blob: 3c0be136869c94a32c8df771b10685674ca1a66f [file] [log] [blame]
// Code for handling EHCI USB controllers.
//
// Copyright (C) 2010 Kevin O'Connor <kevin@koconnor.net>
//
// This file may be distributed under the terms of the GNU LGPLv3 license.
#include "util.h" // dprintf
#include "pci.h" // pci_bdf_to_bus
#include "config.h" // CONFIG_*
#include "ioport.h" // outw
#include "usb-ehci.h" // struct ehci_qh
#include "pci_ids.h" // PCI_CLASS_SERIAL_USB_UHCI
#include "pci_regs.h" // PCI_BASE_ADDRESS_0
#include "usb.h" // struct usb_s
#include "biosvar.h" // GET_LOWFLAT
#include "usb-uhci.h" // init_uhci
#include "usb-ohci.h" // init_ohci
struct usb_ehci_s {
struct usb_s usb;
struct ehci_caps *caps;
struct ehci_regs *regs;
struct ehci_qh *async_qh;
struct pci_device *companion[8];
int checkports;
int legacycount;
};
struct ehci_pipe {
struct ehci_qh qh;
struct ehci_qtd *next_td, *tds;
void *data;
struct usb_pipe pipe;
};
/****************************************************************
* Root hub
****************************************************************/
#define EHCI_TIME_POSTPOWER 20
#define EHCI_TIME_POSTRESET 2
// Check if need companion controllers for full/low speed devices
static void
ehci_note_port(struct usb_ehci_s *cntl)
{
if (--cntl->checkports)
// Ports still being detected.
return;
if (! cntl->legacycount)
// No full/low speed devices found.
return;
// Start companion controllers.
int i;
for (i=0; i<ARRAY_SIZE(cntl->companion); i++) {
struct pci_device *pci = cntl->companion[i];
if (!pci)
break;
// ohci/uhci_init call pci_config_XXX - don't run from irq handler.
wait_preempt();
if (pci_classprog(pci) == PCI_CLASS_SERIAL_USB_UHCI)
uhci_init(pci, cntl->usb.busid + i);
else if (pci_classprog(pci) == PCI_CLASS_SERIAL_USB_OHCI)
ohci_init(pci, cntl->usb.busid + i);
}
}
// Check if device attached to port
static int
ehci_hub_detect(struct usbhub_s *hub, u32 port)
{
struct usb_ehci_s *cntl = container_of(hub->cntl, struct usb_ehci_s, usb);
u32 *portreg = &cntl->regs->portsc[port];
u32 portsc = readl(portreg);
// Power up port.
if (!(portsc & PORT_POWER)) {
portsc |= PORT_POWER;
writel(portreg, portsc);
msleep(EHCI_TIME_POSTPOWER);
} else {
msleep(1); // XXX - time for connect to be detected.
}
portsc = readl(portreg);
if (!(portsc & PORT_CONNECT))
// No device present
goto doneearly;
if ((portsc & PORT_LINESTATUS_MASK) == PORT_LINESTATUS_KSTATE) {
// low speed device
cntl->legacycount++;
writel(portreg, portsc | PORT_OWNER);
goto doneearly;
}
// XXX - if just powered up, need to wait for USB_TIME_ATTDB?
// Begin reset on port
portsc = (portsc & ~PORT_PE) | PORT_RESET;
writel(portreg, portsc);
msleep(USB_TIME_DRSTR);
return 0;
doneearly:
ehci_note_port(cntl);
return -1;
}
// Reset device on port
static int
ehci_hub_reset(struct usbhub_s *hub, u32 port)
{
struct usb_ehci_s *cntl = container_of(hub->cntl, struct usb_ehci_s, usb);
u32 *portreg = &cntl->regs->portsc[port];
u32 portsc = readl(portreg);
// Finish reset on port
portsc &= ~PORT_RESET;
writel(portreg, portsc);
msleep(EHCI_TIME_POSTRESET);
int rv = -1;
portsc = readl(portreg);
if (!(portsc & PORT_CONNECT))
// No longer connected
goto resetfail;
if (!(portsc & PORT_PE)) {
// full speed device
cntl->legacycount++;
writel(portreg, portsc | PORT_OWNER);
goto resetfail;
}
rv = USB_HIGHSPEED;
resetfail:
ehci_note_port(cntl);
return rv;
}
// Disable port
static void
ehci_hub_disconnect(struct usbhub_s *hub, u32 port)
{
struct usb_ehci_s *cntl = container_of(hub->cntl, struct usb_ehci_s, usb);
u32 *portreg = &cntl->regs->portsc[port];
u32 portsc = readl(portreg);
writel(portreg, portsc & ~PORT_PE);
}
static struct usbhub_op_s ehci_HubOp = {
.detect = ehci_hub_detect,
.reset = ehci_hub_reset,
.disconnect = ehci_hub_disconnect,
};
// Find any devices connected to the root hub.
