and
 * remove the jumpers. The operation is described on Etinc web site. If you
 * go DCE on these ports, don't forget to use an adequate cable.
 *
 * Sharing of the PCI interrupt line for this board is possible.
 *
 * III. Driver operation
 *
 * The rx/tx operations are based on a linked list of descriptors. The driver
 * doesn't use HOLD mode any more. HOLD mode is definitely buggy and the more
 * I tried to fix it, the more it started to look like (convoluted) software
 * mutation of LxDA method. Errata sheet DS5 suggests to use LxDA: consider
 * this a rfc2119 MUST.
 *
 * Tx direction
 * When the tx ring is full, the xmit routine issues a call to netdev_stop.
 * The device is supposed to be enabled again during an ALLS irq (we could
 * use HI but as it's easy to lose events, it's fscked).
 *
 * Rx direction
 * The received frames aren't supposed to span over multiple receiving areas.
 * I may implement it some day but it isn't the highest ranked item.
 *
 * IV. Notes
 * The current error (XDU, RFO) recovery code is untested.
 * So far, RDO takes his RX channel down and the right sequence to enable it
 * again is still a mystery. If RDO happens, plan a reboot. More details
 * in the code (NB: as this happens, TX still works).
 * Don't mess the cables during operation, especially on DTE ports. I don't
 * suggest it for DCE either but at least one can get some messages instead
 * of a complete instant freeze.
 * Tests are done on Rev. 20 of the silicium. The RDO handling changes with
 * the documentation/chipset releases.
 *
 * TODO:
 * - test X25.
 * - use polling at high irq/s,
 * - performance analysis,
 * - endianness.
 *
 * 2001/12/10   Daniela Squassoni  <daniela@cyclades.com>
 * - Contribution to support the new generic HDLC layer.
 *
 * 2002/01      Ueimor
 * - old style interface removal
 * - dscc4_release_ring fix (related to DMA mapping)
 * - hard_start_xmit fix (hint: TxSizeMax)
 * - misc crapectomy.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/list.h>
#include <linux/ioport.h>
#include <linux/pci.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/slab.h>

#include <asm/cache.h>
#include <asm/byteorder.h>
#include <linux/uaccess.h>
#include <asm/io.h>
#include <asm/irq.h>

#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/string.h>

#include <linux/if_arp.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/delay.h>
#include <linux/hdlc.h>
#include <linux/mutex.h>

/* Version */
static const char version[] = "$Id: dscc4.c,v 1.173 2003/09/20 23:55:34 romieu Exp $ for Linux\n";
static int debug;
static int quartz;

#ifdef CONFIG_DSCC4_PCI_RST
static DEFINE_MUTEX(dscc4_mutex);
static u32 dscc4_pci_config_store[16];
#endif

#define DRV_NAME        "dscc4"

#undef DSCC4_POLLING

/* Module parameters */

MODULE_AUTHOR("Maintainer: Francois Romieu <romieu@cogenit.fr>");
MODULE_DESCRIPTION("Siemens PEB20534 PCI Controller");
MODULE_LICENSE("GPL");
module_param(debug, int, 0);
MODULE_PARM_DESC(debug,"Enable/disable extra messages");
module_param(quartz, int, 0);
MODULE_PARM_DESC(quartz,"If present, on-board quartz frequency (Hz)");

/* Structures */

struct thingie {
        int define;
        u32 bits;
};

struct TxFD {
        __le32 state;
        __le32 next;
        __le32 data;
        __le32 complete;
        u32 jiffies; /* Allows sizeof(TxFD) == sizeof(RxFD) + extra hack */
                     /* FWIW, datasheet calls that "dummy" and says that card
                      * never looks at it; neither does the driver */
};

struct RxFD {
        __le32 state1;
        __le32 next;
        __le32 data;
        __le32 state2;
        __le32 end;
};

#define DUMMY_SKB_SIZE          64
#define TX_LOW                  8
#define TX_RING_SIZE            32
#define RX_RING_SIZE            32
#define TX_TOTAL_SIZE           TX_RING_SIZE*sizeof(struct TxFD)
#define RX_TOTAL_SIZE           RX_RING_SIZE*sizeof(struct RxFD)
#define IRQ_RING_SIZE           64              /* Keep it a multiple of 32 */
#define TX_TIMEOUT              (HZ/10)
#define DSCC4_HZ_MAX            33000000
#define BRR_DIVIDER_MAX         64*0x00004000   /* Cf errata DS5 p.10 */
#define dev_per_card            4
#define SCC_REGISTERS_MAX       23              /* Cf errata DS5 p.4 */

#define SOURCE_ID(flags)        (((flags) >> 28) & 0x03)
#define TO_SIZE(state)          (((state) >> 16) & 0x1fff)

/*
 * Given the operating range of Linux HDLC, the 2 defines below could be
 * made simpler. However they are a fine reminder for the limitations of
 * the driver: it's better to stay < TxSizeMax and < RxSizeMax.
 */
#define TO_STATE_TX(len)        cpu_to_le32(((len) & TxSizeMax) << 16)
#define TO_STATE_RX(len)        cpu_to_le32((RX_MAX(len) % RxSizeMax) << 16)
#define RX_MAX(len)             ((((len) >> 5) + 1) << 5)       /* Cf RLCR */
#define SCC_REG_START(dpriv)    (SCC_START+(dpriv->dev_id)*SCC_OFFSET)

struct dscc4_pci_priv {
        __le32 *iqcfg;
        int cfg_cur;
        spinlock_t lock;
        struct pci_dev *pdev;

        struct dscc4_dev_priv *root;
        dma_addr_t iqcfg_dma;
        u32 xtal_hz;
};

struct dscc4_dev_priv {
        struct sk_buff *rx_skbuff[RX_RING_SIZE];
        struct sk_buff *tx_skbuff[TX_RING_SIZE];

        struct RxFD *rx_fd;
        struct TxFD *tx_fd;
        __le32 *iqrx;
        __le32 *iqtx;

        /* FIXME: check all the volatile are required */
        volatile u32 tx_current;
        u32 rx_current;
        u32 iqtx_current;
        u32 iqrx_current;

        volatile u32 tx_dirty;
        volatile u32 ltda;
        u32 rx_dirty;
        u32 lrda;

        dma_addr_t tx_fd_dma;
        dma_addr_t rx_fd_dma;
        dma_addr_t iqtx_dma;
        dma_addr_t iqrx_dma;

        u32 scc_regs[SCC_REGISTERS_MAX]; /* Cf errata DS5 p.4 */

        struct dscc4_pci_priv *pci_priv;
        spinlock_t lock;

        int dev_id;
        volatile u32 flags;
        u32 timer_help;

        unsigned short encoding;
        unsigned short parity;
        struct net_device *dev;
        sync_serial_settings settings;
        void __iomem *base_addr;
        u32 __pad __attribute__ ((aligned (4)));
};

/* GLOBAL registers definitions */
#define GCMDR   0x00
#define GSTAR   0x04
#define GMODE   0x08
#define IQLENR0 0x0C
#define IQLENR1 0x10
#define IQRX0   0x14
#define IQTX0   0x24
#define IQCFG   0x3c
#define FIFOCR1 0x44
#define FIFOCR2 0x48
#define FIFOCR3 0x4c
#define FIFOCR4 0x34
#define CH0CFG  0x50
#define CH0BRDA 0x54
#define CH0BTDA 0x58
#define CH0FRDA 0x98
#define CH0FTDA 0xb0
#define CH0LRDA 0xc8
#define CH0LTDA 0xe0

/* SCC registers definitions */
#define SCC_START       0x0100
#define SCC_OFFSET      0x80
#define CMDR    0x00
#define STAR    0x04
#define CCR0    0x08
#define CCR1    0x0c
#define CCR2    0x10
#define BRR     0x2C
#define RLCR    0x40
#define IMR     0x54
#define ISR     0x58

#define GPDIR   0x0400
#define GPDATA  0x0404
#define GPIM    0x0408

/* Bit masks */
#define EncodingMask    0x00700000
#define CrcMask         0x00000003

#define IntRxScc0       0x10000000
#define IntTxScc0       0x01000000

#define TxPollCmd       0x00000400
#define RxActivate      0x08000000
#define MTFi            0x04000000
#define Rdr             0x00400000
#define Rdt             0x00200000
#define Idr             0x00100000
#define Idt             0x00080000
#define TxSccRes        0x01000000
#define RxSccRes        0x00010000
#define TxSizeMax       0x1fff          /* Datasheet DS1 - 11.1.1.1 */
#define RxSizeMax       0x1ffc          /* Datasheet DS1 - 11.1.2.1 */

