/*
 * Standalone EHCI usb debug driver
 *
 * Originally written by:
 *  Eric W. Biederman" <ebiederm@xmission.com> and
 *  Yinghai Lu <yhlu.kernel@gmail.com>
 *
 * Changes for early/late printk and HW errata:
 *  Jason Wessel <jason.wessel@windriver.com>
 *  Copyright (C) 2009 Wind River Systems, Inc.
 *
 */

#include <linux/console.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/pci_regs.h>
#include <linux/pci_ids.h>
#include <linux/usb/ch9.h>
#include <linux/usb/ehci_def.h>
#include <linux/delay.h>
#include <linux/serial_core.h>
#include <linux/kgdb.h>
#include <linux/kthread.h>
#include <asm/io.h>
#include <asm/pci-direct.h>
#include <asm/fixmap.h>

/* The code here is intended to talk directly to the EHCI debug port
 * and does not require that you have any kind of USB host controller
 * drivers or USB device drivers compiled into the kernel.
 *
 * If you make a change to anything in here, the following test cases
 * need to pass where a USB debug device works in the following
 * configurations.
 *
 * 1. boot args:  earlyprintk=dbgp
 *     o kernel compiled with # CONFIG_USB_EHCI_HCD is not set
 *     o kernel compiled with CONFIG_USB_EHCI_HCD=y
 * 2. boot args: earlyprintk=dbgp,keep
 *     o kernel compiled with # CONFIG_USB_EHCI_HCD is not set
 *     o kernel compiled with CONFIG_USB_EHCI_HCD=y
 * 3. boot args: earlyprintk=dbgp console=ttyUSB0
 *     o kernel has CONFIG_USB_EHCI_HCD=y and
 *       CONFIG_USB_SERIAL_DEBUG=y
 * 4. boot args: earlyprintk=vga,dbgp
 *     o kernel compiled with # CONFIG_USB_EHCI_HCD is not set
 *     o kernel compiled with CONFIG_USB_EHCI_HCD=y
 *
 * For the 4th configuration you can turn on or off the DBGP_DEBUG
 * such that you can debug the dbgp device's driver code.
 */

static int dbgp_phys_port = 1;

static struct ehci_caps __iomem *ehci_caps;
static struct ehci_regs __iomem *ehci_regs;
static struct ehci_dbg_port __iomem *ehci_debug;
static int dbgp_not_safe; /* Cannot use debug device during ehci reset */
static unsigned int dbgp_endpoint_out;
static unsigned int dbgp_endpoint_in;

struct ehci_dev {
        u32 bus;
        u32 slot;
        u32 func;
};

static struct ehci_dev ehci_dev;

#define USB_DEBUG_DEVNUM 127

#ifdef DBGP_DEBUG
#define dbgp_printk printk
static void dbgp_ehci_status(char *str)
{
        if (!ehci_debug)
                return;
        dbgp_printk("dbgp: %s\n", str);
        dbgp_printk("  Debug control: %08x", readl(&ehci_debug->control));
        dbgp_printk("  ehci cmd     : %08x", readl(&ehci_regs->command));
        dbgp_printk("  ehci conf flg: %08x\n",
                    readl(&ehci_regs->configured_flag));
        dbgp_printk("  ehci status  : %08x", readl(&ehci_regs->status));
        dbgp_printk("  ehci portsc  : %08x\n",
                    readl(&ehci_regs->port_status[dbgp_phys_port - 1]));
}
#else
static inline void dbgp_ehci_status(char *str) { }
static inline void dbgp_printk(const char *fmt, ...) { }
#endif

static inline u32 dbgp_len_update(u32 x, u32 len)
{
        return (x & ~0x0f) | (len & 0x0f);
}

#ifdef CONFIG_KGDB
static struct kgdb_io kgdbdbgp_io_ops;
#define dbgp_kgdb_mode (dbg_io_ops == &kgdbdbgp_io_ops)
#else
#define dbgp_kgdb_mode (0)
#endif

/* Local version of HC_LENGTH macro as ehci struct is not available here */
#define EARLY_HC_LENGTH(p)      (0x00ff & (p)) /* bits 7 : 0 */

/*
 * USB Packet IDs (PIDs)
 */

/* token */
#define USB_PID_OUT             0xe1
#define USB_PID_IN              0x69
#define USB_PID_SOF             0xa5
#define USB_PID_SETUP           0x2d
/* handshake */
#define USB_PID_ACK             0xd2
#define USB_PID_NAK             0x5a
#define USB_PID_STALL           0x1e
#define USB_PID_NYET            0x96
/* data */
#define USB_PID_DATA0           0xc3
#define USB_PID_DATA1           0x4b
#define USB_PID_DATA2           0x87
#define USB_PID_MDATA           0x0f
/* Special */
#define USB_PID_PREAMBLE        0x3c
#define USB_PID_ERR             0x3c
#define USB_PID_SPLIT           0x78
#define USB_PID_PING            0xb4
#define USB_PID_UNDEF_0         0xf0