static int
check_ehci_ports(struct usb_ehci_s *cntl)
{
ASSERT32FLAT();
struct usbhub_s hub;
memset(&hub, 0, sizeof(hub));
hub.cntl = &cntl->usb;
hub.portcount = cntl->checkports;
hub.op = &ehci_HubOp;
usb_enumerate(&hub);
return hub.devcount;
}
/****************************************************************
* Setup
****************************************************************/
// Wait for next USB async frame to start - for ensuring safe memory release.
static void
ehci_waittick(struct usb_ehci_s *cntl)
{
if (MODE16) {
msleep(10);
return;
}
// Wait for access to "doorbell"
barrier();
u32 cmd, sts;
u64 end = calc_future_tsc(100);
for (;;) {
sts = readl(&cntl->regs->usbsts);
if (!(sts & STS_IAA)) {
cmd = readl(&cntl->regs->usbcmd);
if (!(cmd & CMD_IAAD))
break;
}
if (check_tsc(end)) {
warn_timeout();
return;
}
yield();
}
// Ring "doorbell"
writel(&cntl->regs->usbcmd, cmd | CMD_IAAD);
// Wait for completion
for (;;) {
sts = readl(&cntl->regs->usbsts);
if (sts & STS_IAA)
break;
if (check_tsc(end)) {
warn_timeout();
return;
}
yield();
}
// Ack completion
writel(&cntl->regs->usbsts, STS_IAA);
}
static void
ehci_free_pipes(struct usb_ehci_s *cntl)
{
dprintf(7, "ehci_free_pipes %p\n", cntl);
struct ehci_qh *start = cntl->async_qh;
struct ehci_qh *pos = start;
for (;;) {
struct ehci_qh *next = (void*)(pos->next & ~EHCI_PTR_BITS);
if (next == start)
break;
struct ehci_pipe *pipe = container_of(next, struct ehci_pipe, qh);
if (pipe->pipe.cntl != &cntl->usb)
pos->next = next->next;
else
pos = next;
}
ehci_waittick(cntl);
for (;;) {
struct usb_pipe *usbpipe = cntl->usb.freelist;
if (!usbpipe)
break;
cntl->usb.freelist = usbpipe->freenext;
struct ehci_pipe *pipe = container_of(usbpipe, struct ehci_pipe, pipe);
free(pipe);
}
}
static void
configure_ehci(void *data)
{
struct usb_ehci_s *cntl = data;
// Allocate ram for schedule storage
struct ehci_framelist *fl = memalign_high(sizeof(*fl), sizeof(*fl));
struct ehci_qh *intr_qh = memalign_high(EHCI_QH_ALIGN, sizeof(*intr_qh));
struct ehci_qh *async_qh = memalign_high(EHCI_QH_ALIGN, sizeof(*async_qh));
if (!fl || !intr_qh || !async_qh) {
warn_noalloc();
goto fail;
}
// XXX - check for halted?
// Reset the HC
u32 cmd = readl(&cntl->regs->usbcmd);
writel(&cntl->regs->usbcmd, (cmd & ~(CMD_ASE | CMD_PSE)) | CMD_HCRESET);
u64 end = calc_future_tsc(250);
for (;;) {
cmd = readl(&cntl->regs->usbcmd);
if (!(cmd & CMD_HCRESET))
break;
if (check_tsc(end)) {
warn_timeout();
goto fail;
}
yield();
}
// Disable interrupts (just to be safe).
