// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *
 *      (c) Copyright 1998 Alan Cox <alan@lxorguk.ukuu.org.uk>
 *      (c) Copyright 2000, 2001 Red Hat Inc
 *
 *      Development of this driver was funded by Equiinet Ltd
 *                      http://www.equiinet.com
 *
 *      ChangeLog:
 *
 *      Asynchronous mode dropped for 2.2. For 2.5 we will attempt the
 *      unification of all the Z85x30 asynchronous drivers for real.
 *
 *      DMA now uses get_free_page as kmalloc buffers may span a 64K 
 *      boundary.
 *
 *      Modified for SMP safety and SMP locking by Alan Cox
 *                                      <alan@lxorguk.ukuu.org.uk>
 *
 *      Performance
 *
 *      Z85230:
 *      Non DMA you want a 486DX50 or better to do 64Kbits. 9600 baud
 *      X.25 is not unrealistic on all machines. DMA mode can in theory
 *      handle T1/E1 quite nicely. In practice the limit seems to be about
 *      512Kbit->1Mbit depending on motherboard.
 *
 *      Z85C30:
 *      64K will take DMA, 9600 baud X.25 should be ok.
 *
 *      Z8530:
 *      Synchronous mode without DMA is unlikely to pass about 2400 baud.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/delay.h>
#include <linux/hdlc.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/gfp.h>
#include <asm/dma.h>
#include <asm/io.h>
#define RT_LOCK
#define RT_UNLOCK
#include <linux/spinlock.h>

#include "z85230.h"


/**
 *      z8530_read_port - Architecture specific interface function
 *      @p: port to read
 *
 *      Provided port access methods. The Comtrol SV11 requires no delays
 *      between accesses and uses PC I/O. Some drivers may need a 5uS delay
 *      
 *      In the longer term this should become an architecture specific
 *      section so that this can become a generic driver interface for all
 *      platforms. For now we only handle PC I/O ports with or without the
 *      dread 5uS sanity delay.
 *
 *      The caller must hold sufficient locks to avoid violating the horrible
 *      5uS delay rule.
 */

static inline int z8530_read_port(unsigned long p)
{
        u8 r=inb(Z8530_PORT_OF(p));
        if(p&Z8530_PORT_SLEEP)  /* gcc should figure this out efficiently ! */
                udelay(5);
        return r;
}

/**
 *      z8530_write_port - Architecture specific interface function
 *      @p: port to write
 *      @d: value to write
 *
 *      Write a value to a port with delays if need be. Note that the
 *      caller must hold locks to avoid read/writes from other contexts
 *      violating the 5uS rule
 *
 *      In the longer term this should become an architecture specific
 *      section so that this can become a generic driver interface for all
 *      platforms. For now we only handle PC I/O ports with or without the
 *      dread 5uS sanity delay.
 */


static inline void z8530_write_port(unsigned long p, u8 d)
{
        outb(d,Z8530_PORT_OF(p));
        if(p&Z8530_PORT_SLEEP)
                udelay(5);
}



static void z8530_rx_done(struct z8530_channel *c);
static void z8530_tx_done(struct z8530_channel *c);


/**
 *      read_zsreg - Read a register from a Z85230 
 *      @c: Z8530 channel to read from (2 per chip)
 *      @reg: Register to read
 *      FIXME: Use a spinlock.
 *      
 *      Most of the Z8530 registers are indexed off the control registers.
 *      A read is done by writing to the control register and reading the
 *      register back.  The caller must hold the lock
 */
 
static inline u8 read_zsreg(struct z8530_channel *c, u8 reg)
{
        if(reg)
                z8530_write_port(c->ctrlio, reg);
        return z8530_read_port(c->ctrlio);
}

/**
 *      read_zsdata - Read the data port of a Z8530 channel
 *      @c: The Z8530 channel to read the data port from
 *
 *      The data port provides fast access to some things. We still
 *      have all the 5uS delays to worry about.
 */

static inline u8 read_zsdata(struct z8530_channel *c)
{
        u8 r;
        r=z8530_read_port(c->dataio);
        return r;
}

/**
 *      write_zsreg - Write to a Z8530 channel register
 *      @c: The Z8530 channel
 *      @reg: Register number
 *      @val: Value to write
 *
 *      Write a value to an indexed register. The caller must hold the lock
 *      to honour the irritating delay rules. We know about register 0
 *      being fast to access.
 *
 *      Assumes c->lock is held.
 */
static inline void write_zsreg(struct z8530_channel *c, u8 reg, u8 val)
{
        if(reg)
                z8530_write_port(c->ctrlio, reg);
        z8530_write_port(c->ctrlio, val);

}

/**
 *      write_zsctrl - Write to a Z8530 control register
 *      @c: The Z8530 channel
 *      @val: Value to write
 *
 *      Write directly to the control register on the Z8530
 */

static inline void write_zsctrl(struct z8530_channel *c, u8 val)
{
        z8530_write_port(c->ctrlio, val);
}

/**
 *      write_zsdata - Write to a Z8530 control register
 *      @c: The Z8530 channel
 *      @val: Value to write
 *
 *      Write directly to the data register on the Z8530
 */


static inline void write_zsdata(struct z8530_channel *c, u8 val)
{
        z8530_write_port(c->dataio, val);
}

/*
 *      Register loading parameters for a dead port
 */
 
u8 z8530_dead_port[]=
{
        255
};

EXPORT_SYMBOL(z8530_dead_port);

/*
 *      Register loading parameters for currently supported circuit types
 */


/*
 *      Data clocked by telco end. This is the correct data for the UK
 *      "kilostream" service, and most other similar services.
 */
 
u8 z8530_hdlc_kilostream[]=
{
        4,      SYNC_ENAB|SDLC|X1CLK,
        2,      0,      /* No vector */
        1,      0,
        3,      ENT_HM|RxCRC_ENAB|Rx8,
        5,      TxCRC_ENAB|RTS|TxENAB|Tx8|DTR,
        9,      0,              /* Disable interrupts */
        6,      0xFF,
        7,      FLAG,
        10,     ABUNDER|NRZ|CRCPS,/*MARKIDLE ??*/
        11,     TCTRxCP,
        14,     DISDPLL,
        15,     DCDIE|SYNCIE|CTSIE|TxUIE|BRKIE,
        1,      EXT_INT_ENAB|TxINT_ENAB|INT_ALL_Rx,
        9,      NV|MIE|NORESET,
        255
};

EXPORT_SYMBOL(z8530_hdlc_kilostream);