#define USB_PID_DATA_TOGGLE     0x88
#define DBGP_CLAIM (DBGP_OWNER | DBGP_ENABLED | DBGP_INUSE)

#define PCI_CAP_ID_EHCI_DEBUG   0xa

#define HUB_ROOT_RESET_TIME     50      /* times are in msec */
#define HUB_SHORT_RESET_TIME    10
#define HUB_LONG_RESET_TIME     200
#define HUB_RESET_TIMEOUT       500

#define DBGP_MAX_PACKET         8
#define DBGP_TIMEOUT            (250 * 1000)
#define DBGP_LOOPS              1000

static inline u32 dbgp_pid_write_update(u32 x, u32 tok)
{
        static int data0 = USB_PID_DATA1;
        data0 ^= USB_PID_DATA_TOGGLE;
        return (x & 0xffff0000) | (data0 << 8) | (tok & 0xff);
}

static inline u32 dbgp_pid_read_update(u32 x, u32 tok)
{
        return (x & 0xffff0000) | (USB_PID_DATA0 << 8) | (tok & 0xff);
}

static int dbgp_wait_until_complete(void)
{
        u32 ctrl;
        int loop = DBGP_TIMEOUT;

        do {
                ctrl = readl(&ehci_debug->control);
                /* Stop when the transaction is finished */
                if (ctrl & DBGP_DONE)
                        break;
                udelay(1);
        } while (--loop > 0);

        if (!loop)
                return -DBGP_TIMEOUT;

        /*
         * Now that we have observed the completed transaction,
         * clear the done bit.
         */
        writel(ctrl | DBGP_DONE, &ehci_debug->control);
        return (ctrl & DBGP_ERROR) ? -DBGP_ERRCODE(ctrl) : DBGP_LEN(ctrl);
}

static inline void dbgp_mdelay(int ms)
{
        int i;

        while (ms--) {
                for (i = 0; i < 1000; i++)
                        outb(0x1, 0x80);
        }
}

static void dbgp_breath(void)
{
        /* Sleep to give the debug port a chance to breathe */
}

static int dbgp_wait_until_done(unsigned ctrl, int loop)
{
        u32 pids, lpid;
        int ret;

retry:
        writel(ctrl | DBGP_GO, &ehci_debug->control);
        ret = dbgp_wait_until_complete();
        pids = readl(&ehci_debug->pids);
        lpid = DBGP_PID_GET(pids);

        if (ret < 0) {
                /* A -DBGP_TIMEOUT failure here means the device has
                 * failed, perhaps because it was unplugged, in which
                 * case we do not want to hang the system so the dbgp
                 * will be marked as unsafe to use.  EHCI reset is the
                 * only way to recover if you unplug the dbgp device.
                 */
                if (ret == -DBGP_TIMEOUT && !dbgp_not_safe)
                        dbgp_not_safe = 1;
                if (ret == -DBGP_ERR_BAD && --loop > 0)
                        goto retry;
                return ret;
        }

        /*
         * If the port is getting full or it has dropped data
         * start pacing ourselves, not necessary but it's friendly.
         */
        if ((lpid == USB_PID_NAK) || (lpid == USB_PID_NYET))
                dbgp_breath();

        /* If I get a NACK reissue the transmission */
        if (lpid == USB_PID_NAK) {
                if (--loop > 0)
                        goto retry;
        }

        return ret;
}

static inline void dbgp_set_data(const void *buf, int size)
{
        const unsigned char *bytes = buf;
        u32 lo, hi;
        int i;

        lo = hi = 0;
        for (i = 0; i < 4 && i < size; i++)
                lo |= bytes[i] << (8*i);
        for (; i < 8 && i < size; i++)
                hi |= bytes[i] << (8*(i - 4));
        writel(lo, &ehci_debug->data03);
        writel(hi, &ehci_debug->data47);
}

static inline void dbgp_get_data(void *buf, int size)
{
        unsigned char *bytes = buf;
        u32 lo, hi;
        int i;

        lo = readl(&ehci_debug->data03);
        hi = readl(&ehci_debug->data47);
        for (i = 0; i < 4 && i < size; i++)
                bytes[i] = (lo >> (8*i)) & 0xff;
        for (; i < 8 && i < size; i++)
                bytes[i] = (hi >> (8*(i - 4))) & 0xff;
}

