Archipelago » qemu

/*

 * USB UHCI controller emulation

 *

 * Copyright (c) 2005 Fabrice Bellard

 *

 * Copyright (c) 2008 Max Krasnyansky

 *     Magor rewrite of the UHCI data structures parser and frame processor

 *     Support for fully async operation and multiple outstanding transactions

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 */

#include "hw.h"

#include "usb.h"

#include "pci.h"

#include "qemu-timer.h"

#include "usb-uhci.h"

//#define DEBUG

//#define DEBUG_DUMP_DATA

#define UHCI_CMD_FGR      (1 << 4)

#define UHCI_CMD_EGSM     (1 << 3)

#define UHCI_CMD_GRESET   (1 << 2)

#define UHCI_CMD_HCRESET  (1 << 1)

#define UHCI_CMD_RS       (1 << 0)

#define UHCI_STS_HCHALTED (1 << 5)

#define UHCI_STS_HCPERR   (1 << 4)

#define UHCI_STS_HSERR    (1 << 3)

#define UHCI_STS_RD       (1 << 2)

#define UHCI_STS_USBERR   (1 << 1)

#define UHCI_STS_USBINT   (1 << 0)

#define TD_CTRL_SPD     (1 << 29)

#define TD_CTRL_ERROR_SHIFT  27

#define TD_CTRL_IOS     (1 << 25)

#define TD_CTRL_IOC     (1 << 24)

#define TD_CTRL_ACTIVE  (1 << 23)

#define TD_CTRL_STALL   (1 << 22)

#define TD_CTRL_BABBLE  (1 << 20)

#define TD_CTRL_NAK     (1 << 19)

#define TD_CTRL_TIMEOUT (1 << 18)

#define UHCI_PORT_RESET (1 << 9)

#define UHCI_PORT_LSDA  (1 << 8)

#define UHCI_PORT_ENC   (1 << 3)

#define UHCI_PORT_EN    (1 << 2)

#define UHCI_PORT_CSC   (1 << 1)

#define UHCI_PORT_CCS   (1 << 0)

#define FRAME_TIMER_FREQ 1000

#define FRAME_MAX_LOOPS  100

#define NB_PORTS 2

#ifdef DEBUG

#define DPRINTF printf

static const char *pid2str(int pid)

{

    switch (pid) {

    case USB_TOKEN_SETUP: return "SETUP";

    case USB_TOKEN_IN:    return "IN";

    case USB_TOKEN_OUT:   return "OUT";

    }

    return "?";

}

#else

#define DPRINTF(...)

#endif

#ifdef DEBUG_DUMP_DATA

static void dump_data(const uint8_t *data, int len)

{

    int i;

    printf("uhci: data: ");

    for(i = 0; i < len; i++)

        printf(" %02x", data[i]);

    printf("\n");

}

#else

static void dump_data(const uint8_t *data, int len) {}

#endif

/* 

 * Pending async transaction.

 * 'packet' must be the first field because completion

 * handler does "(UHCIAsync *) pkt" cast.

 */

typedef struct UHCIAsync {

    USBPacket packet;

    struct UHCIAsync *next;

    uint32_t  td;

    uint32_t  token;

    int8_t    valid;

    uint8_t   isoc;

    uint8_t   done;

    uint8_t   buffer[2048];

} UHCIAsync;

typedef struct UHCIPort {

    USBPort port;

    uint16_t ctrl;

} UHCIPort;

typedef struct UHCIState {

    PCIDevice dev;

    USBBus bus;

    uint16_t cmd; /* cmd register */

    uint16_t status;

    uint16_t intr; /* interrupt enable register */

    uint16_t frnum; /* frame number */

    uint32_t fl_base_addr; /* frame list base address */

    uint8_t sof_timing;

    uint8_t status2; /* bit 0 and 1 are used to generate UHCI_STS_USBINT */

    int64_t expire_time;

    QEMUTimer *frame_timer;

    UHCIPort ports[NB_PORTS];

    /* Interrupts that should be raised at the end of the current frame.  */

    uint32_t pending_int_mask;

    /* Active packets */

    UHCIAsync *async_pending;

    UHCIAsync *async_pool;

    uint8_t num_ports_vmstate;