/*
 *      As above but for enhanced chips.
 */
 
u8 z8530_hdlc_kilostream_85230[]=
{
        4,      SYNC_ENAB|SDLC|X1CLK,
        2,      0,      /* No vector */
        1,      0,
        3,      ENT_HM|RxCRC_ENAB|Rx8,
        5,      TxCRC_ENAB|RTS|TxENAB|Tx8|DTR,
        9,      0,              /* Disable interrupts */
        6,      0xFF,
        7,      FLAG,
        10,     ABUNDER|NRZ|CRCPS,      /* MARKIDLE?? */
        11,     TCTRxCP,
        14,     DISDPLL,
        15,     DCDIE|SYNCIE|CTSIE|TxUIE|BRKIE,
        1,      EXT_INT_ENAB|TxINT_ENAB|INT_ALL_Rx,
        9,      NV|MIE|NORESET,
        23,     3,              /* Extended mode AUTO TX and EOM*/
        
        255
};

EXPORT_SYMBOL(z8530_hdlc_kilostream_85230);

/**
 *      z8530_flush_fifo - Flush on chip RX FIFO
 *      @c: Channel to flush
 *
 *      Flush the receive FIFO. There is no specific option for this, we 
 *      blindly read bytes and discard them. Reading when there is no data
 *      is harmless. The 8530 has a 4 byte FIFO, the 85230 has 8 bytes.
 *      
 *      All locking is handled for the caller. On return data may still be
 *      present if it arrived during the flush.
 */
 
static void z8530_flush_fifo(struct z8530_channel *c)
{
        read_zsreg(c, R1);
        read_zsreg(c, R1);
        read_zsreg(c, R1);
        read_zsreg(c, R1);
        if(c->dev->type==Z85230)
        {
                read_zsreg(c, R1);
                read_zsreg(c, R1);
                read_zsreg(c, R1);
                read_zsreg(c, R1);
        }
}       

/**
 *      z8530_rtsdtr - Control the outgoing DTS/RTS line
 *      @c: The Z8530 channel to control;
 *      @set: 1 to set, 0 to clear
 *
 *      Sets or clears DTR/RTS on the requested line. All locking is handled
 *      by the caller. For now we assume all boards use the actual RTS/DTR
 *      on the chip. Apparently one or two don't. We'll scream about them
 *      later.
 */

static void z8530_rtsdtr(struct z8530_channel *c, int set)
{
        if (set)
                c->regs[5] |= (RTS | DTR);
        else
                c->regs[5] &= ~(RTS | DTR);
        write_zsreg(c, R5, c->regs[5]);
}

/**
 *      z8530_rx - Handle a PIO receive event
 *      @c: Z8530 channel to process
 *
 *      Receive handler for receiving in PIO mode. This is much like the 
 *      async one but not quite the same or as complex
 *
 *      Note: Its intended that this handler can easily be separated from
 *      the main code to run realtime. That'll be needed for some machines
 *      (eg to ever clock 64kbits on a sparc ;)).
 *
 *      The RT_LOCK macros don't do anything now. Keep the code covered
 *      by them as short as possible in all circumstances - clocks cost
 *      baud. The interrupt handler is assumed to be atomic w.r.t. to
 *      other code - this is true in the RT case too.
 *
 *      We only cover the sync cases for this. If you want 2Mbit async
 *      do it yourself but consider medical assistance first. This non DMA 
 *      synchronous mode is portable code. The DMA mode assumes PCI like 
 *      ISA DMA
 *
 *      Called with the device lock held
 */
 
static void z8530_rx(struct z8530_channel *c)
{
        u8 ch,stat;

        while(1)
        {
                /* FIFO empty ? */
                if(!(read_zsreg(c, R0)&1))
                        break;
                ch=read_zsdata(c);
                stat=read_zsreg(c, R1);
        
                /*
                 *      Overrun ?
                 */
                if(c->count < c->max)
                {
                        *c->dptr++=ch;
                        c->count++;
                }

                if(stat&END_FR)
                {
                
                        /*
                         *      Error ?
                         */
                        if(stat&(Rx_OVR|CRC_ERR))
                        {
                                /* Rewind the buffer and return */
                                if(c->skb)
                                        c->dptr=c->skb->data;
                                c->count=0;
                                if(stat&Rx_OVR)
                                {
                                        pr_warn("%s: overrun\n", c->dev->name);
                                        c->rx_overrun++;
                                }
                                if(stat&CRC_ERR)
                                {
                                        c->rx_crc_err++;
                                        /* printk("crc error\n"); */
                                }
                                /* Shove the frame upstream */
                        }
                        else
                        {
                                /*
                                 *      Drop the lock for RX processing, or
                                 *      there are deadlocks
                                 */
                                z8530_rx_done(c);
                                write_zsctrl(c, RES_Rx_CRC);
                        }
                }
        }
        /*
         *      Clear irq
         */
        write_zsctrl(c, ERR_RES);
        write_zsctrl(c, RES_H_IUS);
}


/**
 *      z8530_tx - Handle a PIO transmit event
 *      @c: Z8530 channel to process
 *
 *      Z8530 transmit interrupt handler for the PIO mode. The basic
 *      idea is to attempt to keep the FIFO fed. We fill as many bytes
 *      in as possible, its quite possible that we won't keep up with the
 *      data rate otherwise.
 */
 
static void z8530_tx(struct z8530_channel *c)
{
        while(c->txcount) {
                /* FIFO full ? */
                if(!(read_zsreg(c, R0)&4))
                        return;
                c->txcount--;
                /*
                 *      Shovel out the byte
                 */
                write_zsreg(c, R8, *c->tx_ptr++);
                write_zsctrl(c, RES_H_IUS);
                /* We are about to underflow */
                if(c->txcount==0)
                {
                        write_zsctrl(c, RES_EOM_L);
                        write_zsreg(c, R10, c->regs[10]&~ABUNDER);
                }
        }

        
        /*
         *      End of frame TX - fire another one
         */
         
        write_zsctrl(c, RES_Tx_P);

        z8530_tx_done(c);        
        write_zsctrl(c, RES_H_IUS);
}

/**
 *      z8530_status - Handle a PIO status exception
 *      @chan: Z8530 channel to process
 *
 *      A status event occurred in PIO synchronous mode. There are several
 *      reasons the chip will bother us here. A transmit underrun means we
 *      failed to feed the chip fast enough and just broke a packet. A DCD
 *      change is a line up or down.
 */

static void z8530_status(struct z8530_channel *chan)
{
        u8 status, altered;

        status = read_zsreg(chan, R0);
        altered = chan->status ^ status;

        chan->status = status;

        if (status & TxEOM) {
/*              printk("%s: Tx underrun.\n", chan->dev->name); */
                chan->netdevice->stats.tx_fifo_errors++;
                write_zsctrl(chan, ERR_RES);
                z8530_tx_done(chan);
        }

        if (altered & chan->dcdcheck)
        {
                if (status & chan->dcdcheck) {
                        pr_info("%s: DCD raised\n", chan->dev->name);
                        write_zsreg(chan, R3, chan->regs[3] | RxENABLE);
                        if (chan->netdevice)
                                netif_carrier_on(chan->netdevice);
                } else {
                        pr_info("%s: DCD lost\n", chan->dev->name);
                        write_zsreg(chan, R3, chan->regs[3] & ~RxENABLE);
                        z8530_flush_fifo(chan);
                        if (chan->netdevice)
                                netif_carrier_off(chan->netdevice);
                }