#define Ccr0ClockMask   0x0000003f
#define Ccr1LoopMask    0x00000200
#define IsrMask         0x000fffff
#define BrrExpMask      0x00000f00
#define BrrMultMask     0x0000003f
#define EncodingMask    0x00700000
#define Hold            cpu_to_le32(0x40000000)
#define SccBusy         0x10000000
#define PowerUp         0x80000000
#define Vis             0x00001000
#define FrameOk         (FrameVfr | FrameCrc)
#define FrameVfr        0x80
#define FrameRdo        0x40
#define FrameCrc        0x20
#define FrameRab        0x10
#define FrameAborted    cpu_to_le32(0x00000200)
#define FrameEnd        cpu_to_le32(0x80000000)
#define DataComplete    cpu_to_le32(0x40000000)
#define LengthCheck     0x00008000
#define SccEvt          0x02000000
#define NoAck           0x00000200
#define Action          0x00000001
#define HiDesc          cpu_to_le32(0x20000000)

/* SCC events */
#define RxEvt           0xf0000000
#define TxEvt           0x0f000000
#define Alls            0x00040000
#define Xdu             0x00010000
#define Cts             0x00004000
#define Xmr             0x00002000
#define Xpr             0x00001000
#define Rdo             0x00000080
#define Rfs             0x00000040
#define Cd              0x00000004
#define Rfo             0x00000002
#define Flex            0x00000001

/* DMA core events */
#define Cfg             0x00200000
#define Hi              0x00040000
#define Fi              0x00020000
#define Err             0x00010000
#define Arf             0x00000002
#define ArAck           0x00000001

/* State flags */
#define Ready           0x00000000
#define NeedIDR         0x00000001
#define NeedIDT         0x00000002
#define RdoSet          0x00000004
#define FakeReset       0x00000008

/* Don't mask RDO. Ever. */
#ifdef DSCC4_POLLING
#define EventsMask      0xfffeef7f
#else
#define EventsMask      0xfffa8f7a
#endif

/* Functions prototypes */
static void dscc4_rx_irq(struct dscc4_pci_priv *, struct dscc4_dev_priv *);
static void dscc4_tx_irq(struct dscc4_pci_priv *, struct dscc4_dev_priv *);
static int dscc4_found1(struct pci_dev *, void __iomem *ioaddr);
static int dscc4_init_one(struct pci_dev *, const struct pci_device_id *ent);
static int dscc4_open(struct net_device *);
static netdev_tx_t dscc4_start_xmit(struct sk_buff *,
                                          struct net_device *);
static int dscc4_close(struct net_device *);
static int dscc4_ioctl(struct net_device *dev, struct ifreq *rq, int cmd);
static int dscc4_init_ring(struct net_device *);
static void dscc4_release_ring(struct dscc4_dev_priv *);
static void dscc4_tx_timeout(struct net_device *);
static irqreturn_t dscc4_irq(int irq, void *dev_id);
static int dscc4_hdlc_attach(struct net_device *, unsigned short, unsigned short);
static int dscc4_set_iface(struct dscc4_dev_priv *, struct net_device *);
#ifdef DSCC4_POLLING
static int dscc4_tx_poll(struct dscc4_dev_priv *, struct net_device *);
#endif

static inline struct dscc4_dev_priv *dscc4_priv(struct net_device *dev)
{
        return dev_to_hdlc(dev)->priv;
}

static inline struct net_device *dscc4_to_dev(struct dscc4_dev_priv *p)
{
        return p->dev;
}

static void scc_patchl(u32 mask, u32 value, struct dscc4_dev_priv *dpriv,
                        struct net_device *dev, int offset)
{
        u32 state;

        /* Cf scc_writel for concern regarding thread-safety */
        state = dpriv->scc_regs[offset >> 2];
        state &= ~mask;
        state |= value;
        dpriv->scc_regs[offset >> 2] = state;
        writel(state, dpriv->base_addr + SCC_REG_START(dpriv) + offset);
}

static void scc_writel(u32 bits, struct dscc4_dev_priv *dpriv,
                       struct net_device *dev, int offset)
{
        /*
         * Thread-UNsafe.
         * As of 2002/02/16, there are no thread racing for access.
         */
        dpriv->scc_regs[offset >> 2] = bits;
        writel(bits, dpriv->base_addr + SCC_REG_START(dpriv) + offset);
}

static inline u32 scc_readl(struct dscc4_dev_priv *dpriv, int offset)
{
        return dpriv->scc_regs[offset >> 2];
}

static u32 scc_readl_star(struct dscc4_dev_priv *dpriv, struct net_device *dev)
{
        /* Cf errata DS5 p.4 */
        readl(dpriv->base_addr + SCC_REG_START(dpriv) + STAR);
        return readl(dpriv->base_addr + SCC_REG_START(dpriv) + STAR);
}

static inline void dscc4_do_tx(struct dscc4_dev_priv *dpriv,
                               struct net_device *dev)
{
        dpriv->ltda = dpriv->tx_fd_dma +
                      ((dpriv->tx_current-1)%TX_RING_SIZE)*sizeof(struct TxFD);
        writel(dpriv->ltda, dpriv->base_addr + CH0LTDA + dpriv->dev_id*4);
        /* Flush posted writes *NOW* */
        readl(dpriv->base_addr + CH0LTDA + dpriv->dev_id*4);
}

static inline void dscc4_rx_update(struct dscc4_dev_priv *dpriv,
                                   struct net_device *dev)
{
        dpriv->lrda = dpriv->rx_fd_dma +
                      ((dpriv->rx_dirty - 1)%RX_RING_SIZE)*sizeof(struct RxFD);
        writel(dpriv->lrda, dpriv->base_addr + CH0LRDA + dpriv->dev_id*4);
}

static inline unsigned int dscc4_tx_done(struct dscc4_dev_priv *dpriv)
{
        return dpriv->tx_current == dpriv->tx_dirty;
}

static inline unsigned int dscc4_tx_quiescent(struct dscc4_dev_priv *dpriv,
                                              struct net_device *dev)
{
        return readl(dpriv->base_addr + CH0FTDA + dpriv->dev_id*4) == dpriv->ltda;
}

static int state_check(u32 state, struct dscc4_dev_priv *dpriv,
                       struct net_device *dev, const char *msg)
{
        int ret = 0;

        if (debug > 1) {
                if (SOURCE_ID(state) != dpriv->dev_id) {
                        printk(KERN_DEBUG "%s (%s): Source Id=%d, state=%08x\n",
                               dev->name, msg, SOURCE_ID(state), state);
                        ret = -1;
                }
                if (state & 0x0df80c00) {
                        printk(KERN_DEBUG "%s (%s): state=%08x (UFO alert)\n",
                               dev->name, msg, state);
                        ret = -1;
                }
        }
        return ret;
}

static void dscc4_tx_print(struct net_device *dev,
                           struct dscc4_dev_priv *dpriv,
                           char *msg)
{
        printk(KERN_DEBUG "%s: tx_current=%02d tx_dirty=%02d (%s)\n",
               dev->name, dpriv->tx_current, dpriv->tx_dirty, msg);
}

static void dscc4_release_ring(struct dscc4_dev_priv *dpriv)
{
        struct device *d = &dpriv->pci_priv->pdev->dev;
        struct TxFD *tx_fd = dpriv->tx_fd;
        struct RxFD *rx_fd = dpriv->rx_fd;
        struct sk_buff **skbuff;
        int i;

        dma_free_coherent(d, TX_TOTAL_SIZE, tx_fd, dpriv->tx_fd_dma);
        dma_free_coherent(d, RX_TOTAL_SIZE, rx_fd, dpriv->rx_fd_dma);

        skbuff = dpriv->tx_skbuff;
        for (i = 0; i < TX_RING_SIZE; i++) {
                if (*skbuff) {
                        dma_unmap_single(d, le32_to_cpu(tx_fd->data),
                                         (*skbuff)->len, DMA_TO_DEVICE);
                        dev_kfree_skb(*skbuff);
                }
                skbuff++;
                tx_fd++;
        }

        skbuff = dpriv->rx_skbuff;
        for (i = 0; i < RX_RING_SIZE; i++) {
                if (*skbuff) {
                        dma_unmap_single(d, le32_to_cpu(rx_fd->data),
                                         RX_MAX(HDLC_MAX_MRU),
                                         DMA_FROM_DEVICE);
                        dev_kfree_skb(*skbuff);
                }
                skbuff++;
                rx_fd++;
        }
}

static inline int try_get_rx_skb(struct dscc4_dev_priv *dpriv,
                                 struct net_device *dev)
{
        unsigned int dirty = dpriv->rx_dirty%RX_RING_SIZE;
        struct device *d = &dpriv->pci_priv->pdev->dev;
        struct RxFD *rx_fd = dpriv->rx_fd + dirty;
        const int len = RX_MAX(HDLC_MAX_MRU);
        struct sk_buff *skb;
        dma_addr_t addr;

        skb = dev_alloc_skb(len);
        if (!skb)
                goto err_out;

        skb->protocol = hdlc_type_trans(skb, dev);
        addr = dma_map_single(d, skb->data, len, DMA_FROM_DEVICE);
        if (dma_mapping_error(d, addr))
                goto err_free_skb;

        dpriv->rx_skbuff[dirty] = skb;
        rx_fd->data = cpu_to_le32(addr);
        return 0;

err_free_skb:
        dev_kfree_skb_any(skb);
err_out:
        rx_fd->data = 0;
        return -1;
}