} UHCIState;

typedef struct UHCI_TD {

    uint32_t link;

    uint32_t ctrl; /* see TD_CTRL_xxx */

    uint32_t token;

    uint32_t buffer;

} UHCI_TD;

typedef struct UHCI_QH {

    uint32_t link;

    uint32_t el_link;

} UHCI_QH;

static UHCIAsync *uhci_async_alloc(UHCIState *s)

{

    UHCIAsync *async = qemu_malloc(sizeof(UHCIAsync));

    memset(&async->packet, 0, sizeof(async->packet));

    async->valid = 0;

    async->td    = 0;

    async->token = 0;

    async->done  = 0;

    async->isoc  = 0;

    async->next  = NULL;

    return async;

}

static void uhci_async_free(UHCIState *s, UHCIAsync *async)

{

    qemu_free(async);

}

static void uhci_async_link(UHCIState *s, UHCIAsync *async)

{

    async->next = s->async_pending;

    s->async_pending = async;

}

static void uhci_async_unlink(UHCIState *s, UHCIAsync *async)

{

    UHCIAsync *curr = s->async_pending;

    UHCIAsync **prev = &s->async_pending;

    while (curr) {

        if (curr == async) {

            *prev = curr->next;

            return;

        }

        prev = &curr->next;

        curr = curr->next;

    }

}

static void uhci_async_cancel(UHCIState *s, UHCIAsync *async)

{

    DPRINTF("uhci: cancel td 0x%x token 0x%x done %u\n",

           async->td, async->token, async->done);

    if (!async->done)

        usb_cancel_packet(&async->packet);

    uhci_async_free(s, async);

}

/*

 * Mark all outstanding async packets as invalid.

 * This is used for canceling them when TDs are removed by the HCD.

 */

static UHCIAsync *uhci_async_validate_begin(UHCIState *s)

{

    UHCIAsync *async = s->async_pending;

    while (async) {

        async->valid--;

        async = async->next;

    }

    return NULL;

}

/*

 * Cancel async packets that are no longer valid

 */

static void uhci_async_validate_end(UHCIState *s)

{

    UHCIAsync *curr = s->async_pending;

    UHCIAsync **prev = &s->async_pending;

    UHCIAsync *next;

    while (curr) {

        if (curr->valid > 0) {

            prev = &curr->next;

            curr = curr->next;

            continue;

        }

        next = curr->next;

        /* Unlink */

        *prev = next;

        uhci_async_cancel(s, curr);

        curr = next;

    }

}

static void uhci_async_cancel_all(UHCIState *s)

{

    UHCIAsync *curr = s->async_pending;

    UHCIAsync *next;

    while (curr) {

        next = curr->next;

        uhci_async_cancel(s, curr);

        curr = next;

    }

    s->async_pending = NULL;

}

static UHCIAsync *uhci_async_find_td(UHCIState *s, uint32_t addr, uint32_t token)

{

    UHCIAsync *async = s->async_pending;

    UHCIAsync *match = NULL;

    int count = 0;

    /*

     * We're looking for the best match here. ie both td addr and token.

     * Otherwise we return last good match. ie just token.

     * It's ok to match just token because it identifies the transaction

     * rather well, token includes: device addr, endpoint, size, etc.

     *

     * Also since we queue async transactions in reverse order by returning

     * last good match we restores the order.

     *

     * It's expected that we wont have a ton of outstanding transactions.

     * If we ever do we'd want to optimize this algorithm.

     */

    while (async) {

        if (async->token == token) {

            /* Good match */

            match = async;

            if (async->td == addr) {

                /* Best match */

                break;

            }

        }

        async = async->next;

        count++;

    }

    if (count > 64)

        fprintf(stderr, "uhci: warning lots of async transactions\n");

    return match;

}

static void uhci_attach(USBPort *port1, USBDevice *dev);

static void uhci_update_irq(UHCIState *s)

{

    int level;

    if (((s->status2 & 1) && (s->intr & (1 << 2))) ||

        ((s->status2 & 2) && (s->intr & (1 << 3))) ||

        ((s->status & UHCI_STS_USBERR) && (s->intr & (1 << 0))) ||

        ((s->status & UHCI_STS_RD) && (s->intr & (1 << 1))) ||

        (s->status & UHCI_STS_HSERR) ||

        (s->status & UHCI_STS_HCPERR)) {

        level = 1;