writel(&cntl->regs->usbintr, 0);
// Set schedule to point to primary intr queue head
memset(intr_qh, 0, sizeof(*intr_qh));
intr_qh->next = EHCI_PTR_TERM;
intr_qh->info2 = (0x01 << QH_SMASK_SHIFT);
intr_qh->token = QTD_STS_HALT;
intr_qh->qtd_next = intr_qh->alt_next = EHCI_PTR_TERM;
int i;
for (i=0; i<ARRAY_SIZE(fl->links); i++)
fl->links[i] = (u32)intr_qh | EHCI_PTR_QH;
writel(&cntl->regs->periodiclistbase, (u32)fl);
// Set async list to point to primary async queue head
memset(async_qh, 0, sizeof(*async_qh));
async_qh->next = (u32)async_qh | EHCI_PTR_QH;
async_qh->info1 = QH_HEAD;
async_qh->token = QTD_STS_HALT;
async_qh->qtd_next = async_qh->alt_next = EHCI_PTR_TERM;
cntl->async_qh = async_qh;
writel(&cntl->regs->asynclistbase, (u32)async_qh);
// Enable queues
writel(&cntl->regs->usbcmd, cmd | CMD_ASE | CMD_PSE | CMD_RUN);
// Set default of high speed for root hub.
writel(&cntl->regs->configflag, 1);
cntl->checkports = readl(&cntl->caps->hcsparams) & HCS_N_PORTS_MASK;
// Find devices
int count = check_ehci_ports(cntl);
ehci_free_pipes(cntl);
if (count)
// Success
return;
// No devices found - shutdown and free controller.
writel(&cntl->regs->usbcmd, cmd & ~CMD_RUN);
msleep(4); // 2ms to stop reading memory - XXX
fail:
free(fl);
free(intr_qh);
free(async_qh);
free(cntl);
}
int
ehci_init(struct pci_device *pci, int busid, struct pci_device *comppci)
{
if (! CONFIG_USB_EHCI)
return -1;
u16 bdf = pci->bdf;
u32 baseaddr = pci_config_readl(bdf, PCI_BASE_ADDRESS_0);
struct ehci_caps *caps = (void*)(baseaddr & PCI_BASE_ADDRESS_MEM_MASK);
u32 hcc_params = readl(&caps->hccparams);
struct usb_ehci_s *cntl = malloc_tmphigh(sizeof(*cntl));
if (!cntl) {
warn_noalloc();
return -1;
}
memset(cntl, 0, sizeof(*cntl));
cntl->usb.busid = busid;
cntl->usb.pci = pci;
cntl->usb.type = USB_TYPE_EHCI;
cntl->caps = caps;
if (hcc_params & HCC_64BIT_ADDR)
cntl->regs->ctrldssegment = 0;
cntl->regs = (void*)caps + readb(&caps->caplength);
dprintf(1, "EHCI init on dev %02x:%02x.%x (regs=%p)\n"
, pci_bdf_to_bus(bdf), pci_bdf_to_dev(bdf)
, pci_bdf_to_fn(bdf), cntl->regs);
pci_config_maskw(bdf, PCI_COMMAND, 0, PCI_COMMAND_MASTER);
// XXX - check for and disable SMM control?
// Find companion controllers.
int count = 0;
for (;;) {
if (!comppci || comppci == pci)
break;
if (pci_classprog(comppci) == PCI_CLASS_SERIAL_USB_UHCI)
cntl->companion[count++] = comppci;
else if (pci_classprog(comppci) == PCI_CLASS_SERIAL_USB_OHCI)
cntl->companion[count++] = comppci;
comppci = comppci->next;
}
run_thread(configure_ehci, cntl);
return 0;
}
/****************************************************************
* End point communication
****************************************************************/
// Setup fields in qh
static void
ehci_desc2pipe(struct ehci_pipe *pipe, struct usbdevice_s *usbdev
, struct usb_endpoint_descriptor *epdesc)
{
usb_desc2pipe(&pipe->pipe, usbdev, epdesc);
pipe->qh.info1 = ((pipe->pipe.maxpacket << QH_MAXPACKET_SHIFT)
| (pipe->pipe.speed << QH_SPEED_SHIFT)
| (pipe->pipe.ep << QH_EP_SHIFT)
| (pipe->pipe.devaddr << QH_DEVADDR_SHIFT));
pipe->qh.info2 = (1 << QH_MULT_SHIFT);
struct usbdevice_s *hubdev = usbdev->hub->usbdev;
if (hubdev) {
struct ehci_pipe *hpipe = container_of(
hubdev->defpipe, struct ehci_pipe, pipe);
if (hpipe->pipe.speed == USB_HIGHSPEED)
pipe->qh.info2 |= ((usbdev->port << QH_HUBPORT_SHIFT)
| (hpipe->pipe.devaddr << QH_HUBADDR_SHIFT));
else
pipe->qh.info2 = hpipe->qh.info2;
}
u8 eptype = epdesc->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK;
if (eptype == USB_ENDPOINT_XFER_CONTROL)
pipe->qh.info1 |= ((pipe->pipe.speed != USB_HIGHSPEED ? QH_CONTROL : 0)
| QH_TOGGLECONTROL);
else if (eptype == USB_ENDPOINT_XFER_INT)
pipe->qh.info2 |= (0x01 << QH_SMASK_SHIFT) | (0x1c << QH_CMASK_SHIFT);
}
static struct usb_pipe *
ehci_alloc_intr_pipe(struct usbdevice_s *usbdev
, struct usb_endpoint_descriptor *epdesc)
{
struct usb_ehci_s *cntl = container_of(
usbdev->hub->cntl, struct usb_ehci_s, usb);
int frameexp = usb_getFrameExp(usbdev, epdesc);
dprintf(7, "ehci_alloc_intr_pipe %p %d\n", &cntl->usb, frameexp);
if (frameexp > 10)
frameexp = 10;
int maxpacket = epdesc->wMaxPacketSize;
// Determine number of entries needed for 2 timer ticks.