/*
 * IRQ/thread/whatever safe
 */
static int dscc4_wait_ack_cec(struct dscc4_dev_priv *dpriv,
                              struct net_device *dev, char *msg)
{
        s8 i = 0;

        do {
                if (!(scc_readl_star(dpriv, dev) & SccBusy)) {
                        printk(KERN_DEBUG "%s: %s ack (%d try)\n", dev->name,
                               msg, i);
                        goto done;
                }
                schedule_timeout_uninterruptible(msecs_to_jiffies(100));
                rmb();
        } while (++i > 0);
        netdev_err(dev, "%s timeout\n", msg);
done:
        return (i >= 0) ? i : -EAGAIN;
}

static int dscc4_do_action(struct net_device *dev, char *msg)
{
        void __iomem *ioaddr = dscc4_priv(dev)->base_addr;
        s16 i = 0;

        writel(Action, ioaddr + GCMDR);
        ioaddr += GSTAR;
        do {
                u32 state = readl(ioaddr);

                if (state & ArAck) {
                        netdev_dbg(dev, "%s ack\n", msg);
                        writel(ArAck, ioaddr);
                        goto done;
                } else if (state & Arf) {
                        netdev_err(dev, "%s failed\n", msg);
                        writel(Arf, ioaddr);
                        i = -1;
                        goto done;
        }
                rmb();
        } while (++i > 0);
        netdev_err(dev, "%s timeout\n", msg);
done:
        return i;
}

static inline int dscc4_xpr_ack(struct dscc4_dev_priv *dpriv)
{
        int cur = dpriv->iqtx_current%IRQ_RING_SIZE;
        s8 i = 0;

        do {
                if (!(dpriv->flags & (NeedIDR | NeedIDT)) ||
                    (dpriv->iqtx[cur] & cpu_to_le32(Xpr)))
                        break;
                smp_rmb();
                schedule_timeout_uninterruptible(msecs_to_jiffies(100));
        } while (++i > 0);

        return (i >= 0 ) ? i : -EAGAIN;
}

#if 0 /* dscc4_{rx/tx}_reset are both unreliable - more tweak needed */
static void dscc4_rx_reset(struct dscc4_dev_priv *dpriv, struct net_device *dev)
{
        unsigned long flags;

        spin_lock_irqsave(&dpriv->pci_priv->lock, flags);
        /* Cf errata DS5 p.6 */
        writel(0x00000000, dpriv->base_addr + CH0LRDA + dpriv->dev_id*4);
        scc_patchl(PowerUp, 0, dpriv, dev, CCR0);
        readl(dpriv->base_addr + CH0LRDA + dpriv->dev_id*4);
        writel(MTFi|Rdr, dpriv->base_addr + dpriv->dev_id*0x0c + CH0CFG);
        writel(Action, dpriv->base_addr + GCMDR);
        spin_unlock_irqrestore(&dpriv->pci_priv->lock, flags);
}

#endif

#if 0
static void dscc4_tx_reset(struct dscc4_dev_priv *dpriv, struct net_device *dev)
{
        u16 i = 0;

        /* Cf errata DS5 p.7 */
        scc_patchl(PowerUp, 0, dpriv, dev, CCR0);
        scc_writel(0x00050000, dpriv, dev, CCR2);
        /*
         * Must be longer than the time required to fill the fifo.
         */
        while (!dscc4_tx_quiescent(dpriv, dev) && ++i) {
                udelay(1);
                wmb();
        }

        writel(MTFi|Rdt, dpriv->base_addr + dpriv->dev_id*0x0c + CH0CFG);
        if (dscc4_do_action(dev, "Rdt") < 0)
                netdev_err(dev, "Tx reset failed\n");
}
#endif

/* TODO: (ab)use this function to refill a completely depleted RX ring. */
static inline void dscc4_rx_skb(struct dscc4_dev_priv *dpriv,
                                struct net_device *dev)
{
        struct RxFD *rx_fd = dpriv->rx_fd + dpriv->rx_current%RX_RING_SIZE;
        struct device *d = &dpriv->pci_priv->pdev->dev;
        struct sk_buff *skb;
        int pkt_len;

        skb = dpriv->rx_skbuff[dpriv->rx_current++%RX_RING_SIZE];
        if (!skb) {
                printk(KERN_DEBUG "%s: skb=0 (%s)\n", dev->name, __func__);
                goto refill;
        }
        pkt_len = TO_SIZE(le32_to_cpu(rx_fd->state2));
        dma_unmap_single(d, le32_to_cpu(rx_fd->data),
                         RX_MAX(HDLC_MAX_MRU), DMA_FROM_DEVICE);
        if ((skb->data[--pkt_len] & FrameOk) == FrameOk) {
                dev->stats.rx_packets++;
                dev->stats.rx_bytes += pkt_len;
                skb_put(skb, pkt_len);
                if (netif_running(dev))
                        skb->protocol = hdlc_type_trans(skb, dev);
                netif_rx(skb);
        } else {
                if (skb->data[pkt_len] & FrameRdo)
                        dev->stats.rx_fifo_errors++;
                else if (!(skb->data[pkt_len] & FrameCrc))
                        dev->stats.rx_crc_errors++;
                else if ((skb->data[pkt_len] & (FrameVfr | FrameRab)) !=
                         (FrameVfr | FrameRab))
                        dev->stats.rx_length_errors++;
                dev->stats.rx_errors++;
                dev_kfree_skb_irq(skb);
        }
refill:
        while ((dpriv->rx_dirty - dpriv->rx_current) % RX_RING_SIZE) {
                if (try_get_rx_skb(dpriv, dev) < 0)
                        break;
                dpriv->rx_dirty++;
        }
        dscc4_rx_update(dpriv, dev);
        rx_fd->state2 = 0x00000000;
        rx_fd->end = cpu_to_le32(0xbabeface);
}

static void dscc4_free1(struct pci_dev *pdev)
{
        struct dscc4_pci_priv *ppriv;
        struct dscc4_dev_priv *root;
        int i;

        ppriv = pci_get_drvdata(pdev);
        root = ppriv->root;

        for (i = 0; i < dev_per_card; i++)
                unregister_hdlc_device(dscc4_to_dev(root + i));

        for (i = 0; i < dev_per_card; i++)
                free_netdev(root[i].dev);
        kfree(root);
        kfree(ppriv);
}

static int dscc4_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
{
        struct dscc4_pci_priv *priv;
        struct dscc4_dev_priv *dpriv;
        void __iomem *ioaddr;
        int i, rc;

        printk(KERN_DEBUG "%s", version);

        rc = pci_enable_device(pdev);
        if (rc < 0)
                goto out;

        rc = pci_request_region(pdev, 0, "registers");
        if (rc < 0) {
                pr_err("can't reserve MMIO region (regs)\n");
                goto err_disable_0;
        }
        rc = pci_request_region(pdev, 1, "LBI interface");
        if (rc < 0) {
                pr_err("can't reserve MMIO region (lbi)\n");
                goto err_free_mmio_region_1;
        }

        ioaddr = pci_ioremap_bar(pdev, 0);
        if (!ioaddr) {
                pr_err("cannot remap MMIO region %llx @ %llx\n",
                       (unsigned long long)pci_resource_len(pdev, 0),
                       (unsigned long long)pci_resource_start(pdev, 0));
                rc = -EIO;
                goto err_free_mmio_regions_2;
        }
        printk(KERN_DEBUG "Siemens DSCC4, MMIO at %#llx (regs), %#llx (lbi), IRQ %d\n",
                (unsigned long long)pci_resource_start(pdev, 0),
                (unsigned long long)pci_resource_start(pdev, 1), pdev->irq);

        /* Cf errata DS5 p.2 */
        pci_write_config_byte(pdev, PCI_LATENCY_TIMER, 0xf8);
        pci_set_master(pdev);

        rc = dscc4_found1(pdev, ioaddr);
        if (rc < 0)
                goto err_iounmap_3;

        priv = pci_get_drvdata(pdev);

        rc = request_irq(pdev->irq, dscc4_irq, IRQF_SHARED, DRV_NAME, priv->root);
        if (rc < 0) {
                pr_warn("IRQ %d busy\n", pdev->irq);
                goto err_release_4;
        }

        /* power up/little endian/dma core controlled via lrda/ltda */
        writel(0x00000001, ioaddr + GMODE);
        /* Shared interrupt queue */
        {
                u32 bits;

                bits = (IRQ_RING_SIZE >> 5) - 1;
                bits |= bits << 4;
                bits |= bits << 8;
                bits |= bits << 16;
                writel(bits, ioaddr + IQLENR0);
        }
        /* Global interrupt queue */
        writel((u32)(((IRQ_RING_SIZE >> 5) - 1) << 20), ioaddr + IQLENR1);

        rc = -ENOMEM;

        priv->iqcfg = (__le32 *)dma_alloc_coherent(&pdev->dev,
                IRQ_RING_SIZE*sizeof(__le32), &priv->iqcfg_dma, GFP_KERNEL);
        if (!priv->iqcfg)
                goto err_free_irq_5;
        writel(priv->iqcfg_dma, ioaddr + IQCFG);