static int dbgp_bulk_write(unsigned devnum, unsigned endpoint,
                         const char *bytes, int size)
{
        int ret;
        u32 addr;
        u32 pids, ctrl;

        if (size > DBGP_MAX_PACKET)
                return -1;

        addr = DBGP_EPADDR(devnum, endpoint);

        pids = readl(&ehci_debug->pids);
        pids = dbgp_pid_write_update(pids, USB_PID_OUT);

        ctrl = readl(&ehci_debug->control);
        ctrl = dbgp_len_update(ctrl, size);
        ctrl |= DBGP_OUT;
        ctrl |= DBGP_GO;

        dbgp_set_data(bytes, size);
        writel(addr, &ehci_debug->address);
        writel(pids, &ehci_debug->pids);
        ret = dbgp_wait_until_done(ctrl, DBGP_LOOPS);

        return ret;
}

static int dbgp_bulk_read(unsigned devnum, unsigned endpoint, void *data,
                          int size, int loops)
{
        u32 pids, addr, ctrl;
        int ret;

        if (size > DBGP_MAX_PACKET)
                return -1;

        addr = DBGP_EPADDR(devnum, endpoint);

        pids = readl(&ehci_debug->pids);
        pids = dbgp_pid_read_update(pids, USB_PID_IN);

        ctrl = readl(&ehci_debug->control);
        ctrl = dbgp_len_update(ctrl, size);
        ctrl &= ~DBGP_OUT;
        ctrl |= DBGP_GO;

        writel(addr, &ehci_debug->address);
        writel(pids, &ehci_debug->pids);
        ret = dbgp_wait_until_done(ctrl, loops);
        if (ret < 0)
                return ret;

        if (size > ret)
                size = ret;
        dbgp_get_data(data, size);
        return ret;
}

static int dbgp_control_msg(unsigned devnum, int requesttype,
        int request, int value, int index, void *data, int size)
{
        u32 pids, addr, ctrl;
        struct usb_ctrlrequest req;
        int read;
        int ret;

        read = (requesttype & USB_DIR_IN) != 0;
        if (size > (read ? DBGP_MAX_PACKET : 0))
                return -1;

        /* Compute the control message */
        req.bRequestType = requesttype;
        req.bRequest = request;
        req.wValue = cpu_to_le16(value);
        req.wIndex = cpu_to_le16(index);
        req.wLength = cpu_to_le16(size);

        pids = DBGP_PID_SET(USB_PID_DATA0, USB_PID_SETUP);
        addr = DBGP_EPADDR(devnum, 0);

        ctrl = readl(&ehci_debug->control);
        ctrl = dbgp_len_update(ctrl, sizeof(req));
        ctrl |= DBGP_OUT;
        ctrl |= DBGP_GO;

        /* Send the setup message */
        dbgp_set_data(&req, sizeof(req));
        writel(addr, &ehci_debug->address);
        writel(pids, &ehci_debug->pids);
        ret = dbgp_wait_until_done(ctrl, DBGP_LOOPS);
        if (ret < 0)
                return ret;

        /* Read the result */
        return dbgp_bulk_read(devnum, 0, data, size, DBGP_LOOPS);
}

/* Find a PCI capability */
static u32 __init find_cap(u32 num, u32 slot, u32 func, int cap)
{
        u8 pos;
        int bytes;

        if (!(read_pci_config_16(num, slot, func, PCI_STATUS) &
                PCI_STATUS_CAP_LIST))
                return 0;

        pos = read_pci_config_byte(num, slot, func, PCI_CAPABILITY_LIST);
        for (bytes = 0; bytes < 48 && pos >= 0x40; bytes++) {
                u8 id;

                pos &= ~3;
                id = read_pci_config_byte(num, slot, func, pos+PCI_CAP_LIST_ID);
                if (id == 0xff)
                        break;
                if (id == cap)
                        return pos;

                pos = read_pci_config_byte(num, slot, func,
                                                 pos+PCI_CAP_LIST_NEXT);
        }
        return 0;
}

static u32 __init __find_dbgp(u32 bus, u32 slot, u32 func)
{
        u32 class;

        class = read_pci_config(bus, slot, func, PCI_CLASS_REVISION);
        if ((class >> 8) != PCI_CLASS_SERIAL_USB_EHCI)
                return 0;

        return find_cap(bus, slot, func, PCI_CAP_ID_EHCI_DEBUG);
}

static u32 __init find_dbgp(int ehci_num, u32 *rbus, u32 *rslot, u32 *rfunc)
{
        u32 bus, slot, func;

        for (bus = 0; bus < 256; bus++) {
                for (slot = 0; slot < 32; slot++) {
                        for (func = 0; func < 8; func++) {
                                unsigned cap;