        }
        write_zsctrl(chan, RES_EXT_INT);
        write_zsctrl(chan, RES_H_IUS);
}

struct z8530_irqhandler z8530_sync = {
        .rx = z8530_rx,
        .tx = z8530_tx,
        .status = z8530_status,
};

EXPORT_SYMBOL(z8530_sync);

/**
 *      z8530_dma_rx - Handle a DMA RX event
 *      @chan: Channel to handle
 *
 *      Non bus mastering DMA interfaces for the Z8x30 devices. This
 *      is really pretty PC specific. The DMA mode means that most receive
 *      events are handled by the DMA hardware. We get a kick here only if
 *      a frame ended.
 */
 
static void z8530_dma_rx(struct z8530_channel *chan)
{
        if(chan->rxdma_on)
        {
                /* Special condition check only */
                u8 status;
        
                read_zsreg(chan, R7);
                read_zsreg(chan, R6);
                
                status=read_zsreg(chan, R1);
        
                if(status&END_FR)
                {
                        z8530_rx_done(chan);    /* Fire up the next one */
                }               
                write_zsctrl(chan, ERR_RES);
                write_zsctrl(chan, RES_H_IUS);
        }
        else
        {
                /* DMA is off right now, drain the slow way */
                z8530_rx(chan);
        }       
}

/**
 *      z8530_dma_tx - Handle a DMA TX event
 *      @chan:  The Z8530 channel to handle
 *
 *      We have received an interrupt while doing DMA transmissions. It
 *      shouldn't happen. Scream loudly if it does.
 */
 
static void z8530_dma_tx(struct z8530_channel *chan)
{
        if(!chan->dma_tx)
        {
                pr_warn("Hey who turned the DMA off?\n");
                z8530_tx(chan);
                return;
        }
        /* This shouldn't occur in DMA mode */
        pr_err("DMA tx - bogus event!\n");
        z8530_tx(chan);
}

/**
 *      z8530_dma_status - Handle a DMA status exception
 *      @chan: Z8530 channel to process
 *      
 *      A status event occurred on the Z8530. We receive these for two reasons
 *      when in DMA mode. Firstly if we finished a packet transfer we get one
 *      and kick the next packet out. Secondly we may see a DCD change.
 *
 */
 
static void z8530_dma_status(struct z8530_channel *chan)
{
        u8 status, altered;

        status=read_zsreg(chan, R0);
        altered=chan->status^status;
        
        chan->status=status;


        if(chan->dma_tx)
        {
                if(status&TxEOM)
                {
                        unsigned long flags;
        
                        flags=claim_dma_lock();
                        disable_dma(chan->txdma);
                        clear_dma_ff(chan->txdma);      
                        chan->txdma_on=0;
                        release_dma_lock(flags);
                        z8530_tx_done(chan);
                }
        }

        if (altered & chan->dcdcheck)
        {
                if (status & chan->dcdcheck) {
                        pr_info("%s: DCD raised\n", chan->dev->name);
                        write_zsreg(chan, R3, chan->regs[3] | RxENABLE);
                        if (chan->netdevice)
                                netif_carrier_on(chan->netdevice);
                } else {
                        pr_info("%s: DCD lost\n", chan->dev->name);
                        write_zsreg(chan, R3, chan->regs[3] & ~RxENABLE);
                        z8530_flush_fifo(chan);
                        if (chan->netdevice)
                                netif_carrier_off(chan->netdevice);
                }
        }

        write_zsctrl(chan, RES_EXT_INT);
        write_zsctrl(chan, RES_H_IUS);
}

static struct z8530_irqhandler z8530_dma_sync = {
        .rx = z8530_dma_rx,
        .tx = z8530_dma_tx,
        .status = z8530_dma_status,
};

static struct z8530_irqhandler z8530_txdma_sync = {
        .rx = z8530_rx,
        .tx = z8530_dma_tx,
        .status = z8530_dma_status,
};

/**
 *      z8530_rx_clear - Handle RX events from a stopped chip
 *      @c: Z8530 channel to shut up
 *
 *      Receive interrupt vectors for a Z8530 that is in 'parked' mode.
 *      For machines with PCI Z85x30 cards, or level triggered interrupts
 *      (eg the MacII) we must clear the interrupt cause or die.
 */


static void z8530_rx_clear(struct z8530_channel *c)
{
        /*
         *      Data and status bytes
         */
        u8 stat;

        read_zsdata(c);
        stat=read_zsreg(c, R1);
        
        if(stat&END_FR)
                write_zsctrl(c, RES_Rx_CRC);
        /*
         *      Clear irq
         */
        write_zsctrl(c, ERR_RES);
        write_zsctrl(c, RES_H_IUS);
}

/**
 *      z8530_tx_clear - Handle TX events from a stopped chip
 *      @c: Z8530 channel to shut up
 *
 *      Transmit interrupt vectors for a Z8530 that is in 'parked' mode.
 *      For machines with PCI Z85x30 cards, or level triggered interrupts
 *      (eg the MacII) we must clear the interrupt cause or die.
 */

static void z8530_tx_clear(struct z8530_channel *c)
{
        write_zsctrl(c, RES_Tx_P);
        write_zsctrl(c, RES_H_IUS);
}

/**
 *      z8530_status_clear - Handle status events from a stopped chip
 *      @chan: Z8530 channel to shut up
 *
 *      Status interrupt vectors for a Z8530 that is in 'parked' mode.
 *      For machines with PCI Z85x30 cards, or level triggered interrupts
 *      (eg the MacII) we must clear the interrupt cause or die.
 */

static void z8530_status_clear(struct z8530_channel *chan)
{
        u8 status=read_zsreg(chan, R0);
        if(status&TxEOM)
                write_zsctrl(chan, ERR_RES);
        write_zsctrl(chan, RES_EXT_INT);
        write_zsctrl(chan, RES_H_IUS);
}

struct z8530_irqhandler z8530_nop = {
        .rx = z8530_rx_clear,
        .tx = z8530_tx_clear,
        .status = z8530_status_clear,
};


EXPORT_SYMBOL(z8530_nop);