        /*
         * SCC 0-3 private rx/tx irq structures
         * IQRX/TXi needs to be set soon. Learned it the hard way...
         */
        for (i = 0; i < dev_per_card; i++) {
                dpriv = priv->root + i;
                dpriv->iqtx = (__le32 *)dma_alloc_coherent(&pdev->dev,
                        IRQ_RING_SIZE*sizeof(u32), &dpriv->iqtx_dma,
                        GFP_KERNEL);
                if (!dpriv->iqtx)
                        goto err_free_iqtx_6;
                writel(dpriv->iqtx_dma, ioaddr + IQTX0 + i*4);
        }
        for (i = 0; i < dev_per_card; i++) {
                dpriv = priv->root + i;
                dpriv->iqrx = (__le32 *)dma_alloc_coherent(&pdev->dev,
                        IRQ_RING_SIZE*sizeof(u32), &dpriv->iqrx_dma,
                        GFP_KERNEL);
                if (!dpriv->iqrx)
                        goto err_free_iqrx_7;
                writel(dpriv->iqrx_dma, ioaddr + IQRX0 + i*4);
        }

        /* Cf application hint. Beware of hard-lock condition on threshold. */
        writel(0x42104000, ioaddr + FIFOCR1);
        //writel(0x9ce69800, ioaddr + FIFOCR2);
        writel(0xdef6d800, ioaddr + FIFOCR2);
        //writel(0x11111111, ioaddr + FIFOCR4);
        writel(0x18181818, ioaddr + FIFOCR4);
        // FIXME: should depend on the chipset revision
        writel(0x0000000e, ioaddr + FIFOCR3);

        writel(0xff200001, ioaddr + GCMDR);

        rc = 0;
out:
        return rc;

err_free_iqrx_7:
        while (--i >= 0) {
                dpriv = priv->root + i;
                dma_free_coherent(&pdev->dev, IRQ_RING_SIZE*sizeof(u32),
                                  dpriv->iqrx, dpriv->iqrx_dma);
        }
        i = dev_per_card;
err_free_iqtx_6:
        while (--i >= 0) {
                dpriv = priv->root + i;
                dma_free_coherent(&pdev->dev, IRQ_RING_SIZE*sizeof(u32),
                                  dpriv->iqtx, dpriv->iqtx_dma);
        }
        dma_free_coherent(&pdev->dev, IRQ_RING_SIZE*sizeof(u32), priv->iqcfg,
                          priv->iqcfg_dma);
err_free_irq_5:
        free_irq(pdev->irq, priv->root);
err_release_4:
        dscc4_free1(pdev);
err_iounmap_3:
        iounmap (ioaddr);
err_free_mmio_regions_2:
        pci_release_region(pdev, 1);
err_free_mmio_region_1:
        pci_release_region(pdev, 0);
err_disable_0:
        pci_disable_device(pdev);
        goto out;
};

/*
 * Let's hope the default values are decent enough to protect my
 * feet from the user's gun - Ueimor
 */
static void dscc4_init_registers(struct dscc4_dev_priv *dpriv,
                                 struct net_device *dev)
{
        /* No interrupts, SCC core disabled. Let's relax */
        scc_writel(0x00000000, dpriv, dev, CCR0);

        scc_writel(LengthCheck | (HDLC_MAX_MRU >> 5), dpriv, dev, RLCR);

        /*
         * No address recognition/crc-CCITT/cts enabled
         * Shared flags transmission disabled - cf errata DS5 p.11
         * Carrier detect disabled - cf errata p.14
         * FIXME: carrier detection/polarity may be handled more gracefully.
         */
        scc_writel(0x02408000, dpriv, dev, CCR1);

        /* crc not forwarded - Cf errata DS5 p.11 */
        scc_writel(0x00050008 & ~RxActivate, dpriv, dev, CCR2);
        // crc forwarded
        //scc_writel(0x00250008 & ~RxActivate, dpriv, dev, CCR2);
}

static inline int dscc4_set_quartz(struct dscc4_dev_priv *dpriv, int hz)
{
        int ret = 0;

        if ((hz < 0) || (hz > DSCC4_HZ_MAX))
                ret = -EOPNOTSUPP;
        else
                dpriv->pci_priv->xtal_hz = hz;

        return ret;
}

static const struct net_device_ops dscc4_ops = {
        .ndo_open       = dscc4_open,
        .ndo_stop       = dscc4_close,
        .ndo_start_xmit = hdlc_start_xmit,
        .ndo_do_ioctl   = dscc4_ioctl,
        .ndo_tx_timeout = dscc4_tx_timeout,
};

static int dscc4_found1(struct pci_dev *pdev, void __iomem *ioaddr)
{
        struct dscc4_pci_priv *ppriv;
        struct dscc4_dev_priv *root;
        int i, ret = -ENOMEM;

        root = kcalloc(dev_per_card, sizeof(*root), GFP_KERNEL);
        if (!root)
                goto err_out;

        for (i = 0; i < dev_per_card; i++) {
                root[i].dev = alloc_hdlcdev(root + i);
                if (!root[i].dev)
                        goto err_free_dev;
        }

        ppriv = kzalloc(sizeof(*ppriv), GFP_KERNEL);
        if (!ppriv)
                goto err_free_dev;

        ppriv->root = root;
        spin_lock_init(&ppriv->lock);

        for (i = 0; i < dev_per_card; i++) {
                struct dscc4_dev_priv *dpriv = root + i;
                struct net_device *d = dscc4_to_dev(dpriv);
                hdlc_device *hdlc = dev_to_hdlc(d);

                d->base_addr = (unsigned long)ioaddr;
                d->irq = pdev->irq;
                d->netdev_ops = &dscc4_ops;
                d->watchdog_timeo = TX_TIMEOUT;
                SET_NETDEV_DEV(d, &pdev->dev);

                dpriv->dev_id = i;
                dpriv->pci_priv = ppriv;
                dpriv->base_addr = ioaddr;
                spin_lock_init(&dpriv->lock);

                hdlc->xmit = dscc4_start_xmit;
                hdlc->attach = dscc4_hdlc_attach;

                dscc4_init_registers(dpriv, d);
                dpriv->parity = PARITY_CRC16_PR0_CCITT;
                dpriv->encoding = ENCODING_NRZ;
        
                ret = dscc4_init_ring(d);
                if (ret < 0)
                        goto err_unregister;

                ret = register_hdlc_device(d);
                if (ret < 0) {
                        pr_err("unable to register\n");
                        dscc4_release_ring(dpriv);
                        goto err_unregister;
                }
        }

        ret = dscc4_set_quartz(root, quartz);
        if (ret < 0)
                goto err_unregister;

        pci_set_drvdata(pdev, ppriv);
        return ret;

err_unregister:
        while (i-- > 0) {
                dscc4_release_ring(root + i);
                unregister_hdlc_device(dscc4_to_dev(root + i));
        }
        kfree(ppriv);
        i = dev_per_card;
err_free_dev:
        while (i-- > 0)
                free_netdev(root[i].dev);
        kfree(root);
err_out:
        return ret;
};

static void dscc4_tx_timeout(struct net_device *dev)
{
        /* FIXME: something is missing there */
}

static int dscc4_loopback_check(struct dscc4_dev_priv *dpriv)
{
        sync_serial_settings *settings = &dpriv->settings;

        if (settings->loopback && (settings->clock_type != CLOCK_INT)) {
                struct net_device *dev = dscc4_to_dev(dpriv);

                netdev_info(dev, "loopback requires clock\n");
                return -1;
        }
        return 0;
}

#ifdef CONFIG_DSCC4_PCI_RST
/*
 * Some DSCC4-based cards wires the GPIO port and the PCI #RST pin together
 * so as to provide a safe way to reset the asic while not the whole machine
 * rebooting.
 *
 * This code doesn't need to be efficient. Keep It Simple
 */
static void dscc4_pci_reset(struct pci_dev *pdev, void __iomem *ioaddr)
{
        int i;

        mutex_lock(&dscc4_mutex);
        for (i = 0; i < 16; i++)
                pci_read_config_dword(pdev, i << 2, dscc4_pci_config_store + i);

        /* Maximal LBI clock divider (who cares ?) and whole GPIO range. */
        writel(0x001c0000, ioaddr + GMODE);
        /* Configure GPIO port as output */
        writel(0x0000ffff, ioaddr + GPDIR);
        /* Disable interruption */
        writel(0x0000ffff, ioaddr + GPIM);

        writel(0x0000ffff, ioaddr + GPDATA);
        writel(0x00000000, ioaddr + GPDATA);

        /* Flush posted writes */
        readl(ioaddr + GSTAR);

        schedule_timeout_uninterruptible(msecs_to_jiffies(100));

        for (i = 0; i < 16; i++)
                pci_write_config_dword(pdev, i << 2, dscc4_pci_config_store[i]);
        mutex_unlock(&dscc4_mutex);
}
#else
#define dscc4_pci_reset(pdev,ioaddr)    do {} while (0)
#endif /* CONFIG_DSCC4_PCI_RST */

static int dscc4_open(struct net_device *dev)
{
        struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
        int ret = -EAGAIN;

        if ((dscc4_loopback_check(dpriv) < 0))
                goto err;

        if ((ret = hdlc_open(dev)))
                goto err;