    } else {

        level = 0;

    }

    qemu_set_irq(s->dev.irq[3], level);

}

static void uhci_reset(void *opaque)

{

    UHCIState *s = opaque;

    uint8_t *pci_conf;

    int i;

    UHCIPort *port;

    DPRINTF("uhci: full reset\n");

    pci_conf = s->dev.config;

    pci_conf[0x6a] = 0x01; /* usb clock */

    pci_conf[0x6b] = 0x00;

    s->cmd = 0;

    s->status = 0;

    s->status2 = 0;

    s->intr = 0;

    s->fl_base_addr = 0;

    s->sof_timing = 64;

    for(i = 0; i < NB_PORTS; i++) {

        port = &s->ports[i];

        port->ctrl = 0x0080;

        if (port->port.dev)

            uhci_attach(&port->port, port->port.dev);

    }

    uhci_async_cancel_all(s);

}

static void uhci_pre_save(void *opaque)

{

    UHCIState *s = opaque;

    uhci_async_cancel_all(s);

}

static const VMStateDescription vmstate_uhci_port = {

    .name = "uhci port",

    .version_id = 1,

    .minimum_version_id = 1,

    .minimum_version_id_old = 1,

    .fields      = (VMStateField []) {

        VMSTATE_UINT16(ctrl, UHCIPort),

        VMSTATE_END_OF_LIST()

    }

};

static const VMStateDescription vmstate_uhci = {

    .name = "uhci",

    .version_id = 2,

    .minimum_version_id = 1,

    .minimum_version_id_old = 1,

    .pre_save = uhci_pre_save,

    .fields      = (VMStateField []) {

        VMSTATE_PCI_DEVICE(dev, UHCIState),

        VMSTATE_UINT8_EQUAL(num_ports_vmstate, UHCIState),

        VMSTATE_STRUCT_ARRAY(ports, UHCIState, NB_PORTS, 1,

                             vmstate_uhci_port, UHCIPort),

        VMSTATE_UINT16(cmd, UHCIState),

        VMSTATE_UINT16(status, UHCIState),

        VMSTATE_UINT16(intr, UHCIState),

        VMSTATE_UINT16(frnum, UHCIState),

        VMSTATE_UINT32(fl_base_addr, UHCIState),

        VMSTATE_UINT8(sof_timing, UHCIState),

        VMSTATE_UINT8(status2, UHCIState),

        VMSTATE_TIMER(frame_timer, UHCIState),

        VMSTATE_INT64_V(expire_time, UHCIState, 2),

        VMSTATE_END_OF_LIST()

    }

};

static void uhci_ioport_writeb(void *opaque, uint32_t addr, uint32_t val)

{

    UHCIState *s = opaque;

    addr &= 0x1f;

    switch(addr) {

    case 0x0c:

        s->sof_timing = val;

        break;

    }

}

static uint32_t uhci_ioport_readb(void *opaque, uint32_t addr)

{

    UHCIState *s = opaque;

    uint32_t val;

    addr &= 0x1f;

    switch(addr) {

    case 0x0c:

        val = s->sof_timing;

        break;

    default:

        val = 0xff;

        break;

    }

    return val;

}

static void uhci_ioport_writew(void *opaque, uint32_t addr, uint32_t val)

{

    UHCIState *s = opaque;

    addr &= 0x1f;

    DPRINTF("uhci: writew port=0x%04x val=0x%04x\n", addr, val);

    switch(addr) {

    case 0x00:

        if ((val & UHCI_CMD_RS) && !(s->cmd & UHCI_CMD_RS)) {

            /* start frame processing */

            qemu_mod_timer(s->frame_timer, qemu_get_clock(vm_clock));

            s->status &= ~UHCI_STS_HCHALTED;

        } else if (!(val & UHCI_CMD_RS)) {

            s->status |= UHCI_STS_HCHALTED;

        }

        if (val & UHCI_CMD_GRESET) {

            UHCIPort *port;

            USBDevice *dev;

            int i;

            /* send reset on the USB bus */

            for(i = 0; i < NB_PORTS; i++) {

                port = &s->ports[i];

                dev = port->port.dev;

                if (dev) {

                    usb_send_msg(dev, USB_MSG_RESET);