/**
 *      z8530_interrupt - Handle an interrupt from a Z8530
 *      @irq:   Interrupt number
 *      @dev_id: The Z8530 device that is interrupting.
 *
 *      A Z85[2]30 device has stuck its hand in the air for attention.
 *      We scan both the channels on the chip for events and then call
 *      the channel specific call backs for each channel that has events.
 *      We have to use callback functions because the two channels can be
 *      in different modes.
 *
 *      Locking is done for the handlers. Note that locking is done
 *      at the chip level (the 5uS delay issue is per chip not per
 *      channel). c->lock for both channels points to dev->lock
 */

irqreturn_t z8530_interrupt(int irq, void *dev_id)
{
        struct z8530_dev *dev=dev_id;
        u8 intr;
        static volatile int locker=0;
        int work=0;
        struct z8530_irqhandler *irqs;
        
        if(locker)
        {
                pr_err("IRQ re-enter\n");
                return IRQ_NONE;
        }
        locker=1;

        spin_lock(&dev->lock);

        while(++work<5000)
        {

                intr = read_zsreg(&dev->chanA, R3);
                if(!(intr & (CHARxIP|CHATxIP|CHAEXT|CHBRxIP|CHBTxIP|CHBEXT)))
                        break;
        
                /* This holds the IRQ status. On the 8530 you must read it from chan 
                   A even though it applies to the whole chip */
                
                /* Now walk the chip and see what it is wanting - it may be
                   an IRQ for someone else remember */
                   
                irqs=dev->chanA.irqs;

                if(intr & (CHARxIP|CHATxIP|CHAEXT))
                {
                        if(intr&CHARxIP)
                                irqs->rx(&dev->chanA);
                        if(intr&CHATxIP)
                                irqs->tx(&dev->chanA);
                        if(intr&CHAEXT)
                                irqs->status(&dev->chanA);
                }

                irqs=dev->chanB.irqs;

                if(intr & (CHBRxIP|CHBTxIP|CHBEXT))
                {
                        if(intr&CHBRxIP)
                                irqs->rx(&dev->chanB);
                        if(intr&CHBTxIP)
                                irqs->tx(&dev->chanB);
                        if(intr&CHBEXT)
                                irqs->status(&dev->chanB);
                }
        }
        spin_unlock(&dev->lock);
        if(work==5000)
                pr_err("%s: interrupt jammed - abort(0x%X)!\n",
                       dev->name, intr);
        /* Ok all done */
        locker=0;
        return IRQ_HANDLED;
}

EXPORT_SYMBOL(z8530_interrupt);

static const u8 reg_init[16]=
{
        0,0,0,0,
        0,0,0,0,
        0,0,0,0,
        0x55,0,0,0
};


/**
 *      z8530_sync_open - Open a Z8530 channel for PIO
 *      @dev:   The network interface we are using
 *      @c:     The Z8530 channel to open in synchronous PIO mode
 *
 *      Switch a Z8530 into synchronous mode without DMA assist. We
 *      raise the RTS/DTR and commence network operation.
 */
 
int z8530_sync_open(struct net_device *dev, struct z8530_channel *c)
{
        unsigned long flags;

        spin_lock_irqsave(c->lock, flags);

        c->sync = 1;
        c->mtu = dev->mtu+64;
        c->count = 0;
        c->skb = NULL;
        c->skb2 = NULL;
        c->irqs = &z8530_sync;

        /* This loads the double buffer up */
        z8530_rx_done(c);       /* Load the frame ring */
        z8530_rx_done(c);       /* Load the backup frame */
        z8530_rtsdtr(c,1);
        c->dma_tx = 0;
        c->regs[R1]|=TxINT_ENAB;
        write_zsreg(c, R1, c->regs[R1]);
        write_zsreg(c, R3, c->regs[R3]|RxENABLE);

        spin_unlock_irqrestore(c->lock, flags);
        return 0;
}


EXPORT_SYMBOL(z8530_sync_open);

/**
 *      z8530_sync_close - Close a PIO Z8530 channel
 *      @dev: Network device to close
 *      @c: Z8530 channel to disassociate and move to idle
 *
 *      Close down a Z8530 interface and switch its interrupt handlers
 *      to discard future events.
 */
 
int z8530_sync_close(struct net_device *dev, struct z8530_channel *c)
{
        u8 chk;
        unsigned long flags;
        
        spin_lock_irqsave(c->lock, flags);
        c->irqs = &z8530_nop;
        c->max = 0;
        c->sync = 0;
        
        chk=read_zsreg(c,R0);
        write_zsreg(c, R3, c->regs[R3]);
        z8530_rtsdtr(c,0);

        spin_unlock_irqrestore(c->lock, flags);
        return 0;
}

EXPORT_SYMBOL(z8530_sync_close);

/**
 *      z8530_sync_dma_open - Open a Z8530 for DMA I/O
 *      @dev: The network device to attach
 *      @c: The Z8530 channel to configure in sync DMA mode.
 *
 *      Set up a Z85x30 device for synchronous DMA in both directions. Two
 *      ISA DMA channels must be available for this to work. We assume ISA
 *      DMA driven I/O and PC limits on access.
 */
 
int z8530_sync_dma_open(struct net_device *dev, struct z8530_channel *c)
{
        unsigned long cflags, dflags;
        
        c->sync = 1;
        c->mtu = dev->mtu+64;
        c->count = 0;
        c->skb = NULL;
        c->skb2 = NULL;
        /*
         *      Load the DMA interfaces up
         */
        c->rxdma_on = 0;
        c->txdma_on = 0;
        
        /*
         *      Allocate the DMA flip buffers. Limit by page size.
         *      Everyone runs 1500 mtu or less on wan links so this
         *      should be fine.
         */
         
        if(c->mtu  > PAGE_SIZE/2)
                return -EMSGSIZE;
         
        c->rx_buf[0]=(void *)get_zeroed_page(GFP_KERNEL|GFP_DMA);
        if(c->rx_buf[0]==NULL)
                return -ENOBUFS;
        c->rx_buf[1]=c->rx_buf[0]+PAGE_SIZE/2;
        
        c->tx_dma_buf[0]=(void *)get_zeroed_page(GFP_KERNEL|GFP_DMA);
        if(c->tx_dma_buf[0]==NULL)
        {
                free_page((unsigned long)c->rx_buf[0]);
                c->rx_buf[0]=NULL;
                return -ENOBUFS;
        }
        c->tx_dma_buf[1]=c->tx_dma_buf[0]+PAGE_SIZE/2;

        c->tx_dma_used=0;
        c->dma_tx = 1;
        c->dma_num=0;
        c->dma_ready=1;
        
        /*
         *      Enable DMA control mode
         */

        spin_lock_irqsave(c->lock, cflags);
         