        /*
         * Due to various bugs, there is no way to reliably reset a
         * specific port (manufacturer's dependent special PCI #RST wiring
         * apart: it affects all ports). Thus the device goes in the best
         * silent mode possible at dscc4_close() time and simply claims to
         * be up if it's opened again. It still isn't possible to change
         * the HDLC configuration without rebooting but at least the ports
         * can be up/down ifconfig'ed without killing the host.
         */
        if (dpriv->flags & FakeReset) {
                dpriv->flags &= ~FakeReset;
                scc_patchl(0, PowerUp, dpriv, dev, CCR0);
                scc_patchl(0, 0x00050000, dpriv, dev, CCR2);
                scc_writel(EventsMask, dpriv, dev, IMR);
                netdev_info(dev, "up again\n");
                goto done;
        }

        /* IDT+IDR during XPR */
        dpriv->flags = NeedIDR | NeedIDT;

        scc_patchl(0, PowerUp | Vis, dpriv, dev, CCR0);

        /*
         * The following is a bit paranoid...
         *
         * NB: the datasheet "...CEC will stay active if the SCC is in
         * power-down mode or..." and CCR2.RAC = 1 are two different
         * situations.
         */
        if (scc_readl_star(dpriv, dev) & SccBusy) {
                netdev_err(dev, "busy - try later\n");
                ret = -EAGAIN;
                goto err_out;
        } else
                netdev_info(dev, "available - good\n");

        scc_writel(EventsMask, dpriv, dev, IMR);

        /* Posted write is flushed in the wait_ack loop */
        scc_writel(TxSccRes | RxSccRes, dpriv, dev, CMDR);

        if ((ret = dscc4_wait_ack_cec(dpriv, dev, "Cec")) < 0)
                goto err_disable_scc_events;

        /*
         * I would expect XPR near CE completion (before ? after ?).
         * At worst, this code won't see a late XPR and people
         * will have to re-issue an ifconfig (this is harmless).
         * WARNING, a really missing XPR usually means a hardware
         * reset is needed. Suggestions anyone ?
         */
        if ((ret = dscc4_xpr_ack(dpriv)) < 0) {
                pr_err("XPR timeout\n");
                goto err_disable_scc_events;
        }
        
        if (debug > 2)
                dscc4_tx_print(dev, dpriv, "Open");

done:
        netif_start_queue(dev);

        netif_carrier_on(dev);

        return 0;

err_disable_scc_events:
        scc_writel(0xffffffff, dpriv, dev, IMR);
        scc_patchl(PowerUp | Vis, 0, dpriv, dev, CCR0);
err_out:
        hdlc_close(dev);
err:
        return ret;
}

#ifdef DSCC4_POLLING
static int dscc4_tx_poll(struct dscc4_dev_priv *dpriv, struct net_device *dev)
{
        /* FIXME: it's gonna be easy (TM), for sure */
}
#endif /* DSCC4_POLLING */

static netdev_tx_t dscc4_start_xmit(struct sk_buff *skb,
                                          struct net_device *dev)
{
        struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
        struct device *d = &dpriv->pci_priv->pdev->dev;
        struct TxFD *tx_fd;
        dma_addr_t addr;
        int next;

        addr = dma_map_single(d, skb->data, skb->len, DMA_TO_DEVICE);
        if (dma_mapping_error(d, addr)) {
                dev_kfree_skb_any(skb);
                dev->stats.tx_dropped++;
                return NETDEV_TX_OK;
        }

        next = dpriv->tx_current%TX_RING_SIZE;
        dpriv->tx_skbuff[next] = skb;
        tx_fd = dpriv->tx_fd + next;
        tx_fd->state = FrameEnd | TO_STATE_TX(skb->len);
        tx_fd->data = cpu_to_le32(addr);
        tx_fd->complete = 0x00000000;
        tx_fd->jiffies = jiffies;
        mb();

#ifdef DSCC4_POLLING
        spin_lock(&dpriv->lock);
        while (dscc4_tx_poll(dpriv, dev));
        spin_unlock(&dpriv->lock);
#endif

        if (debug > 2)
                dscc4_tx_print(dev, dpriv, "Xmit");
        /* To be cleaned(unsigned int)/optimized. Later, ok ? */
        if (!((++dpriv->tx_current - dpriv->tx_dirty)%TX_RING_SIZE))
                netif_stop_queue(dev);

        if (dscc4_tx_quiescent(dpriv, dev))
                dscc4_do_tx(dpriv, dev);

        return NETDEV_TX_OK;
}

static int dscc4_close(struct net_device *dev)
{
        struct dscc4_dev_priv *dpriv = dscc4_priv(dev);

        netif_stop_queue(dev);

        scc_patchl(PowerUp | Vis, 0, dpriv, dev, CCR0);
        scc_patchl(0x00050000, 0, dpriv, dev, CCR2);
        scc_writel(0xffffffff, dpriv, dev, IMR);

        dpriv->flags |= FakeReset;

        hdlc_close(dev);

        return 0;
}

static inline int dscc4_check_clock_ability(int port)
{
        int ret = 0;

#ifdef CONFIG_DSCC4_PCISYNC
        if (port >= 2)
                ret = -1;
#endif
        return ret;
}

/*
 * DS1 p.137: "There are a total of 13 different clocking modes..."
 *                                  ^^
 * Design choices:
 * - by default, assume a clock is provided on pin RxClk/TxClk (clock mode 0a).
 *   Clock mode 3b _should_ work but the testing seems to make this point
 *   dubious (DIY testing requires setting CCR0 at 0x00000033).
 *   This is supposed to provide least surprise "DTE like" behavior.
 * - if line rate is specified, clocks are assumed to be locally generated.
 *   A quartz must be available (on pin XTAL1). Modes 6b/7b are used. Choosing
 *   between these it automagically done according on the required frequency
 *   scaling. Of course some rounding may take place.
 * - no high speed mode (40Mb/s). May be trivial to do but I don't have an
 *   appropriate external clocking device for testing.
 * - no time-slot/clock mode 5: shameless laziness.
 *
 * The clock signals wiring can be (is ?) manufacturer dependent. Good luck.
 *
 * BIG FAT WARNING: if the device isn't provided enough clocking signal, it
 * won't pass the init sequence. For example, straight back-to-back DTE without
 * external clock will fail when dscc4_open() (<- 'ifconfig hdlcx xxx') is
 * called.
 *
 * Typos lurk in datasheet (missing divier in clock mode 7a figure 51 p.153
 * DS0 for example)
 *
 * Clock mode related bits of CCR0:
 *     +------------ TOE: output TxClk (0b/2b/3a/3b/6b/7a/7b only)
 *     | +---------- SSEL: sub-mode select 0 -> a, 1 -> b
 *     | | +-------- High Speed: say 0
 *     | | | +-+-+-- Clock Mode: 0..7
 *     | | | | | |
 * -+-+-+-+-+-+-+-+
 * x|x|5|4|3|2|1|0| lower bits
 *
 * Division factor of BRR: k = (N+1)x2^M (total divider = 16xk in mode 6b)
 *            +-+-+-+------------------ M (0..15)
 *            | | | |     +-+-+-+-+-+-- N (0..63)
 *    0 0 0 0 | | | | 0 0 | | | | | |
 * ...-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *    f|e|d|c|b|a|9|8|7|6|5|4|3|2|1|0| lower bits
 *
 */
static int dscc4_set_clock(struct net_device *dev, u32 *bps, u32 *state)
{
        struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
        int ret = -1;
        u32 brr;

        *state &= ~Ccr0ClockMask;
        if (*bps) { /* Clock generated - required for DCE */
                u32 n = 0, m = 0, divider;
                int xtal;

                xtal = dpriv->pci_priv->xtal_hz;
                if (!xtal)
                        goto done;
                if (dscc4_check_clock_ability(dpriv->dev_id) < 0)
                        goto done;
                divider = xtal / *bps;
                if (divider > BRR_DIVIDER_MAX) {
                        divider >>= 4;
                        *state |= 0x00000036; /* Clock mode 6b (BRG/16) */
                } else
                        *state |= 0x00000037; /* Clock mode 7b (BRG) */
                if (divider >> 22) {
                        n = 63;
                        m = 15;
                } else if (divider) {
                        /* Extraction of the 6 highest weighted bits */
                        m = 0;
                        while (0xffffffc0 & divider) {
                                m++;
                                divider >>= 1;
                        }
                        n = divider;
                }
                brr = (m << 8) | n;
                divider = n << m;
                if (!(*state & 0x00000001)) /* ?b mode mask => clock mode 6b */
                        divider <<= 4;
                *bps = xtal / divider;
        } else {
                /*
                 * External clock - DTE
                 * "state" already reflects Clock mode 0a (CCR0 = 0xzzzzzz00).
                 * Nothing more to be done
                 */
                brr = 0;
        }
        scc_writel(brr, dpriv, dev, BRR);
        ret = 0;
done:
        return ret;
}