                                cap = __find_dbgp(bus, slot, func);

                                if (!cap)
                                        continue;
                                if (ehci_num-- != 0)
                                        continue;
                                *rbus = bus;
                                *rslot = slot;
                                *rfunc = func;
                                return cap;
                        }
                }
        }
        return 0;
}

static int dbgp_ehci_startup(void)
{
        u32 ctrl, cmd, status;
        int loop;

        /* Claim ownership, but do not enable yet */
        ctrl = readl(&ehci_debug->control);
        ctrl |= DBGP_OWNER;
        ctrl &= ~(DBGP_ENABLED | DBGP_INUSE);
        writel(ctrl, &ehci_debug->control);
        udelay(1);

        dbgp_ehci_status("EHCI startup");
        /* Start the ehci running */
        cmd = readl(&ehci_regs->command);
        cmd &= ~(CMD_LRESET | CMD_IAAD | CMD_PSE | CMD_ASE | CMD_RESET);
        cmd |= CMD_RUN;
        writel(cmd, &ehci_regs->command);

        /* Ensure everything is routed to the EHCI */
        writel(FLAG_CF, &ehci_regs->configured_flag);

        /* Wait until the controller is no longer halted */
        loop = 1000;
        do {
                status = readl(&ehci_regs->status);
                if (!(status & STS_HALT))
                        break;
                udelay(1);
        } while (--loop > 0);

        if (!loop) {
                dbgp_printk("ehci can not be started\n");
                return -ENODEV;
        }
        dbgp_printk("ehci started\n");
        return 0;
}

static int dbgp_ehci_controller_reset(void)
{
        int loop = 250 * 1000;
        u32 cmd;

        /* Reset the EHCI controller */
        cmd = readl(&ehci_regs->command);
        cmd |= CMD_RESET;
        writel(cmd, &ehci_regs->command);
        do {
                cmd = readl(&ehci_regs->command);
        } while ((cmd & CMD_RESET) && (--loop > 0));

        if (!loop) {
                dbgp_printk("can not reset ehci\n");
                return -1;
        }
        dbgp_ehci_status("ehci reset done");
        return 0;
}
static int ehci_wait_for_port(int port);
/* Return 0 on success
 * Return -ENODEV for any general failure
 * Return -EIO if wait for port fails
 */
static int _dbgp_external_startup(void)
{
        int devnum;
        struct usb_debug_descriptor dbgp_desc;
        int ret;
        u32 ctrl, portsc, cmd;
        int dbg_port = dbgp_phys_port;
        int tries = 3;
        int reset_port_tries = 1;
        int try_hard_once = 1;

try_port_reset_again:
        ret = dbgp_ehci_startup();
        if (ret)
                return ret;

        /* Wait for a device to show up in the debug port */
        ret = ehci_wait_for_port(dbg_port);
        if (ret < 0) {
                portsc = readl(&ehci_regs->port_status[dbg_port - 1]);
                if (!(portsc & PORT_CONNECT) && try_hard_once) {
                        /* Last ditch effort to try to force enable
                         * the debug device by using the packet test
                         * ehci command to try and wake it up. */
                        try_hard_once = 0;
                        cmd = readl(&ehci_regs->command);
                        cmd &= ~CMD_RUN;
                        writel(cmd, &ehci_regs->command);
                        portsc = readl(&ehci_regs->port_status[dbg_port - 1]);
                        portsc |= PORT_TEST_PKT;
                        writel(portsc, &ehci_regs->port_status[dbg_port - 1]);
                        dbgp_ehci_status("Trying to force debug port online");
                        mdelay(50);
                        dbgp_ehci_controller_reset();
                        goto try_port_reset_again;
                } else if (reset_port_tries--) {
                        goto try_port_reset_again;
                }
                dbgp_printk("No device found in debug port\n");
                return -EIO;
        }
        dbgp_ehci_status("wait for port done");

        /* Enable the debug port */
        ctrl = readl(&ehci_debug->control);
        ctrl |= DBGP_CLAIM;
        writel(ctrl, &ehci_debug->control);
        ctrl = readl(&ehci_debug->control);
        if ((ctrl & DBGP_CLAIM) != DBGP_CLAIM) {
                dbgp_printk("No device in debug port\n");
                writel(ctrl & ~DBGP_CLAIM, &ehci_debug->control);
                return -ENODEV;
        }
        dbgp_ehci_status("debug ported enabled");