        /*
         *      TX DMA via DIR/REQ
         */
         
        c->regs[R14]|= DTRREQ;
        write_zsreg(c, R14, c->regs[R14]);     

        c->regs[R1]&= ~TxINT_ENAB;
        write_zsreg(c, R1, c->regs[R1]);
        
        /*
         *      RX DMA via W/Req
         */      

        c->regs[R1]|= WT_FN_RDYFN;
        c->regs[R1]|= WT_RDY_RT;
        c->regs[R1]|= INT_ERR_Rx;
        c->regs[R1]&= ~TxINT_ENAB;
        write_zsreg(c, R1, c->regs[R1]);
        c->regs[R1]|= WT_RDY_ENAB;
        write_zsreg(c, R1, c->regs[R1]);            
        
        /*
         *      DMA interrupts
         */
         
        /*
         *      Set up the DMA configuration
         */     
         
        dflags=claim_dma_lock();
         
        disable_dma(c->rxdma);
        clear_dma_ff(c->rxdma);
        set_dma_mode(c->rxdma, DMA_MODE_READ|0x10);
        set_dma_addr(c->rxdma, virt_to_bus(c->rx_buf[0]));
        set_dma_count(c->rxdma, c->mtu);
        enable_dma(c->rxdma);

        disable_dma(c->txdma);
        clear_dma_ff(c->txdma);
        set_dma_mode(c->txdma, DMA_MODE_WRITE);
        disable_dma(c->txdma);
        
        release_dma_lock(dflags);
        
        /*
         *      Select the DMA interrupt handlers
         */

        c->rxdma_on = 1;
        c->txdma_on = 1;
        c->tx_dma_used = 1;
         
        c->irqs = &z8530_dma_sync;
        z8530_rtsdtr(c,1);
        write_zsreg(c, R3, c->regs[R3]|RxENABLE);

        spin_unlock_irqrestore(c->lock, cflags);
        
        return 0;
}

EXPORT_SYMBOL(z8530_sync_dma_open);

/**
 *      z8530_sync_dma_close - Close down DMA I/O
 *      @dev: Network device to detach
 *      @c: Z8530 channel to move into discard mode
 *
 *      Shut down a DMA mode synchronous interface. Halt the DMA, and
 *      free the buffers.
 */
 
int z8530_sync_dma_close(struct net_device *dev, struct z8530_channel *c)
{
        u8 chk;
        unsigned long flags;
        
        c->irqs = &z8530_nop;
        c->max = 0;
        c->sync = 0;
        
        /*
         *      Disable the PC DMA channels
         */
        
        flags=claim_dma_lock(); 
        disable_dma(c->rxdma);
        clear_dma_ff(c->rxdma);
        
        c->rxdma_on = 0;
        
        disable_dma(c->txdma);
        clear_dma_ff(c->txdma);
        release_dma_lock(flags);
        
        c->txdma_on = 0;
        c->tx_dma_used = 0;

        spin_lock_irqsave(c->lock, flags);

        /*
         *      Disable DMA control mode
         */
         
        c->regs[R1]&= ~WT_RDY_ENAB;
        write_zsreg(c, R1, c->regs[R1]);            
        c->regs[R1]&= ~(WT_RDY_RT|WT_FN_RDYFN|INT_ERR_Rx);
        c->regs[R1]|= INT_ALL_Rx;
        write_zsreg(c, R1, c->regs[R1]);
        c->regs[R14]&= ~DTRREQ;
        write_zsreg(c, R14, c->regs[R14]);   
        
        if(c->rx_buf[0])
        {
                free_page((unsigned long)c->rx_buf[0]);
                c->rx_buf[0]=NULL;
        }
        if(c->tx_dma_buf[0])
        {
                free_page((unsigned  long)c->tx_dma_buf[0]);
                c->tx_dma_buf[0]=NULL;
        }
        chk=read_zsreg(c,R0);
        write_zsreg(c, R3, c->regs[R3]);
        z8530_rtsdtr(c,0);

        spin_unlock_irqrestore(c->lock, flags);

        return 0;
}

EXPORT_SYMBOL(z8530_sync_dma_close);

/**
 *      z8530_sync_txdma_open - Open a Z8530 for TX driven DMA
 *      @dev: The network device to attach
 *      @c: The Z8530 channel to configure in sync DMA mode.
 *
 *      Set up a Z85x30 device for synchronous DMA transmission. One
 *      ISA DMA channel must be available for this to work. The receive
 *      side is run in PIO mode, but then it has the bigger FIFO.
 */

int z8530_sync_txdma_open(struct net_device *dev, struct z8530_channel *c)
{
        unsigned long cflags, dflags;

        printk("Opening sync interface for TX-DMA\n");
        c->sync = 1;
        c->mtu = dev->mtu+64;
        c->count = 0;
        c->skb = NULL;
        c->skb2 = NULL;
        
        /*
         *      Allocate the DMA flip buffers. Limit by page size.
         *      Everyone runs 1500 mtu or less on wan links so this
         *      should be fine.
         */
         
        if(c->mtu  > PAGE_SIZE/2)
                return -EMSGSIZE;
         
        c->tx_dma_buf[0]=(void *)get_zeroed_page(GFP_KERNEL|GFP_DMA);
        if(c->tx_dma_buf[0]==NULL)
                return -ENOBUFS;

        c->tx_dma_buf[1] = c->tx_dma_buf[0] + PAGE_SIZE/2;


        spin_lock_irqsave(c->lock, cflags);

        /*
         *      Load the PIO receive ring
         */

        z8530_rx_done(c);
        z8530_rx_done(c);

        /*
         *      Load the DMA interfaces up
         */

        c->rxdma_on = 0;
        c->txdma_on = 0;
        
        c->tx_dma_used=0;
        c->dma_num=0;
        c->dma_ready=1;
        c->dma_tx = 1;

        /*
         *      Enable DMA control mode
         */

        /*
         *      TX DMA via DIR/REQ
         */
        c->regs[R14]|= DTRREQ;
        write_zsreg(c, R14, c->regs[R14]);     
        
        c->regs[R1]&= ~TxINT_ENAB;
        write_zsreg(c, R1, c->regs[R1]);
        
        /*
         *      Set up the DMA configuration
         */     
         
        dflags = claim_dma_lock();

        disable_dma(c->txdma);
        clear_dma_ff(c->txdma);
        set_dma_mode(c->txdma, DMA_MODE_WRITE);
        disable_dma(c->txdma);

        release_dma_lock(dflags);
        