int ms = 1<<frameexp;
int count = DIV_ROUND_UP(PIT_TICK_INTERVAL * 1000 * 2, PIT_TICK_RATE * ms);
struct ehci_pipe *pipe = memalign_low(EHCI_QH_ALIGN, sizeof(*pipe));
struct ehci_qtd *tds = memalign_low(EHCI_QTD_ALIGN, sizeof(*tds) * count);
void *data = malloc_low(maxpacket * count);
if (!pipe || !tds || !data) {
warn_noalloc();
goto fail;
}
memset(pipe, 0, sizeof(*pipe));
ehci_desc2pipe(pipe, usbdev, epdesc);
pipe->next_td = pipe->tds = tds;
pipe->data = data;
pipe->qh.qtd_next = (u32)tds;
int i;
for (i=0; i<count; i++) {
struct ehci_qtd *td = &tds[i];
td->qtd_next = (i==count-1 ? (u32)tds : (u32)&td[1]);
td->alt_next = EHCI_PTR_TERM;
td->token = (ehci_explen(maxpacket) | QTD_STS_ACTIVE
| QTD_PID_IN | ehci_maxerr(3));
td->buf[0] = (u32)data + maxpacket * i;
}
// Add to interrupt schedule.
struct ehci_framelist *fl = (void*)readl(&cntl->regs->periodiclistbase);
if (frameexp == 0) {
// Add to existing interrupt entry.
struct ehci_qh *intr_qh = (void*)(fl->links[0] & ~EHCI_PTR_BITS);
pipe->qh.next = intr_qh->next;
barrier();
intr_qh->next = (u32)&pipe->qh | EHCI_PTR_QH;
} else {
int startpos = 1<<(frameexp-1);
pipe->qh.next = fl->links[startpos];
barrier();
for (i=startpos; i<ARRAY_SIZE(fl->links); i+=ms)
fl->links[i] = (u32)&pipe->qh | EHCI_PTR_QH;
}
return &pipe->pipe;
fail:
free(pipe);
free(tds);
free(data);
return NULL;
}
struct usb_pipe *
ehci_alloc_pipe(struct usbdevice_s *usbdev
, struct usb_endpoint_descriptor *epdesc)
{
if (! CONFIG_USB_EHCI)
return NULL;
u8 eptype = epdesc->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK;
if (eptype == USB_ENDPOINT_XFER_INT)
return ehci_alloc_intr_pipe(usbdev, epdesc);
struct usb_ehci_s *cntl = container_of(
usbdev->hub->cntl, struct usb_ehci_s, usb);
dprintf(7, "ehci_alloc_async_pipe %p %d\n", &cntl->usb, eptype);
struct usb_pipe *usbpipe = usb_getFreePipe(&cntl->usb, eptype);
if (usbpipe) {
// Use previously allocated pipe.
struct ehci_pipe *pipe = container_of(usbpipe, struct ehci_pipe, pipe);
ehci_desc2pipe(pipe, usbdev, epdesc);
return usbpipe;
}
// Allocate a new queue head.