        /* Completely transfer the debug device to the debug controller */
        portsc = readl(&ehci_regs->port_status[dbg_port - 1]);
        portsc &= ~PORT_PE;
        writel(portsc, &ehci_regs->port_status[dbg_port - 1]);

        dbgp_mdelay(100);

try_again:
        /* Find the debug device and make it device number 127 */
        for (devnum = 0; devnum <= 127; devnum++) {
                ret = dbgp_control_msg(devnum,
                        USB_DIR_IN | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
                        USB_REQ_GET_DESCRIPTOR, (USB_DT_DEBUG << 8), 0,
                        &dbgp_desc, sizeof(dbgp_desc));
                if (ret > 0)
                        break;
        }
        if (devnum > 127) {
                dbgp_printk("Could not find attached debug device\n");
                goto err;
        }
        dbgp_endpoint_out = dbgp_desc.bDebugOutEndpoint;
        dbgp_endpoint_in = dbgp_desc.bDebugInEndpoint;

        /* Move the device to 127 if it isn't already there */
        if (devnum != USB_DEBUG_DEVNUM) {
                ret = dbgp_control_msg(devnum,
                        USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
                        USB_REQ_SET_ADDRESS, USB_DEBUG_DEVNUM, 0, NULL, 0);
                if (ret < 0) {
                        dbgp_printk("Could not move attached device to %d\n",
                                USB_DEBUG_DEVNUM);
                        goto err;
                }
                devnum = USB_DEBUG_DEVNUM;
                dbgp_printk("debug device renamed to 127\n");
        }

        /* Enable the debug interface */
        ret = dbgp_control_msg(USB_DEBUG_DEVNUM,
                USB_DIR_OUT | USB_TYPE_STANDARD | USB_RECIP_DEVICE,
                USB_REQ_SET_FEATURE, USB_DEVICE_DEBUG_MODE, 0, NULL, 0);
        if (ret < 0) {
                dbgp_printk(" Could not enable the debug device\n");
                goto err;
        }
        dbgp_printk("debug interface enabled\n");
        /* Perform a small write to get the even/odd data state in sync
         */
        ret = dbgp_bulk_write(USB_DEBUG_DEVNUM, dbgp_endpoint_out, " ", 1);
        if (ret < 0) {
                dbgp_printk("dbgp_bulk_write failed: %d\n", ret);
                goto err;
        }
        dbgp_printk("small write done\n");
        dbgp_not_safe = 0;

        return 0;
err:
        if (tries--)
                goto try_again;
        return -ENODEV;
}

static int ehci_reset_port(int port)
{
        u32 portsc;
        u32 delay_time, delay;
        int loop;

        dbgp_ehci_status("reset port");
        /* Reset the usb debug port */
        portsc = readl(&ehci_regs->port_status[port - 1]);
        portsc &= ~PORT_PE;
        portsc |= PORT_RESET;
        writel(portsc, &ehci_regs->port_status[port - 1]);

        delay = HUB_ROOT_RESET_TIME;
        for (delay_time = 0; delay_time < HUB_RESET_TIMEOUT;
             delay_time += delay) {
                dbgp_mdelay(delay);
                portsc = readl(&ehci_regs->port_status[port - 1]);
                if (!(portsc & PORT_RESET))
                        break;
        }
                if (portsc & PORT_RESET) {
                        /* force reset to complete */
                        loop = 100 * 1000;
                        writel(portsc & ~(PORT_RWC_BITS | PORT_RESET),
                                &ehci_regs->port_status[port - 1]);
                        do {
                                udelay(1);
                                portsc = readl(&ehci_regs->port_status[port-1]);
                        } while ((portsc & PORT_RESET) && (--loop > 0));
                }

                /* Device went away? */
                if (!(portsc & PORT_CONNECT))
                        return -ENOTCONN;

                /* bomb out completely if something weird happened */
                if ((portsc & PORT_CSC))
                        return -EINVAL;

                /* If we've finished resetting, then break out of the loop */
                if (!(portsc & PORT_RESET) && (portsc & PORT_PE))
                        return 0;
        return -EBUSY;
}

static int ehci_wait_for_port(int port)
{
        u32 status;
        int ret, reps;

        for (reps = 0; reps < 300; reps++) {
                status = readl(&ehci_regs->status);
                if (status & STS_PCD)
                        break;
                dbgp_mdelay(1);
        }
        ret = ehci_reset_port(port);
        if (ret == 0)
                return 0;
        return -ENOTCONN;
}

typedef void (*set_debug_port_t)(int port);

static void __init default_set_debug_port(int port)
{
}

static set_debug_port_t __initdata set_debug_port = default_set_debug_port;

static void __init nvidia_set_debug_port(int port)
{
        u32 dword;
        dword = read_pci_config(ehci_dev.bus, ehci_dev.slot, ehci_dev.func,
                                 0x74);
        dword &= ~(0x0f<<12);
        dword |= ((port & 0x0f)<<12);
        write_pci_config(ehci_dev.bus, ehci_dev.slot, ehci_dev.func, 0x74,
                                 dword);
        dbgp_printk("set debug port to %d\n", port);
}

static void __init detect_set_debug_port(void)
{
        u32 vendorid;

        vendorid = read_pci_config(ehci_dev.bus, ehci_dev.slot, ehci_dev.func,
                 0x00);

        if ((vendorid & 0xffff) == 0x10de) {
                dbgp_printk("using nvidia set_debug_port\n");
                set_debug_port = nvidia_set_debug_port;
        }
}