                }

            }

            uhci_reset(s);

            return;

        }

        if (val & UHCI_CMD_HCRESET) {

            uhci_reset(s);

            return;

        }

        s->cmd = val;

        break;

    case 0x02:

        s->status &= ~val;

        /* XXX: the chip spec is not coherent, so we add a hidden

           register to distinguish between IOC and SPD */

        if (val & UHCI_STS_USBINT)

            s->status2 = 0;

        uhci_update_irq(s);

        break;

    case 0x04:

        s->intr = val;

        uhci_update_irq(s);

        break;

    case 0x06:

        if (s->status & UHCI_STS_HCHALTED)

            s->frnum = val & 0x7ff;

        break;

    case 0x10 ... 0x1f:

        {

            UHCIPort *port;

            USBDevice *dev;

            int n;

            n = (addr >> 1) & 7;

            if (n >= NB_PORTS)

                return;

            port = &s->ports[n];

            dev = port->port.dev;

            if (dev) {

                /* port reset */

                if ( (val & UHCI_PORT_RESET) &&

                     !(port->ctrl & UHCI_PORT_RESET) ) {

                    usb_send_msg(dev, USB_MSG_RESET);

                }

            }

            port->ctrl = (port->ctrl & 0x01fb) | (val & ~0x01fb);

            /* some bits are reset when a '1' is written to them */

            port->ctrl &= ~(val & 0x000a);

        }

        break;

    }

}

static uint32_t uhci_ioport_readw(void *opaque, uint32_t addr)

{

    UHCIState *s = opaque;

    uint32_t val;

    addr &= 0x1f;

    switch(addr) {

    case 0x00:

        val = s->cmd;

        break;

    case 0x02:

        val = s->status;

        break;

    case 0x04:

        val = s->intr;

        break;

    case 0x06:

        val = s->frnum;

        break;

    case 0x10 ... 0x1f:

        {

            UHCIPort *port;

            int n;

            n = (addr >> 1) & 7;

            if (n >= NB_PORTS)

                goto read_default;

            port = &s->ports[n];

            val = port->ctrl;

        }

        break;

    default:

    read_default:

        val = 0xff7f; /* disabled port */

        break;

    }

    DPRINTF("uhci: readw port=0x%04x val=0x%04x\n", addr, val);

    return val;

}

static void uhci_ioport_writel(void *opaque, uint32_t addr, uint32_t val)

{

    UHCIState *s = opaque;

    addr &= 0x1f;

    DPRINTF("uhci: writel port=0x%04x val=0x%08x\n", addr, val);

    switch(addr) {

    case 0x08:

        s->fl_base_addr = val & ~0xfff;

        break;

    }

}

static uint32_t uhci_ioport_readl(void *opaque, uint32_t addr)

{

    UHCIState *s = opaque;

    uint32_t val;

    addr &= 0x1f;

    switch(addr) {

    case 0x08:

        val = s->fl_base_addr;

        break;

    default:

        val = 0xffffffff;

        break;

    }

    return val;

}

/* signal resume if controller suspended */

static void uhci_resume (void *opaque)

{

    UHCIState *s = (UHCIState *)opaque;

    if (!s)

        return;

    if (s->cmd & UHCI_CMD_EGSM) {

        s->cmd |= UHCI_CMD_FGR;

        s->status |= UHCI_STS_RD;

        uhci_update_irq(s);

    }

}

static void uhci_attach(USBPort *port1, USBDevice *dev)

{

    UHCIState *s = port1->opaque;

    UHCIPort *port = &s->ports[port1->index];

    if (dev) {

        if (port->port.dev) {

            usb_attach(port1, NULL);

        }

        /* set connect status */

        port->ctrl |= UHCI_PORT_CCS | UHCI_PORT_CSC;

        /* update speed */

        if (dev->speed == USB_SPEED_LOW)

            port->ctrl |= UHCI_PORT_LSDA;

        else

            port->ctrl &= ~UHCI_PORT_LSDA;

        uhci_resume(s);

        port->port.dev = dev;

        /* send the attach message */

        usb_send_msg(dev, USB_MSG_ATTACH);

    } else {

        /* set connect status */

        if (port->ctrl & UHCI_PORT_CCS) {

            port->ctrl &= ~UHCI_PORT_CCS;

            port->ctrl |= UHCI_PORT_CSC;