        /*
         *      Select the DMA interrupt handlers
         */

        c->rxdma_on = 0;
        c->txdma_on = 1;
        c->tx_dma_used = 1;
         
        c->irqs = &z8530_txdma_sync;
        z8530_rtsdtr(c,1);
        write_zsreg(c, R3, c->regs[R3]|RxENABLE);
        spin_unlock_irqrestore(c->lock, cflags);
        
        return 0;
}

EXPORT_SYMBOL(z8530_sync_txdma_open);

/**
 *      z8530_sync_txdma_close - Close down a TX driven DMA channel
 *      @dev: Network device to detach
 *      @c: Z8530 channel to move into discard mode
 *
 *      Shut down a DMA/PIO split mode synchronous interface. Halt the DMA, 
 *      and  free the buffers.
 */

int z8530_sync_txdma_close(struct net_device *dev, struct z8530_channel *c)
{
        unsigned long dflags, cflags;
        u8 chk;

        
        spin_lock_irqsave(c->lock, cflags);
        
        c->irqs = &z8530_nop;
        c->max = 0;
        c->sync = 0;
        
        /*
         *      Disable the PC DMA channels
         */
         
        dflags = claim_dma_lock();

        disable_dma(c->txdma);
        clear_dma_ff(c->txdma);
        c->txdma_on = 0;
        c->tx_dma_used = 0;

        release_dma_lock(dflags);

        /*
         *      Disable DMA control mode
         */
         
        c->regs[R1]&= ~WT_RDY_ENAB;
        write_zsreg(c, R1, c->regs[R1]);            
        c->regs[R1]&= ~(WT_RDY_RT|WT_FN_RDYFN|INT_ERR_Rx);
        c->regs[R1]|= INT_ALL_Rx;
        write_zsreg(c, R1, c->regs[R1]);
        c->regs[R14]&= ~DTRREQ;
        write_zsreg(c, R14, c->regs[R14]);   
        
        if(c->tx_dma_buf[0])
        {
                free_page((unsigned long)c->tx_dma_buf[0]);
                c->tx_dma_buf[0]=NULL;
        }
        chk=read_zsreg(c,R0);
        write_zsreg(c, R3, c->regs[R3]);
        z8530_rtsdtr(c,0);

        spin_unlock_irqrestore(c->lock, cflags);
        return 0;
}


EXPORT_SYMBOL(z8530_sync_txdma_close);


/*
 *      Name strings for Z8530 chips. SGI claim to have a 130, Zilog deny
 *      it exists...
 */
 
static const char *z8530_type_name[]={
        "Z8530",
        "Z85C30",
        "Z85230"
};

/**
 *      z8530_describe - Uniformly describe a Z8530 port
 *      @dev: Z8530 device to describe
 *      @mapping: string holding mapping type (eg "I/O" or "Mem")
 *      @io: the port value in question
 *
 *      Describe a Z8530 in a standard format. We must pass the I/O as
 *      the port offset isn't predictable. The main reason for this function
 *      is to try and get a common format of report.
 */

void z8530_describe(struct z8530_dev *dev, char *mapping, unsigned long io)
{
        pr_info("%s: %s found at %s 0x%lX, IRQ %d\n",
                dev->name, 
                z8530_type_name[dev->type],
                mapping,
                Z8530_PORT_OF(io),
                dev->irq);
}

EXPORT_SYMBOL(z8530_describe);

/*
 *      Locked operation part of the z8530 init code
 */
 
static inline int do_z8530_init(struct z8530_dev *dev)
{
        /* NOP the interrupt handlers first - we might get a
           floating IRQ transition when we reset the chip */
        dev->chanA.irqs=&z8530_nop;
        dev->chanB.irqs=&z8530_nop;
        dev->chanA.dcdcheck=DCD;
        dev->chanB.dcdcheck=DCD;

        /* Reset the chip */
        write_zsreg(&dev->chanA, R9, 0xC0);
        udelay(200);
        /* Now check its valid */
        write_zsreg(&dev->chanA, R12, 0xAA);
        if(read_zsreg(&dev->chanA, R12)!=0xAA)
                return -ENODEV;
        write_zsreg(&dev->chanA, R12, 0x55);
        if(read_zsreg(&dev->chanA, R12)!=0x55)
                return -ENODEV;
                
        dev->type=Z8530;
        
        /*
         *      See the application note.
         */
         
        write_zsreg(&dev->chanA, R15, 0x01);
        
        /*
         *      If we can set the low bit of R15 then
         *      the chip is enhanced.
         */
         
        if(read_zsreg(&dev->chanA, R15)==0x01)
        {
                /* This C30 versus 230 detect is from Klaus Kudielka's dmascc */
                /* Put a char in the fifo */
                write_zsreg(&dev->chanA, R8, 0);
                if(read_zsreg(&dev->chanA, R0)&Tx_BUF_EMP)
                        dev->type = Z85230;     /* Has a FIFO */
                else
                        dev->type = Z85C30;     /* Z85C30, 1 byte FIFO */
        }
                
        /*
         *      The code assumes R7' and friends are
         *      off. Use write_zsext() for these and keep
         *      this bit clear.
         */
         
        write_zsreg(&dev->chanA, R15, 0);
                
        /*
         *      At this point it looks like the chip is behaving
         */
         
        memcpy(dev->chanA.regs, reg_init, 16);
        memcpy(dev->chanB.regs, reg_init ,16);
        
        return 0;
}

/**
 *      z8530_init - Initialise a Z8530 device
 *      @dev: Z8530 device to initialise.
 *
 *      Configure up a Z8530/Z85C30 or Z85230 chip. We check the device
 *      is present, identify the type and then program it to hopefully
 *      keep quite and behave. This matters a lot, a Z8530 in the wrong
 *      state will sometimes get into stupid modes generating 10Khz
 *      interrupt streams and the like.
 *
 *      We set the interrupt handler up to discard any events, in case
 *      we get them during reset or setp.
 *
 *      Return 0 for success, or a negative value indicating the problem
 *      in errno form.
 */

int z8530_init(struct z8530_dev *dev)
{
        unsigned long flags;
        int ret;

        /* Set up the chip level lock */
        spin_lock_init(&dev->lock);
        dev->chanA.lock = &dev->lock;
        dev->chanB.lock = &dev->lock;

        spin_lock_irqsave(&dev->lock, flags);
        ret = do_z8530_init(dev);
        spin_unlock_irqrestore(&dev->lock, flags);

        return ret;
}


EXPORT_SYMBOL(z8530_init);