static int dscc4_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
        sync_serial_settings __user *line = ifr->ifr_settings.ifs_ifsu.sync;
        struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
        const size_t size = sizeof(dpriv->settings);
        int ret = 0;

        if (dev->flags & IFF_UP)
                return -EBUSY;

        if (cmd != SIOCWANDEV)
                return -EOPNOTSUPP;

        switch(ifr->ifr_settings.type) {
        case IF_GET_IFACE:
                ifr->ifr_settings.type = IF_IFACE_SYNC_SERIAL;
                if (ifr->ifr_settings.size < size) {
                        ifr->ifr_settings.size = size; /* data size wanted */
                        return -ENOBUFS;
                }
                if (copy_to_user(line, &dpriv->settings, size))
                        return -EFAULT;
                break;

        case IF_IFACE_SYNC_SERIAL:
                if (!capable(CAP_NET_ADMIN))
                        return -EPERM;

                if (dpriv->flags & FakeReset) {
                        netdev_info(dev, "please reset the device before this command\n");
                        return -EPERM;
                }
                if (copy_from_user(&dpriv->settings, line, size))
                        return -EFAULT;
                ret = dscc4_set_iface(dpriv, dev);
                break;

        default:
                ret = hdlc_ioctl(dev, ifr, cmd);
                break;
        }

        return ret;
}

static int dscc4_match(const struct thingie *p, int value)
{
        int i;

        for (i = 0; p[i].define != -1; i++) {
                if (value == p[i].define)
                        break;
        }
        if (p[i].define == -1)
                return -1;
        else
                return i;
}

static int dscc4_clock_setting(struct dscc4_dev_priv *dpriv,
                               struct net_device *dev)
{
        sync_serial_settings *settings = &dpriv->settings;
        int ret = -EOPNOTSUPP;
        u32 bps, state;

        bps = settings->clock_rate;
        state = scc_readl(dpriv, CCR0);
        if (dscc4_set_clock(dev, &bps, &state) < 0)
                goto done;
        if (bps) { /* DCE */
                printk(KERN_DEBUG "%s: generated RxClk (DCE)\n", dev->name);
                if (settings->clock_rate != bps) {
                        printk(KERN_DEBUG "%s: clock adjusted (%08d -> %08d)\n",
                                dev->name, settings->clock_rate, bps);
                        settings->clock_rate = bps;
                }
        } else { /* DTE */
                state |= PowerUp | Vis;
                printk(KERN_DEBUG "%s: external RxClk (DTE)\n", dev->name);
        }
        scc_writel(state, dpriv, dev, CCR0);
        ret = 0;
done:
        return ret;
}

static int dscc4_encoding_setting(struct dscc4_dev_priv *dpriv,
                                  struct net_device *dev)
{
        static const struct thingie encoding[] = {
                { ENCODING_NRZ,         0x00000000 },
                { ENCODING_NRZI,        0x00200000 },
                { ENCODING_FM_MARK,     0x00400000 },
                { ENCODING_FM_SPACE,    0x00500000 },
                { ENCODING_MANCHESTER,  0x00600000 },
                { -1,                   0}
        };
        int i, ret = 0;

        i = dscc4_match(encoding, dpriv->encoding);
        if (i >= 0)
                scc_patchl(EncodingMask, encoding[i].bits, dpriv, dev, CCR0);
        else
                ret = -EOPNOTSUPP;
        return ret;
}

static int dscc4_loopback_setting(struct dscc4_dev_priv *dpriv,
                                  struct net_device *dev)
{
        sync_serial_settings *settings = &dpriv->settings;
        u32 state;

        state = scc_readl(dpriv, CCR1);
        if (settings->loopback) {
                printk(KERN_DEBUG "%s: loopback\n", dev->name);
                state |= 0x00000100;
        } else {
                printk(KERN_DEBUG "%s: normal\n", dev->name);
                state &= ~0x00000100;
        }
        scc_writel(state, dpriv, dev, CCR1);
        return 0;
}

static int dscc4_crc_setting(struct dscc4_dev_priv *dpriv,
                             struct net_device *dev)
{
        static const struct thingie crc[] = {
                { PARITY_CRC16_PR0_CCITT,       0x00000010 },
                { PARITY_CRC16_PR1_CCITT,       0x00000000 },
                { PARITY_CRC32_PR0_CCITT,       0x00000011 },
                { PARITY_CRC32_PR1_CCITT,       0x00000001 }
        };
        int i, ret = 0;

        i = dscc4_match(crc, dpriv->parity);
        if (i >= 0)
                scc_patchl(CrcMask, crc[i].bits, dpriv, dev, CCR1);
        else
                ret = -EOPNOTSUPP;
        return ret;
}

static int dscc4_set_iface(struct dscc4_dev_priv *dpriv, struct net_device *dev)
{
        struct {
                int (*action)(struct dscc4_dev_priv *, struct net_device *);
        } *p, do_setting[] = {
                { dscc4_encoding_setting },
                { dscc4_clock_setting },
                { dscc4_loopback_setting },
                { dscc4_crc_setting },
                { NULL }
        };
        int ret = 0;

        for (p = do_setting; p->action; p++) {
                if ((ret = p->action(dpriv, dev)) < 0)
                        break;
        }
        return ret;
}

static irqreturn_t dscc4_irq(int irq, void *token)
{
        struct dscc4_dev_priv *root = token;
        struct dscc4_pci_priv *priv;
        struct net_device *dev;
        void __iomem *ioaddr;
        u32 state;
        unsigned long flags;
        int i, handled = 1;

        priv = root->pci_priv;
        dev = dscc4_to_dev(root);

        spin_lock_irqsave(&priv->lock, flags);

        ioaddr = root->base_addr;

        state = readl(ioaddr + GSTAR);
        if (!state) {
                handled = 0;
                goto out;
        }
        if (debug > 3)
                printk(KERN_DEBUG "%s: GSTAR = 0x%08x\n", DRV_NAME, state);
        writel(state, ioaddr + GSTAR);

        if (state & Arf) {
                netdev_err(dev, "failure (Arf). Harass the maintainer\n");
                goto out;
        }
        state &= ~ArAck;
        if (state & Cfg) {
                if (debug > 0)
                        printk(KERN_DEBUG "%s: CfgIV\n", DRV_NAME);
                if (priv->iqcfg[priv->cfg_cur++%IRQ_RING_SIZE] & cpu_to_le32(Arf))
                        netdev_err(dev, "CFG failed\n");
                if (!(state &= ~Cfg))
                        goto out;
        }
        if (state & RxEvt) {
                i = dev_per_card - 1;
                do {
                        dscc4_rx_irq(priv, root + i);
                } while (--i >= 0);
                state &= ~RxEvt;
        }
        if (state & TxEvt) {
                i = dev_per_card - 1;
                do {
                        dscc4_tx_irq(priv, root + i);
                } while (--i >= 0);
                state &= ~TxEvt;
        }
out:
        spin_unlock_irqrestore(&priv->lock, flags);
        return IRQ_RETVAL(handled);
}

static void dscc4_tx_irq(struct dscc4_pci_priv *ppriv,
                                struct dscc4_dev_priv *dpriv)
{
        struct net_device *dev = dscc4_to_dev(dpriv);
        u32 state;
        int cur, loop = 0;

try:
        cur = dpriv->iqtx_current%IRQ_RING_SIZE;
        state = le32_to_cpu(dpriv->iqtx[cur]);
        if (!state) {
                if (debug > 4)
                        printk(KERN_DEBUG "%s: Tx ISR = 0x%08x\n", dev->name,
                               state);
                if ((debug > 1) && (loop > 1))
                        printk(KERN_DEBUG "%s: Tx irq loop=%d\n", dev->name, loop);
                if (loop && netif_queue_stopped(dev))
                        if ((dpriv->tx_current - dpriv->tx_dirty)%TX_RING_SIZE)
                                netif_wake_queue(dev);

                if (netif_running(dev) && dscc4_tx_quiescent(dpriv, dev) &&
                    !dscc4_tx_done(dpriv))
                                dscc4_do_tx(dpriv, dev);
                return;
        }
        loop++;
        dpriv->iqtx[cur] = 0;
        dpriv->iqtx_current++;

        if (state_check(state, dpriv, dev, "Tx") < 0)
                return;

        if (state & SccEvt) {
                if (state & Alls) {
                        struct sk_buff *skb;
                        struct TxFD *tx_fd;