/* The code in early_ehci_bios_handoff() is derived from the usb pci
 * quirk initialization, but altered so as to use the early PCI
 * routines. */
#define EHCI_USBLEGSUP_BIOS     (1 << 16)       /* BIOS semaphore */
#define EHCI_USBLEGCTLSTS       4               /* legacy control/status */
static void __init early_ehci_bios_handoff(void)
{
        u32 hcc_params = readl(&ehci_caps->hcc_params);
        int offset = (hcc_params >> 8) & 0xff;
        u32 cap;
        int msec;

        if (!offset)
                return;

        cap = read_pci_config(ehci_dev.bus, ehci_dev.slot,
                              ehci_dev.func, offset);
        dbgp_printk("dbgp: ehci BIOS state %08x\n", cap);

        if ((cap & 0xff) == 1 && (cap & EHCI_USBLEGSUP_BIOS)) {
                dbgp_printk("dbgp: BIOS handoff\n");
                write_pci_config_byte(ehci_dev.bus, ehci_dev.slot,
                                      ehci_dev.func, offset + 3, 1);
        }

        /* if boot firmware now owns EHCI, spin till it hands it over. */
        msec = 1000;
        while ((cap & EHCI_USBLEGSUP_BIOS) && (msec > 0)) {
                mdelay(10);
                msec -= 10;
                cap = read_pci_config(ehci_dev.bus, ehci_dev.slot,
                                      ehci_dev.func, offset);
        }

        if (cap & EHCI_USBLEGSUP_BIOS) {
                /* well, possibly buggy BIOS... try to shut it down,
                 * and hope nothing goes too wrong */
                dbgp_printk("dbgp: BIOS handoff failed: %08x\n", cap);
                write_pci_config_byte(ehci_dev.bus, ehci_dev.slot,
                                      ehci_dev.func, offset + 2, 0);
        }

        /* just in case, always disable EHCI SMIs */
        write_pci_config_byte(ehci_dev.bus, ehci_dev.slot, ehci_dev.func,
                              offset + EHCI_USBLEGCTLSTS, 0);
}

static int __init ehci_setup(void)
{
        u32 ctrl, portsc, hcs_params;
        u32 debug_port, new_debug_port = 0, n_ports;
        int ret, i;
        int port_map_tried;
        int playtimes = 3;

        early_ehci_bios_handoff();

try_next_time:
        port_map_tried = 0;

try_next_port:

        hcs_params = readl(&ehci_caps->hcs_params);
        debug_port = HCS_DEBUG_PORT(hcs_params);
        dbgp_phys_port = debug_port;
        n_ports    = HCS_N_PORTS(hcs_params);

        dbgp_printk("debug_port: %d\n", debug_port);
        dbgp_printk("n_ports:    %d\n", n_ports);
        dbgp_ehci_status("");

        for (i = 1; i <= n_ports; i++) {
                portsc = readl(&ehci_regs->port_status[i-1]);
                dbgp_printk("portstatus%d: %08x\n", i, portsc);
        }

        if (port_map_tried && (new_debug_port != debug_port)) {
                if (--playtimes) {
                        set_debug_port(new_debug_port);
                        goto try_next_time;
                }
                return -1;
        }

        /* Only reset the controller if it is not already in the
         * configured state */
        if (!(readl(&ehci_regs->configured_flag) & FLAG_CF)) {
                if (dbgp_ehci_controller_reset() != 0)
                        return -1;
        } else {
                dbgp_ehci_status("ehci skip - already configured");
        }

        ret = _dbgp_external_startup();
        if (ret == -EIO)
                goto next_debug_port;

        if (ret < 0) {
                /* Things didn't work so remove my claim */
                ctrl = readl(&ehci_debug->control);
                ctrl &= ~(DBGP_CLAIM | DBGP_OUT);
                writel(ctrl, &ehci_debug->control);
                return -1;
        }
        return 0;