struct ehci_pipe *pipe;
if (eptype == USB_ENDPOINT_XFER_CONTROL)
pipe = memalign_tmphigh(EHCI_QH_ALIGN, sizeof(*pipe));
else
pipe = memalign_low(EHCI_QH_ALIGN, sizeof(*pipe));
if (!pipe) {
warn_noalloc();
return NULL;
}
memset(pipe, 0, sizeof(*pipe));
ehci_desc2pipe(pipe, usbdev, epdesc);
pipe->qh.qtd_next = pipe->qh.alt_next = EHCI_PTR_TERM;
// Add queue head to controller list.
struct ehci_qh *async_qh = cntl->async_qh;
pipe->qh.next = async_qh->next;
barrier();
async_qh->next = (u32)&pipe->qh | EHCI_PTR_QH;
return &pipe->pipe;
}
static void
ehci_reset_pipe(struct ehci_pipe *pipe)
{
SET_LOWFLAT(pipe->qh.qtd_next, EHCI_PTR_TERM);
SET_LOWFLAT(pipe->qh.alt_next, EHCI_PTR_TERM);
barrier();
SET_LOWFLAT(pipe->qh.token, GET_LOWFLAT(pipe->qh.token) & QTD_TOGGLE);
}
static int
ehci_wait_td(struct ehci_pipe *pipe, struct ehci_qtd *td, int timeout)
{
u64 end = calc_future_tsc(timeout);
u32 status;
for (;;) {
status = td->token;
if (!(status & QTD_STS_ACTIVE))
break;
if (check_tsc(end)) {
u32 cur = GET_LOWFLAT(pipe->qh.current);
u32 tok = GET_LOWFLAT(pipe->qh.token);
u32 next = GET_LOWFLAT(pipe->qh.qtd_next);
warn_timeout();
dprintf(1, "ehci pipe=%p cur=%08x tok=%08x next=%x td=%p status=%x\n"
, pipe, cur, tok, next, td, status);
ehci_reset_pipe(pipe);
struct usb_ehci_s *cntl = container_of(
GET_LOWFLAT(pipe->pipe.cntl), struct usb_ehci_s, usb);
ehci_waittick(cntl);
return -1;
}
yield();
}
if (status & QTD_STS_HALT) {
dprintf(1, "ehci_wait_td error - status=%x\n", status);
ehci_reset_pipe(pipe);
return -2;
}
return 0;
}
static int
fillTDbuffer(struct ehci_qtd *td, u16 maxpacket, const void *buf, int bytes)
{
u32 dest = (u32)buf;
u32 *pos = td->buf;
while (bytes) {
if (pos >= &td->buf[ARRAY_SIZE(td->buf)])
// More data than can transfer in a single qtd - only use
// full packets to prevent a babble error.
return ALIGN_DOWN(dest - (u32)buf, maxpacket);
u32 count = bytes;
u32 max = 0x1000 - (dest & 0xfff);
if (count > max)
count = max;
*pos = dest;
bytes -= count;
dest += count;
pos++;
}
return dest - (u32)buf;
}
int
ehci_control(struct usb_pipe *p, int dir, const void *cmd, int cmdsize
, void *data, int datasize)
{
ASSERT32FLAT();
if (! CONFIG_USB_EHCI)
return -1;
dprintf(5, "ehci_control %p (dir=%d cmd=%d data=%d)\n"
, p, dir, cmdsize, datasize);
if (datasize > 4*4096 || cmdsize > 4*4096) {
// XXX - should support larger sizes.