                        if (debug > 2)
                                dscc4_tx_print(dev, dpriv, "Alls");
                        /*
                         * DataComplete can't be trusted for Tx completion.
                         * Cf errata DS5 p.8
                         */
                        cur = dpriv->tx_dirty%TX_RING_SIZE;
                        tx_fd = dpriv->tx_fd + cur;
                        skb = dpriv->tx_skbuff[cur];
                        if (skb) {
                                dma_unmap_single(&ppriv->pdev->dev,
                                                 le32_to_cpu(tx_fd->data),
                                                 skb->len, DMA_TO_DEVICE);
                                if (tx_fd->state & FrameEnd) {
                                        dev->stats.tx_packets++;
                                        dev->stats.tx_bytes += skb->len;
                                }
                                dev_consume_skb_irq(skb);
                                dpriv->tx_skbuff[cur] = NULL;
                                ++dpriv->tx_dirty;
                        } else {
                                if (debug > 1)
                                        netdev_err(dev, "Tx: NULL skb %d\n",
                                                   cur);
                        }
                        /*
                         * If the driver ends sending crap on the wire, it
                         * will be way easier to diagnose than the (not so)
                         * random freeze induced by null sized tx frames.
                         */
                        tx_fd->data = tx_fd->next;
                        tx_fd->state = FrameEnd | TO_STATE_TX(2*DUMMY_SKB_SIZE);
                        tx_fd->complete = 0x00000000;
                        tx_fd->jiffies = 0;

                        if (!(state &= ~Alls))
                                goto try;
                }
                /*
                 * Transmit Data Underrun
                 */
                if (state & Xdu) {
                        netdev_err(dev, "Tx Data Underrun. Ask maintainer\n");
                        dpriv->flags = NeedIDT;
                        /* Tx reset */
                        writel(MTFi | Rdt,
                               dpriv->base_addr + 0x0c*dpriv->dev_id + CH0CFG);
                        writel(Action, dpriv->base_addr + GCMDR);
                        return;
                }
                if (state & Cts) {
                        netdev_info(dev, "CTS transition\n");
                        if (!(state &= ~Cts)) /* DEBUG */
                                goto try;
                }
                if (state & Xmr) {
                        /* Frame needs to be sent again - FIXME */
                        netdev_err(dev, "Tx ReTx. Ask maintainer\n");
                        if (!(state &= ~Xmr)) /* DEBUG */
                                goto try;
                }
                if (state & Xpr) {
                        void __iomem *scc_addr;
                        unsigned long ring;
                        unsigned int i;

                        /*
                         * - the busy condition happens (sometimes);
                         * - it doesn't seem to make the handler unreliable.
                         */
                        for (i = 1; i; i <<= 1) {
                                if (!(scc_readl_star(dpriv, dev) & SccBusy))
                                        break;
                        }
                        if (!i)
                                netdev_info(dev, "busy in irq\n");

                        scc_addr = dpriv->base_addr + 0x0c*dpriv->dev_id;
                        /* Keep this order: IDT before IDR */
                        if (dpriv->flags & NeedIDT) {
                                if (debug > 2)
                                        dscc4_tx_print(dev, dpriv, "Xpr");
                                ring = dpriv->tx_fd_dma +
                                       (dpriv->tx_dirty%TX_RING_SIZE)*
                                       sizeof(struct TxFD);
                                writel(ring, scc_addr + CH0BTDA);
                                dscc4_do_tx(dpriv, dev);
                                writel(MTFi | Idt, scc_addr + CH0CFG);
                                if (dscc4_do_action(dev, "IDT") < 0)
                                        goto err_xpr;
                                dpriv->flags &= ~NeedIDT;
                        }
                        if (dpriv->flags & NeedIDR) {
                                ring = dpriv->rx_fd_dma +
                                       (dpriv->rx_current%RX_RING_SIZE)*
                                       sizeof(struct RxFD);
                                writel(ring, scc_addr + CH0BRDA);
                                dscc4_rx_update(dpriv, dev);
                                writel(MTFi | Idr, scc_addr + CH0CFG);
                                if (dscc4_do_action(dev, "IDR") < 0)
                                        goto err_xpr;
                                dpriv->flags &= ~NeedIDR;
                                smp_wmb();
                                /* Activate receiver and misc */
                                scc_writel(0x08050008, dpriv, dev, CCR2);
                        }
                err_xpr:
                        if (!(state &= ~Xpr))
                                goto try;
                }
                if (state & Cd) {
                        if (debug > 0)
                                netdev_info(dev, "CD transition\n");
                        if (!(state &= ~Cd)) /* DEBUG */
                                goto try;
                }
        } else { /* ! SccEvt */
                if (state & Hi) {
#ifdef DSCC4_POLLING
                        while (!dscc4_tx_poll(dpriv, dev));
#endif
                        netdev_info(dev, "Tx Hi\n");
                        state &= ~Hi;
                }
                if (state & Err) {
                        netdev_info(dev, "Tx ERR\n");
                        dev->stats.tx_errors++;
                        state &= ~Err;
                }
        }
        goto try;
}

static void dscc4_rx_irq(struct dscc4_pci_priv *priv,
                                    struct dscc4_dev_priv *dpriv)
{
        struct net_device *dev = dscc4_to_dev(dpriv);
        u32 state;
        int cur;

try:
        cur = dpriv->iqrx_current%IRQ_RING_SIZE;
        state = le32_to_cpu(dpriv->iqrx[cur]);
        if (!state)
                return;
        dpriv->iqrx[cur] = 0;
        dpriv->iqrx_current++;

        if (state_check(state, dpriv, dev, "Rx") < 0)
                return;

        if (!(state & SccEvt)){
                struct RxFD *rx_fd;

                if (debug > 4)
                        printk(KERN_DEBUG "%s: Rx ISR = 0x%08x\n", dev->name,
                               state);
                state &= 0x00ffffff;
                if (state & Err) { /* Hold or reset */
                        printk(KERN_DEBUG "%s: Rx ERR\n", dev->name);
                        cur = dpriv->rx_current%RX_RING_SIZE;
                        rx_fd = dpriv->rx_fd + cur;
                        /*
                         * Presume we're not facing a DMAC receiver reset.
                         * As We use the rx size-filtering feature of the
                         * DSCC4, the beginning of a new frame is waiting in
                         * the rx fifo. I bet a Receive Data Overflow will
                         * happen most of time but let's try and avoid it.
                         * Btw (as for RDO) if one experiences ERR whereas
                         * the system looks rather idle, there may be a
                         * problem with latency. In this case, increasing
                         * RX_RING_SIZE may help.
                         */
                        //while (dpriv->rx_needs_refill) {
                                while (!(rx_fd->state1 & Hold)) {
                                        rx_fd++;
                                        cur++;
                                        if (!(cur = cur%RX_RING_SIZE))
                                                rx_fd = dpriv->rx_fd;
                                }
                                //dpriv->rx_needs_refill--;
                                try_get_rx_skb(dpriv, dev);
                                if (!rx_fd->data)
                                        goto try;
                                rx_fd->state1 &= ~Hold;
                                rx_fd->state2 = 0x00000000;
                                rx_fd->end = cpu_to_le32(0xbabeface);
                        //}
                        goto try;
                }
                if (state & Fi) {
                        dscc4_rx_skb(dpriv, dev);
                        goto try;
                }
                if (state & Hi ) { /* HI bit */
                        netdev_info(dev, "Rx Hi\n");
                        state &= ~Hi;
                        goto try;
                }
        } else { /* SccEvt */
                if (debug > 1) {
                        //FIXME: verifier la presence de tous les evenements
                        static struct {
                                u32 mask;
                                const char *irq_name;
                        } evts[] = {
                                { 0x00008000, "TIN"},
                                { 0x00000020, "RSC"},
                                { 0x00000010, "PCE"},
                                { 0x00000008, "PLLA"},
                                { 0, NULL}
                        }, *evt;

                        for (evt = evts; evt->irq_name; evt++) {
                                if (state & evt->mask) {
                                        printk(KERN_DEBUG "%s: %s\n",
                                               dev->name, evt->irq_name);
                                        if (!(state &= ~evt->mask))
                                                goto try;
                                }
                        }
                } else {
                        if (!(state &= ~0x0000c03c))
                                goto try;
                }
                if (state & Cts) {
                        netdev_info(dev, "CTS transition\n");
                        if (!(state &= ~Cts)) /* DEBUG */
                                goto try;
                }
                /*
                 * Receive Data Overflow (FIXME: fscked)
                 */
                if (state & Rdo) {
                        struct RxFD *rx_fd;
                        void __iomem *scc_addr;
                        int cur;

                        //if (debug)
                        //      dscc4_rx_dump(dpriv);
                        scc_addr = dpriv->base_addr + 0x0c*dpriv->dev_id;

                        scc_patchl(RxActivate, 0, dpriv, dev, CCR2);
                        /*
                         * This has no effect. Why ?
                         * ORed with TxSccRes, one sees the CFG ack (for
                         * the TX part only).
                         */
                        scc_writel(RxSccRes, dpriv, dev, CMDR);
                        dpriv->flags |= RdoSet;

                        /*
                         * Let's try and save something in the received data.
                         * rx_current must be incremented at least once to
                         * avoid HOLD in the BRDA-to-be-pointed desc.
                         */
                        do {
                                cur = dpriv->rx_current++%RX_RING_SIZE;
                                rx_fd = dpriv->rx_fd + cur;
                                if (!(rx_fd->state2 & DataComplete))
                                        break;
                                if (rx_fd->state2 & FrameAborted) {
                                        dev->stats.rx_over_errors++;
                                        rx_fd->state1 |= Hold;
                                        rx_fd->state2 = 0x00000000;
                                        rx_fd->end = cpu_to_le32(0xbabeface);
                                } else
                                        dscc4_rx_skb(dpriv, dev);
                        } while (1);