next_debug_port:
        port_map_tried |= (1<<(debug_port - 1));
        new_debug_port = ((debug_port-1+1)%n_ports) + 1;
        if (port_map_tried != ((1<<n_ports) - 1)) {
                set_debug_port(new_debug_port);
                goto try_next_port;
        }
        if (--playtimes) {
                set_debug_port(new_debug_port);
                goto try_next_time;
        }

        return -1;
}

int __init early_dbgp_init(char *s)
{
        u32 debug_port, bar, offset;
        u32 bus, slot, func, cap;
        void __iomem *ehci_bar;
        u32 dbgp_num;
        u32 bar_val;
        char *e;
        int ret;
        u8 byte;

        if (!early_pci_allowed())
                return -1;

        dbgp_num = 0;
        if (*s)
                dbgp_num = simple_strtoul(s, &e, 10);
        dbgp_printk("dbgp_num: %d\n", dbgp_num);

        cap = find_dbgp(dbgp_num, &bus, &slot, &func);
        if (!cap)
                return -1;

        dbgp_printk("Found EHCI debug port on %02x:%02x.%1x\n", bus, slot,
                         func);

        debug_port = read_pci_config(bus, slot, func, cap);
        bar = (debug_port >> 29) & 0x7;
        bar = (bar * 4) + 0xc;
        offset = (debug_port >> 16) & 0xfff;
        dbgp_printk("bar: %02x offset: %03x\n", bar, offset);
        if (bar != PCI_BASE_ADDRESS_0) {
                dbgp_printk("only debug ports on bar 1 handled.\n");

                return -1;
        }

        bar_val = read_pci_config(bus, slot, func, PCI_BASE_ADDRESS_0);
        dbgp_printk("bar_val: %02x offset: %03x\n", bar_val, offset);
        if (bar_val & ~PCI_BASE_ADDRESS_MEM_MASK) {
                dbgp_printk("only simple 32bit mmio bars supported\n");

                return -1;
        }

        /* double check if the mem space is enabled */
        byte = read_pci_config_byte(bus, slot, func, 0x04);
        if (!(byte & 0x2)) {
                byte  |= 0x02;
                write_pci_config_byte(bus, slot, func, 0x04, byte);
                dbgp_printk("mmio for ehci enabled\n");
        }

        /*
         * FIXME I don't have the bar size so just guess PAGE_SIZE is more
         * than enough.  1K is the biggest I have seen.
         */
        set_fixmap_nocache(FIX_DBGP_BASE, bar_val & PAGE_MASK);
        ehci_bar = (void __iomem *)__fix_to_virt(FIX_DBGP_BASE);
        ehci_bar += bar_val & ~PAGE_MASK;
        dbgp_printk("ehci_bar: %p\n", ehci_bar);

        ehci_caps  = ehci_bar;
        ehci_regs  = ehci_bar + EARLY_HC_LENGTH(readl(&ehci_caps->hc_capbase));
        ehci_debug = ehci_bar + offset;
        ehci_dev.bus = bus;
        ehci_dev.slot = slot;
        ehci_dev.func = func;

        detect_set_debug_port();

        ret = ehci_setup();
        if (ret < 0) {
                dbgp_printk("ehci_setup failed\n");
                ehci_debug = NULL;

                return -1;
        }
        dbgp_ehci_status("early_init_complete");

        return 0;
}

static void early_dbgp_write(struct console *con, const char *str, u32 n)
{
        int chunk, ret;
        char buf[DBGP_MAX_PACKET];
        int use_cr = 0;
        u32 cmd, ctrl;
        int reset_run = 0;

        if (!ehci_debug || dbgp_not_safe)
                return;

        cmd = readl(&ehci_regs->command);
        if (unlikely(!(cmd & CMD_RUN))) {
                /* If the ehci controller is not in the run state do extended
                 * checks to see if the acpi or some other initialization also
                 * reset the ehci debug port */
                ctrl = readl(&ehci_debug->control);
                if (!(ctrl & DBGP_ENABLED)) {
                        dbgp_not_safe = 1;
                        _dbgp_external_startup();
                } else {
                        cmd |= CMD_RUN;
                        writel(cmd, &ehci_regs->command);
                        reset_run = 1;
                }
        }
        while (n > 0) {
                for (chunk = 0; chunk < DBGP_MAX_PACKET && n > 0;
                     str++, chunk++, n--) {
                        if (!use_cr && *str == '\n') {
                                use_cr = 1;
                                buf[chunk] = '\r';
                                str--;
                                n++;
                                continue;
                        }
                        if (use_cr)
                                use_cr = 0;
                        buf[chunk] = *str;
                }
                if (chunk > 0) {
                        ret = dbgp_bulk_write(USB_DEBUG_DEVNUM,
                                      dbgp_endpoint_out, buf, chunk);
                }
        }
        if (unlikely(reset_run)) {
                cmd = readl(&ehci_regs->command);
                cmd &= ~CMD_RUN;
                writel(cmd, &ehci_regs->command);
        }
}

struct console early_dbgp_console = {
        .name =         "earlydbg",
        .write =        early_dbgp_write,
        .flags =        CON_PRINTBUFFER,
        .index =        -1,
};

