ehci-dbgp.c

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/*
 * Standalone EHCI usb debug driver
 *
 * Originally written by:
 *  Eric W. Biederman" <[email protected]> and
 *  Yinghai Lu <[email protected]>
 *
 * Changes for early/late printk and HW errata:
 *  Jason Wessel <[email protected]>
 *  Copyright (C) 2009 Wind River Systems, Inc.
 *
 */

#include <linux/console.h>
#include <linux/errno.h>
#include <linux/module.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/kconfig.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;
    }
    if (ret < 0) {
        dbgp_printk("Attached device is not a 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_EHCI_HCD)
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_EHCI_HCD */

#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;
}
module_init(kgdbdbgp_start_thread);
#endif /* CONFIG_KGDB */