        }

        /* disable port */

        if (port->ctrl & UHCI_PORT_EN) {

            port->ctrl &= ~UHCI_PORT_EN;

            port->ctrl |= UHCI_PORT_ENC;

        }

        uhci_resume(s);

        dev = port->port.dev;

        if (dev) {

            /* send the detach message */

            usb_send_msg(dev, USB_MSG_DETACH);

        }

        port->port.dev = NULL;

    }

}

static int uhci_broadcast_packet(UHCIState *s, USBPacket *p)

{

    int i, ret;

    DPRINTF("uhci: packet enter. pid %s addr 0x%02x ep %d len %d\n",

           pid2str(p->pid), p->devaddr, p->devep, p->len);

    if (p->pid == USB_TOKEN_OUT || p->pid == USB_TOKEN_SETUP)

        dump_data(p->data, p->len);

    ret = USB_RET_NODEV;

    for (i = 0; i < NB_PORTS && ret == USB_RET_NODEV; i++) {

        UHCIPort *port = &s->ports[i];

        USBDevice *dev = port->port.dev;

        if (dev && (port->ctrl & UHCI_PORT_EN))

            ret = dev->info->handle_packet(dev, p);

    }

    DPRINTF("uhci: packet exit. ret %d len %d\n", ret, p->len);

    if (p->pid == USB_TOKEN_IN && ret > 0)

        dump_data(p->data, ret);

    return ret;

}

static void uhci_async_complete(USBPacket * packet, void *opaque);

static void uhci_process_frame(UHCIState *s);

/* return -1 if fatal error (frame must be stopped)

          0 if TD successful

          1 if TD unsuccessful or inactive

*/

static int uhci_complete_td(UHCIState *s, UHCI_TD *td, UHCIAsync *async, uint32_t *int_mask)

{

    int len = 0, max_len, err, ret;

    uint8_t pid;

    max_len = ((td->token >> 21) + 1) & 0x7ff;

    pid = td->token & 0xff;

    ret = async->packet.len;

    if (td->ctrl & TD_CTRL_IOS)

        td->ctrl &= ~TD_CTRL_ACTIVE;

    if (ret < 0)

        goto out;

    len = async->packet.len;

    td->ctrl = (td->ctrl & ~0x7ff) | ((len - 1) & 0x7ff);

    /* The NAK bit may have been set by a previous frame, so clear it

       here.  The docs are somewhat unclear, but win2k relies on this

       behavior.  */

    td->ctrl &= ~(TD_CTRL_ACTIVE | TD_CTRL_NAK);

    if (td->ctrl & TD_CTRL_IOC)

        *int_mask |= 0x01;

    if (pid == USB_TOKEN_IN) {

        if (len > max_len) {

            ret = USB_RET_BABBLE;

            goto out;

        }

        if (len > 0) {

            /* write the data back */

            cpu_physical_memory_write(td->buffer, async->buffer, len);

        }

        if ((td->ctrl & TD_CTRL_SPD) && len < max_len) {

            *int_mask |= 0x02;

            /* short packet: do not update QH */

            DPRINTF("uhci: short packet. td 0x%x token 0x%x\n", async->td, async->token);

            return 1;

        }

    }

    /* success */

    return 0;

out:

    switch(ret) {

    case USB_RET_STALL:

        td->ctrl |= TD_CTRL_STALL;

        td->ctrl &= ~TD_CTRL_ACTIVE;

        return 1;

    case USB_RET_BABBLE:

        td->ctrl |= TD_CTRL_BABBLE | TD_CTRL_STALL;

        td->ctrl &= ~TD_CTRL_ACTIVE;

        /* frame interrupted */

        return -1;

    case USB_RET_NAK:

        td->ctrl |= TD_CTRL_NAK;

        if (pid == USB_TOKEN_SETUP)

            break;

        return 1;

    case USB_RET_NODEV:

    default:

        break;

    }

    /* Retry the TD if error count is not zero */

    td->ctrl |= TD_CTRL_TIMEOUT;

    err = (td->ctrl >> TD_CTRL_ERROR_SHIFT) & 3;

    if (err != 0) {

        err--;

        if (err == 0) {

            td->ctrl &= ~TD_CTRL_ACTIVE;

            s->status |= UHCI_STS_USBERR;

            if (td->ctrl & TD_CTRL_IOC)