warn_noalloc();
return -1;
}
struct ehci_pipe *pipe = container_of(p, struct ehci_pipe, pipe);
// Setup transfer descriptors
struct ehci_qtd *tds = memalign_tmphigh(EHCI_QTD_ALIGN, sizeof(*tds) * 3);
if (!tds) {
warn_noalloc();
return -1;
}
memset(tds, 0, sizeof(*tds) * 3);
struct ehci_qtd *td = tds;
td->qtd_next = (u32)&td[1];
td->alt_next = EHCI_PTR_TERM;
td->token = (ehci_explen(cmdsize) | QTD_STS_ACTIVE
| QTD_PID_SETUP | ehci_maxerr(3));
u16 maxpacket = pipe->pipe.maxpacket;
fillTDbuffer(td, maxpacket, cmd, cmdsize);
td++;
if (datasize) {
td->qtd_next = (u32)&td[1];
td->alt_next = EHCI_PTR_TERM;
td->token = (QTD_TOGGLE | ehci_explen(datasize) | QTD_STS_ACTIVE
| (dir ? QTD_PID_IN : QTD_PID_OUT) | ehci_maxerr(3));
fillTDbuffer(td, maxpacket, data, datasize);
td++;
}
td->qtd_next = EHCI_PTR_TERM;
td->alt_next = EHCI_PTR_TERM;
td->token = (QTD_TOGGLE | QTD_STS_ACTIVE
| (dir ? QTD_PID_OUT : QTD_PID_IN) | ehci_maxerr(3));
// Transfer data
barrier();
pipe->qh.qtd_next = (u32)tds;
int i, ret=0;
for (i=0; i<3; i++) {
struct ehci_qtd *td = &tds[i];
ret = ehci_wait_td(pipe, td, 500);
if (ret)
break;
}
free(tds);
return ret;
}
#define STACKQTDS 4
int
ehci_send_bulk(struct usb_pipe *p, int dir, void *data, int datasize)
{
if (! CONFIG_USB_EHCI)
return -1;
struct ehci_pipe *pipe = container_of(p, struct ehci_pipe, pipe);
dprintf(7, "ehci_send_bulk qh=%p dir=%d data=%p size=%d\n"
, &pipe->qh, dir, data, datasize);
// Allocate 4 tds on stack (with required alignment)
u8 tdsbuf[sizeof(struct ehci_qtd) * STACKQTDS + EHCI_QTD_ALIGN - 1];
struct ehci_qtd *tds = (void*)ALIGN((u32)tdsbuf, EHCI_QTD_ALIGN);
memset(tds, 0, sizeof(*tds) * STACKQTDS);
barrier();
SET_LOWFLAT(pipe->qh.qtd_next, (u32)MAKE_FLATPTR(GET_SEG(SS), tds));
u16 maxpacket = GET_LOWFLAT(pipe->pipe.maxpacket);
int tdpos = 0;
while (datasize) {
struct ehci_qtd *td = &tds[tdpos++ % STACKQTDS];
int ret = ehci_wait_td(pipe, td, 5000);
if (ret)
return -1;
struct ehci_qtd *nexttd_fl = MAKE_FLATPTR(GET_SEG(SS)
, &tds[tdpos % STACKQTDS]);
int transfer = fillTDbuffer(td, maxpacket, data, datasize);
td->qtd_next = (transfer==datasize ? EHCI_PTR_TERM : (u32)nexttd_fl);
td->alt_next = EHCI_PTR_TERM;
barrier();
td->token = (ehci_explen(transfer) | QTD_STS_ACTIVE
| (dir ? QTD_PID_IN : QTD_PID_OUT) | ehci_maxerr(3));
data += transfer;
datasize -= transfer;
}
int i;
for (i=0; i<STACKQTDS; i++) {
struct ehci_qtd *td = &tds[tdpos++ % STACKQTDS];
int ret = ehci_wait_td(pipe, td, 5000);
if (ret)
return -1;
}
return 0;
}
int
ehci_poll_intr(struct usb_pipe *p, void *data)
{
ASSERT16();
if (! CONFIG_USB_EHCI)
return -1;
struct ehci_pipe *pipe = container_of(p, struct ehci_pipe, pipe);
struct ehci_qtd *td = GET_LOWFLAT(pipe->next_td);
u32 token = GET_LOWFLAT(td->token);
if (token & QTD_STS_ACTIVE)
// No intrs found.
return -1;
// XXX - check for errors.
// Copy data.
int maxpacket = GET_LOWFLAT(pipe->pipe.maxpacket);
int pos = td - GET_LOWFLAT(pipe->tds);
void *tddata = GET_LOWFLAT(pipe->data) + maxpacket * pos;
memcpy_far(GET_SEG(SS), data, SEG_LOW, LOWFLAT2LOW(tddata), maxpacket);
// Reenable this td.
struct ehci_qtd *next = (void*)(GET_LOWFLAT(td->qtd_next) & ~EHCI_PTR_BITS);
SET_LOWFLAT(pipe->next_td, next);
SET_LOWFLAT(td->buf[0], (u32)tddata);
barrier();
SET_LOWFLAT(td->token, (ehci_explen(maxpacket) | QTD_STS_ACTIVE
| QTD_PID_IN | ehci_maxerr(3)));
return 0;
}