#if IS_ENABLED(CONFIG_USB)
int dbgp_reset_prep(struct usb_hcd *hcd)
{
        int ret = xen_dbgp_reset_prep(hcd);
        u32 ctrl;

        if (ret)
                return ret;

        dbgp_not_safe = 1;
        if (!ehci_debug)
                return 0;

        if ((early_dbgp_console.index != -1 &&
             !(early_dbgp_console.flags & CON_BOOT)) ||
            dbgp_kgdb_mode)
                return 1;
        /* This means the console is not initialized, or should get
         * shutdown so as to allow for reuse of the usb device, which
         * means it is time to shutdown the usb debug port. */
        ctrl = readl(&ehci_debug->control);
        if (ctrl & DBGP_ENABLED) {
                ctrl &= ~(DBGP_CLAIM);
                writel(ctrl, &ehci_debug->control);
        }
        return 0;
}
EXPORT_SYMBOL_GPL(dbgp_reset_prep);

int dbgp_external_startup(struct usb_hcd *hcd)
{
        return xen_dbgp_external_startup(hcd) ?: _dbgp_external_startup();
}
EXPORT_SYMBOL_GPL(dbgp_external_startup);
#endif /* USB */

#ifdef CONFIG_KGDB

static char kgdbdbgp_buf[DBGP_MAX_PACKET];
static int kgdbdbgp_buf_sz;
static int kgdbdbgp_buf_idx;
static int kgdbdbgp_loop_cnt = DBGP_LOOPS;

static int kgdbdbgp_read_char(void)
{
        int ret;

        if (kgdbdbgp_buf_idx < kgdbdbgp_buf_sz) {
                char ch = kgdbdbgp_buf[kgdbdbgp_buf_idx++];
                return ch;
        }

        ret = dbgp_bulk_read(USB_DEBUG_DEVNUM, dbgp_endpoint_in,
                             &kgdbdbgp_buf, DBGP_MAX_PACKET,
                             kgdbdbgp_loop_cnt);
        if (ret <= 0)
                return NO_POLL_CHAR;
        kgdbdbgp_buf_sz = ret;
        kgdbdbgp_buf_idx = 1;
        return kgdbdbgp_buf[0];
}

static void kgdbdbgp_write_char(u8 chr)
{
        early_dbgp_write(NULL, &chr, 1);
}

static struct kgdb_io kgdbdbgp_io_ops = {
        .name = "kgdbdbgp",
        .read_char = kgdbdbgp_read_char,
        .write_char = kgdbdbgp_write_char,
};

static int kgdbdbgp_wait_time;

static int __init kgdbdbgp_parse_config(char *str)
{
        char *ptr;

        if (!ehci_debug) {
                if (early_dbgp_init(str))
                        return -1;
        }
        ptr = strchr(str, ',');
        if (ptr) {
                ptr++;
                kgdbdbgp_wait_time = simple_strtoul(ptr, &ptr, 10);
        }
        kgdb_register_io_module(&kgdbdbgp_io_ops);
        kgdbdbgp_io_ops.is_console = early_dbgp_console.index != -1;

        return 0;
}
early_param("kgdbdbgp", kgdbdbgp_parse_config);

static int kgdbdbgp_reader_thread(void *ptr)
{
        int ret;

        while (readl(&ehci_debug->control) & DBGP_ENABLED) {
                kgdbdbgp_loop_cnt = 1;
                ret = kgdbdbgp_read_char();
                kgdbdbgp_loop_cnt = DBGP_LOOPS;
                if (ret != NO_POLL_CHAR) {
                        if (ret == 0x3 || ret == '$') {
                                if (ret == '$')
                                        kgdbdbgp_buf_idx--;
                                kgdb_breakpoint();
                        }
                        continue;
                }
                schedule_timeout_interruptible(kgdbdbgp_wait_time * HZ);
        }
        return 0;
}

static int __init kgdbdbgp_start_thread(void)
{
        if (dbgp_kgdb_mode && kgdbdbgp_wait_time)
                kthread_run(kgdbdbgp_reader_thread, NULL, "%s", "dbgp");

        return 0;
}
device_initcall(kgdbdbgp_start_thread);
#endif /* CONFIG_KGDB */