                *int_mask |= 0x01;

            uhci_update_irq(s);

        }

    }

    td->ctrl = (td->ctrl & ~(3 << TD_CTRL_ERROR_SHIFT)) |

        (err << TD_CTRL_ERROR_SHIFT);

    return 1;

}

static int uhci_handle_td(UHCIState *s, uint32_t addr, UHCI_TD *td, uint32_t *int_mask)

{

    UHCIAsync *async;

    int len = 0, max_len;

    uint8_t pid, isoc;

    uint32_t token;

    /* Is active ? */

    if (!(td->ctrl & TD_CTRL_ACTIVE))

        return 1;

    /* token field is not unique for isochronous requests,

     * so use the destination buffer 

     */

    if (td->ctrl & TD_CTRL_IOS) {

        token = td->buffer;

        isoc = 1;

    } else {

        token = td->token;

        isoc = 0;

    }

    async = uhci_async_find_td(s, addr, token);

    if (async) {

        /* Already submitted */

        async->valid = 32;

        if (!async->done)

            return 1;

        uhci_async_unlink(s, async);

        goto done;

    }

    /* Allocate new packet */

    async = uhci_async_alloc(s);

    if (!async)

        return 1;

    /* valid needs to be large enough to handle 10 frame delay

     * for initial isochronous requests

     */

    async->valid = 32;

    async->td    = addr;

    async->token = token;

    async->isoc  = isoc;

    max_len = ((td->token >> 21) + 1) & 0x7ff;

    pid = td->token & 0xff;

    async->packet.pid     = pid;

    async->packet.devaddr = (td->token >> 8) & 0x7f;

    async->packet.devep   = (td->token >> 15) & 0xf;

    async->packet.data    = async->buffer;

    async->packet.len     = max_len;

    async->packet.complete_cb     = uhci_async_complete;

    async->packet.complete_opaque = s;

    switch(pid) {

    case USB_TOKEN_OUT:

    case USB_TOKEN_SETUP:

        cpu_physical_memory_read(td->buffer, async->buffer, max_len);

        len = uhci_broadcast_packet(s, &async->packet);

        if (len >= 0)

            len = max_len;

        break;

    case USB_TOKEN_IN:

        len = uhci_broadcast_packet(s, &async->packet);

        break;

    default:

        /* invalid pid : frame interrupted */

        uhci_async_free(s, async);

        s->status |= UHCI_STS_HCPERR;

        uhci_update_irq(s);

        return -1;

    }

    if (len == USB_RET_ASYNC) {

        uhci_async_link(s, async);

        return 2;

    }

    async->packet.len = len;

done:

    len = uhci_complete_td(s, td, async, int_mask);

    uhci_async_free(s, async);

    return len;

}

static void uhci_async_complete(USBPacket *packet, void *opaque)

{

    UHCIState *s = opaque;

    UHCIAsync *async = (UHCIAsync *) packet;

    DPRINTF("uhci: async complete. td 0x%x token 0x%x\n", async->td, async->token);

    if (async->isoc) {

        UHCI_TD td;

        uint32_t link = async->td;

        uint32_t int_mask = 0, val;

        cpu_physical_memory_read(link & ~0xf, (uint8_t *) &td, sizeof(td));

        le32_to_cpus(&td.link);

        le32_to_cpus(&td.ctrl);

        le32_to_cpus(&td.token);

        le32_to_cpus(&td.buffer);

        uhci_async_unlink(s, async);

        uhci_complete_td(s, &td, async, &int_mask);

        s->pending_int_mask |= int_mask;

        /* update the status bits of the TD */

        val = cpu_to_le32(td.ctrl);

        cpu_physical_memory_write((link & ~0xf) + 4,

                                  (const uint8_t *)&val, sizeof(val));

        uhci_async_free(s, async);

    } else {

        async->done = 1;

        uhci_process_frame(s);

    }

}

static int is_valid(uint32_t link)

{

    return (link & 1) == 0;

}

static int is_qh(uint32_t link)

{

    return (link & 2) != 0;

}

static int depth_first(uint32_t link)

{

    return (link & 4) != 0;

}