/**
 *      z8530_shutdown - Shutdown a Z8530 device
 *      @dev: The Z8530 chip to shutdown
 *
 *      We set the interrupt handlers to silence any interrupts. We then 
 *      reset the chip and wait 100uS to be sure the reset completed. Just
 *      in case the caller then tries to do stuff.
 *
 *      This is called without the lock held
 */
 
int z8530_shutdown(struct z8530_dev *dev)
{
        unsigned long flags;
        /* Reset the chip */

        spin_lock_irqsave(&dev->lock, flags);
        dev->chanA.irqs=&z8530_nop;
        dev->chanB.irqs=&z8530_nop;
        write_zsreg(&dev->chanA, R9, 0xC0);
        /* We must lock the udelay, the chip is offlimits here */
        udelay(100);
        spin_unlock_irqrestore(&dev->lock, flags);
        return 0;
}

EXPORT_SYMBOL(z8530_shutdown);

/**
 *      z8530_channel_load - Load channel data
 *      @c: Z8530 channel to configure
 *      @rtable: table of register, value pairs
 *      FIXME: ioctl to allow user uploaded tables
 *
 *      Load a Z8530 channel up from the system data. We use +16 to 
 *      indicate the "prime" registers. The value 255 terminates the
 *      table.
 */

int z8530_channel_load(struct z8530_channel *c, u8 *rtable)
{
        unsigned long flags;

        spin_lock_irqsave(c->lock, flags);

        while(*rtable!=255)
        {
                int reg=*rtable++;
                if(reg>0x0F)
                        write_zsreg(c, R15, c->regs[15]|1);
                write_zsreg(c, reg&0x0F, *rtable);
                if(reg>0x0F)
                        write_zsreg(c, R15, c->regs[15]&~1);
                c->regs[reg]=*rtable++;
        }
        c->rx_function=z8530_null_rx;
        c->skb=NULL;
        c->tx_skb=NULL;
        c->tx_next_skb=NULL;
        c->mtu=1500;
        c->max=0;
        c->count=0;
        c->status=read_zsreg(c, R0);
        c->sync=1;
        write_zsreg(c, R3, c->regs[R3]|RxENABLE);

        spin_unlock_irqrestore(c->lock, flags);
        return 0;
}

EXPORT_SYMBOL(z8530_channel_load);


/**
 *      z8530_tx_begin - Begin packet transmission
 *      @c: The Z8530 channel to kick
 *
 *      This is the speed sensitive side of transmission. If we are called
 *      and no buffer is being transmitted we commence the next buffer. If
 *      nothing is queued we idle the sync. 
 *
 *      Note: We are handling this code path in the interrupt path, keep it
 *      fast or bad things will happen.
 *
 *      Called with the lock held.
 */

static void z8530_tx_begin(struct z8530_channel *c)
{
        unsigned long flags;
        if(c->tx_skb)
                return;
                
        c->tx_skb=c->tx_next_skb;
        c->tx_next_skb=NULL;
        c->tx_ptr=c->tx_next_ptr;
        
        if(c->tx_skb==NULL)
        {
                /* Idle on */
                if(c->dma_tx)
                {
                        flags=claim_dma_lock();
                        disable_dma(c->txdma);
                        /*
                         *      Check if we crapped out.
                         */
                        if (get_dma_residue(c->txdma))
                        {
                                c->netdevice->stats.tx_dropped++;
                                c->netdevice->stats.tx_fifo_errors++;
                        }
                        release_dma_lock(flags);
                }
                c->txcount=0;
        }
        else
        {
                c->txcount=c->tx_skb->len;
                
                
                if(c->dma_tx)
                {
                        /*
                         *      FIXME. DMA is broken for the original 8530,
                         *      on the older parts we need to set a flag and
                         *      wait for a further TX interrupt to fire this
                         *      stage off       
                         */
                         
                        flags=claim_dma_lock();
                        disable_dma(c->txdma);

                        /*
                         *      These two are needed by the 8530/85C30
                         *      and must be issued when idling.
                         */
                         
                        if(c->dev->type!=Z85230)
                        {
                                write_zsctrl(c, RES_Tx_CRC);
                                write_zsctrl(c, RES_EOM_L);
                        }       
                        write_zsreg(c, R10, c->regs[10]&~ABUNDER);
                        clear_dma_ff(c->txdma);
                        set_dma_addr(c->txdma, virt_to_bus(c->tx_ptr));
                        set_dma_count(c->txdma, c->txcount);
                        enable_dma(c->txdma);
                        release_dma_lock(flags);
                        write_zsctrl(c, RES_EOM_L);
                        write_zsreg(c, R5, c->regs[R5]|TxENAB);
                }
                else
                {

                        /* ABUNDER off */
                        write_zsreg(c, R10, c->regs[10]);
                        write_zsctrl(c, RES_Tx_CRC);
        
                        while(c->txcount && (read_zsreg(c,R0)&Tx_BUF_EMP))
                        {               
                                write_zsreg(c, R8, *c->tx_ptr++);
                                c->txcount--;
                        }

                }
        }
        /*
         *      Since we emptied tx_skb we can ask for more
         */
        netif_wake_queue(c->netdevice);
}

/**
 *      z8530_tx_done - TX complete callback
 *      @c: The channel that completed a transmit.
 *
 *      This is called when we complete a packet send. We wake the queue,
 *      start the next packet going and then free the buffer of the existing
 *      packet. This code is fairly timing sensitive.
 *
 *      Called with the register lock held.
 */

static void z8530_tx_done(struct z8530_channel *c)
{
        struct sk_buff *skb;

        /* Actually this can happen.*/
        if (c->tx_skb == NULL)
                return;

        skb = c->tx_skb;
        c->tx_skb = NULL;
        z8530_tx_begin(c);
        c->netdevice->stats.tx_packets++;
        c->netdevice->stats.tx_bytes += skb->len;
        dev_consume_skb_irq(skb);
}

/**
 *      z8530_null_rx - Discard a packet
 *      @c: The channel the packet arrived on
 *      @skb: The buffer
 *
 *      We point the receive handler at this function when idle. Instead
 *      of processing the frames we get to throw them away.
 */
 
void z8530_null_rx(struct z8530_channel *c, struct sk_buff *skb)
{
        dev_kfree_skb_any(skb);
}

EXPORT_SYMBOL(z8530_null_rx);

/**
 *      z8530_rx_done - Receive completion callback
 *      @c: The channel that completed a receive
 *
 *      A new packet is complete. Our goal here is to get back into receive
 *      mode as fast as possible. On the Z85230 we could change to using
 *      ESCC mode, but on the older chips we have no choice. We flip to the
 *      new buffer immediately in DMA mode so that the DMA of the next
 *      frame can occur while we are copying the previous buffer to an sk_buff
 *
 *      Called with the lock held
 */
 
static void z8530_rx_done(struct z8530_channel *c)
{
        struct sk_buff *skb;
        int ct;
        