                        if (debug > 0) {
                                if (dpriv->flags & RdoSet)
                                        printk(KERN_DEBUG
                                               "%s: no RDO in Rx data\n", DRV_NAME);
                        }
#ifdef DSCC4_RDO_EXPERIMENTAL_RECOVERY
                        /*
                         * FIXME: must the reset be this violent ?
                         */
#warning "FIXME: CH0BRDA"
                        writel(dpriv->rx_fd_dma +
                               (dpriv->rx_current%RX_RING_SIZE)*
                               sizeof(struct RxFD), scc_addr + CH0BRDA);
                        writel(MTFi|Rdr|Idr, scc_addr + CH0CFG);
                        if (dscc4_do_action(dev, "RDR") < 0) {
                                netdev_err(dev, "RDO recovery failed(RDR)\n");
                                goto rdo_end;
                        }
                        writel(MTFi|Idr, scc_addr + CH0CFG);
                        if (dscc4_do_action(dev, "IDR") < 0) {
                                netdev_err(dev, "RDO recovery failed(IDR)\n");
                                goto rdo_end;
                        }
                rdo_end:
#endif
                        scc_patchl(0, RxActivate, dpriv, dev, CCR2);
                        goto try;
                }
                if (state & Cd) {
                        netdev_info(dev, "CD transition\n");
                        if (!(state &= ~Cd)) /* DEBUG */
                                goto try;
                }
                if (state & Flex) {
                        printk(KERN_DEBUG "%s: Flex. Ttttt...\n", DRV_NAME);
                        if (!(state &= ~Flex))
                                goto try;
                }
        }
}

/*
 * I had expected the following to work for the first descriptor
 * (tx_fd->state = 0xc0000000)
 * - Hold=1 (don't try and branch to the next descripto);
 * - No=0 (I want an empty data section, i.e. size=0);
 * - Fe=1 (required by No=0 or we got an Err irq and must reset).
 * It failed and locked solid. Thus the introduction of a dummy skb.
 * Problem is acknowledged in errata sheet DS5. Joy :o/
 */
static struct sk_buff *dscc4_init_dummy_skb(struct dscc4_dev_priv *dpriv)
{
        struct sk_buff *skb;

        skb = dev_alloc_skb(DUMMY_SKB_SIZE);
        if (skb) {
                struct device *d = &dpriv->pci_priv->pdev->dev;
                int last = dpriv->tx_dirty%TX_RING_SIZE;
                struct TxFD *tx_fd = dpriv->tx_fd + last;
                dma_addr_t addr;

                skb->len = DUMMY_SKB_SIZE;
                skb_copy_to_linear_data(skb, version,
                                        strlen(version) % DUMMY_SKB_SIZE);
                addr = dma_map_single(d, skb->data, DUMMY_SKB_SIZE,
                                      DMA_TO_DEVICE);
                if (dma_mapping_error(d, addr)) {
                        dev_kfree_skb_any(skb);
                        return NULL;
                }
                tx_fd->state = FrameEnd | TO_STATE_TX(DUMMY_SKB_SIZE);
                tx_fd->data = cpu_to_le32(addr);
                dpriv->tx_skbuff[last] = skb;
        }
        return skb;
}

static int dscc4_init_ring(struct net_device *dev)
{
        struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
        struct device *d = &dpriv->pci_priv->pdev->dev;
        struct TxFD *tx_fd;
        struct RxFD *rx_fd;
        void *ring;
        int i;

        ring = dma_alloc_coherent(d, RX_TOTAL_SIZE, &dpriv->rx_fd_dma,
                                  GFP_KERNEL);
        if (!ring)
                goto err_out;
        dpriv->rx_fd = rx_fd = (struct RxFD *) ring;

        ring = dma_alloc_coherent(d, TX_TOTAL_SIZE, &dpriv->tx_fd_dma,
                                  GFP_KERNEL);
        if (!ring)
                goto err_free_dma_rx;
        dpriv->tx_fd = tx_fd = (struct TxFD *) ring;

        memset(dpriv->tx_skbuff, 0, sizeof(struct sk_buff *)*TX_RING_SIZE);
        dpriv->tx_dirty = 0xffffffff;
        i = dpriv->tx_current = 0;
        do {
                tx_fd->state = FrameEnd | TO_STATE_TX(2*DUMMY_SKB_SIZE);
                tx_fd->complete = 0x00000000;
                /* FIXME: NULL should be ok - to be tried */
                tx_fd->data = cpu_to_le32(dpriv->tx_fd_dma);
                (tx_fd++)->next = cpu_to_le32(dpriv->tx_fd_dma +
                                        (++i%TX_RING_SIZE)*sizeof(*tx_fd));
        } while (i < TX_RING_SIZE);

        if (!dscc4_init_dummy_skb(dpriv))
                goto err_free_dma_tx;

        memset(dpriv->rx_skbuff, 0, sizeof(struct sk_buff *)*RX_RING_SIZE);
        i = dpriv->rx_dirty = dpriv->rx_current = 0;
        do {
                /* size set by the host. Multiple of 4 bytes please */
                rx_fd->state1 = HiDesc;
                rx_fd->state2 = 0x00000000;
                rx_fd->end = cpu_to_le32(0xbabeface);
                rx_fd->state1 |= TO_STATE_RX(HDLC_MAX_MRU);
                // FIXME: return value verifiee mais traitement suspect
                if (try_get_rx_skb(dpriv, dev) >= 0)
                        dpriv->rx_dirty++;
                (rx_fd++)->next = cpu_to_le32(dpriv->rx_fd_dma +
                                        (++i%RX_RING_SIZE)*sizeof(*rx_fd));
        } while (i < RX_RING_SIZE);

        return 0;

err_free_dma_tx:
        dma_free_coherent(d, TX_TOTAL_SIZE, ring, dpriv->tx_fd_dma);
err_free_dma_rx:
        dma_free_coherent(d, RX_TOTAL_SIZE, rx_fd, dpriv->rx_fd_dma);
err_out:
        return -ENOMEM;
}

static void dscc4_remove_one(struct pci_dev *pdev)
{
        struct dscc4_pci_priv *ppriv;
        struct dscc4_dev_priv *root;
        void __iomem *ioaddr;
        int i;

        ppriv = pci_get_drvdata(pdev);
        root = ppriv->root;

        ioaddr = root->base_addr;

        dscc4_pci_reset(pdev, ioaddr);

        free_irq(pdev->irq, root);
        dma_free_coherent(&pdev->dev, IRQ_RING_SIZE*sizeof(u32), ppriv->iqcfg,
                          ppriv->iqcfg_dma);
        for (i = 0; i < dev_per_card; i++) {
                struct dscc4_dev_priv *dpriv = root + i;

                dscc4_release_ring(dpriv);
                dma_free_coherent(&pdev->dev, IRQ_RING_SIZE*sizeof(u32),
                                  dpriv->iqrx, dpriv->iqrx_dma);
                dma_free_coherent(&pdev->dev, IRQ_RING_SIZE*sizeof(u32),
                                  dpriv->iqtx, dpriv->iqtx_dma);
        }

        dscc4_free1(pdev);

        iounmap(ioaddr);

        pci_release_region(pdev, 1);

        pci_release_region(pdev, 0);

        pci_disable_device(pdev);
}

static int dscc4_hdlc_attach(struct net_device *dev, unsigned short encoding,
        unsigned short parity)
{
        struct dscc4_dev_priv *dpriv = dscc4_priv(dev);

        if (encoding != ENCODING_NRZ &&
            encoding != ENCODING_NRZI &&
            encoding != ENCODING_FM_MARK &&
            encoding != ENCODING_FM_SPACE &&
            encoding != ENCODING_MANCHESTER)
                return -EINVAL;

        if (parity != PARITY_NONE &&
            parity != PARITY_CRC16_PR0_CCITT &&
            parity != PARITY_CRC16_PR1_CCITT &&
            parity != PARITY_CRC32_PR0_CCITT &&
            parity != PARITY_CRC32_PR1_CCITT)
                return -EINVAL;

        dpriv->encoding = encoding;
        dpriv->parity = parity;
        return 0;
}

#ifndef MODULE
static int __init dscc4_setup(char *str)
{
        int *args[] = { &debug, &quartz, NULL }, **p = args;

        while (*p && (get_option(&str, *p) == 2))
                p++;
        return 1;
}

__setup("dscc4.setup=", dscc4_setup);
#endif

static const struct pci_device_id dscc4_pci_tbl[] = {
        { PCI_VENDOR_ID_SIEMENS, PCI_DEVICE_ID_SIEMENS_DSCC4,
                PCI_ANY_ID, PCI_ANY_ID, },
        { 0,}
};
MODULE_DEVICE_TABLE(pci, dscc4_pci_tbl);

static struct pci_driver dscc4_driver = {
        .name           = DRV_NAME,
        .id_table       = dscc4_pci_tbl,
        .probe          = dscc4_init_one,
        .remove         = dscc4_remove_one,
};

module_pci_driver(dscc4_driver);