        /*
         *      Is our receive engine in DMA mode
         */
         
        if(c->rxdma_on)
        {
                /*
                 *      Save the ready state and the buffer currently
                 *      being used as the DMA target
                 */
                 
                int ready=c->dma_ready;
                unsigned char *rxb=c->rx_buf[c->dma_num];
                unsigned long flags;
                
                /*
                 *      Complete this DMA. Necessary to find the length
                 */             
                 
                flags=claim_dma_lock();
                
                disable_dma(c->rxdma);
                clear_dma_ff(c->rxdma);
                c->rxdma_on=0;
                ct=c->mtu-get_dma_residue(c->rxdma);
                if(ct<0)
                        ct=2;   /* Shit happens.. */
                c->dma_ready=0;
                
                /*
                 *      Normal case: the other slot is free, start the next DMA
                 *      into it immediately.
                 */
                 
                if(ready)
                {
                        c->dma_num^=1;
                        set_dma_mode(c->rxdma, DMA_MODE_READ|0x10);
                        set_dma_addr(c->rxdma, virt_to_bus(c->rx_buf[c->dma_num]));
                        set_dma_count(c->rxdma, c->mtu);
                        c->rxdma_on = 1;
                        enable_dma(c->rxdma);
                        /* Stop any frames that we missed the head of 
                           from passing */
                        write_zsreg(c, R0, RES_Rx_CRC);
                }
                else
                        /* Can't occur as we dont reenable the DMA irq until
                           after the flip is done */
                        netdev_warn(c->netdevice, "DMA flip overrun!\n");

                release_dma_lock(flags);

                /*
                 *      Shove the old buffer into an sk_buff. We can't DMA
                 *      directly into one on a PC - it might be above the 16Mb
                 *      boundary. Optimisation - we could check to see if we
                 *      can avoid the copy. Optimisation 2 - make the memcpy
                 *      a copychecksum.
                 */

                skb = dev_alloc_skb(ct);
                if (skb == NULL) {
                        c->netdevice->stats.rx_dropped++;
                        netdev_warn(c->netdevice, "Memory squeeze\n");
                } else {
                        skb_put(skb, ct);
                        skb_copy_to_linear_data(skb, rxb, ct);
                        c->netdevice->stats.rx_packets++;
                        c->netdevice->stats.rx_bytes += ct;
                }
                c->dma_ready = 1;
        } else {
                RT_LOCK;
                skb = c->skb;

                /*
                 *      The game we play for non DMA is similar. We want to
                 *      get the controller set up for the next packet as fast
                 *      as possible. We potentially only have one byte + the
                 *      fifo length for this. Thus we want to flip to the new
                 *      buffer and then mess around copying and allocating
                 *      things. For the current case it doesn't matter but
                 *      if you build a system where the sync irq isn't blocked
                 *      by the kernel IRQ disable then you need only block the
                 *      sync IRQ for the RT_LOCK area.
                 *
                 */
                ct=c->count;

                c->skb = c->skb2;
                c->count = 0;
                c->max = c->mtu;
                if (c->skb) {
                        c->dptr = c->skb->data;
                        c->max = c->mtu;
                } else {
                        c->count = 0;
                        c->max = 0;
                }
                RT_UNLOCK;

                c->skb2 = dev_alloc_skb(c->mtu);
                if (c->skb2 == NULL)
                        netdev_warn(c->netdevice, "memory squeeze\n");
                else
                        skb_put(c->skb2, c->mtu);
                c->netdevice->stats.rx_packets++;
                c->netdevice->stats.rx_bytes += ct;
        }
        /*
         *      If we received a frame we must now process it.
         */
        if (skb) {
                skb_trim(skb, ct);
                c->rx_function(c, skb);
        } else {
                c->netdevice->stats.rx_dropped++;
                netdev_err(c->netdevice, "Lost a frame\n");
        }
}

/**
 *      spans_boundary - Check a packet can be ISA DMA'd
 *      @skb: The buffer to check
 *
 *      Returns true if the buffer cross a DMA boundary on a PC. The poor
 *      thing can only DMA within a 64K block not across the edges of it.
 */

static inline int spans_boundary(struct sk_buff *skb)
{
        unsigned long a=(unsigned long)skb->data;
        a^=(a+skb->len);
        if(a&0x00010000)        /* If the 64K bit is different.. */
                return 1;
        return 0;
}

/**
 *      z8530_queue_xmit - Queue a packet
 *      @c: The channel to use
 *      @skb: The packet to kick down the channel
 *
 *      Queue a packet for transmission. Because we have rather
 *      hard to hit interrupt latencies for the Z85230 per packet 
 *      even in DMA mode we do the flip to DMA buffer if needed here
 *      not in the IRQ.
 *
 *      Called from the network code. The lock is not held at this 
 *      point.
 */

netdev_tx_t z8530_queue_xmit(struct z8530_channel *c, struct sk_buff *skb)
{
        unsigned long flags;
        
        netif_stop_queue(c->netdevice);
        if(c->tx_next_skb)
                return NETDEV_TX_BUSY;

        
        /* PC SPECIFIC - DMA limits */
        
        /*
         *      If we will DMA the transmit and its gone over the ISA bus
         *      limit, then copy to the flip buffer
         */
         
        if(c->dma_tx && ((unsigned long)(virt_to_bus(skb->data+skb->len))>=16*1024*1024 || spans_boundary(skb)))
        {
                /* 
                 *      Send the flip buffer, and flip the flippy bit.
                 *      We don't care which is used when just so long as
                 *      we never use the same buffer twice in a row. Since
                 *      only one buffer can be going out at a time the other
                 *      has to be safe.
                 */
                c->tx_next_ptr=c->tx_dma_buf[c->tx_dma_used];
                c->tx_dma_used^=1;      /* Flip temp buffer */
                skb_copy_from_linear_data(skb, c->tx_next_ptr, skb->len);
        }
        else
                c->tx_next_ptr=skb->data;       
        RT_LOCK;
        c->tx_next_skb=skb;
        RT_UNLOCK;
        
        spin_lock_irqsave(c->lock, flags);
        z8530_tx_begin(c);
        spin_unlock_irqrestore(c->lock, flags);
        
        return NETDEV_TX_OK;
}

EXPORT_SYMBOL(z8530_queue_xmit);

/*
 *      Module support
 */
static const char banner[] __initconst =
        KERN_INFO "Generic Z85C30/Z85230 interface driver v0.02\n";

static int __init z85230_init_driver(void)
{
        printk(banner);
        return 0;
}
module_init(z85230_init_driver);

static void __exit z85230_cleanup_driver(void)
{
}
module_exit(z85230_cleanup_driver);

MODULE_AUTHOR("Red Hat Inc.");
MODULE_DESCRIPTION("Z85x30 synchronous driver core");
MODULE_LICENSE("GPL");