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libpayload: xhci: Use Event Data TRBs for transfer event generation 

The current XHCI code only sets IOC on the last TRB of a TD, and
doesn't set ISP anywhere. On my Synopsys DesignWare3 controller, this
won't generate an event at all when we have a short transfer that is not
on the last TRB of a TD, resulting in event ring desync and everyone
having a bad time. However, just setting ISP on other TRBs doesn't
really make for a nice solution: we then need to do ugly special casing
to fish out the spurious second transfer event you get for short
packets, and we still need a way to figure out how many bytes were
transferred. Since the Short Packet transfer event only reports
untransferred bytes for the current TRB, we would have to manually walk
the rest of the unprocessed TRB chain and add up the bytes. Check out
U-Boot and the Linux kernel to see how complicated this looks in
practice.

Now what if we had a way to just tell the HC "I want an event at exactly
*this* point in the TD, I want it to have the right completion code for
the whole TD, and to contain the exact number of bytes written"? Enter
the Event Data TRB: this little gizmo really does pretty much exactly
what any sane XHCI driver would want, and I have no idea why it isn't
used more often. It solves both the short packet event generation and
counting the transferred bytes without requiring any special magic in
software.

Change-Id: Idab412d61edf30655ec69c80066bfffd80290403
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/170980
Reviewed-by: Stefan Reinauer <reinauer@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
(cherry picked from commit e512c8bcaa5b8e05cae3b9d04cd4947298de999d)
Signed-off-by: Isaac Christensen <isaac.christensen@se-eng.com>
Reviewed-on: http://review.coreboot.org/6516
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
This commit is contained in:
Julius Werner 2013-09-27 12:45:11 -07:00 committed by Isaac Christensen
parent 20e2f3c6e4
commit 83da50173c
2 changed files with 13 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
payloads/libpayload/drivers/usb/xhci.c
View File

@ -551,6 +551,7 @@ xhci_enqueue_td(transfer_ring_t *const tr, const int ep, const size_t mps,
trb->ptr_low = virt_to_phys(cur_start);
TRB_SET(TL, trb, cur_length);
TRB_SET(TDS, trb, packets);
TRB_SET(CH, trb, 1);
/* Check for first, data stage TRB */
if (!trb_count && ep == 1) {
@ -560,17 +561,19 @@ xhci_enqueue_td(transfer_ring_t *const tr, const int ep, const size_t mps,
TRB_SET(TT, trb, TRB_NORMAL);
}
/* Check for last TRB */
if (!length)
TRB_SET(IOC, trb, 1);
else
TRB_SET(CH, trb, 1);
xhci_enqueue_trb(tr);
cur_start += cur_length;
++trb_count;
}
trb = tr->cur;
xhci_clear_trb(trb, tr->pcs);
trb->ptr_low = virt_to_phys(trb); /* for easier debugging only */
TRB_SET(TT, trb, TRB_EVENT_DATA);
TRB_SET(IOC, trb, 1);
xhci_enqueue_trb(tr);
}
static int
@ -583,7 +586,7 @@ xhci_control(usbdev_t *const dev, const direction_t dir,
transfer_ring_t *const tr = di->transfer_rings[1];
const size_t off = (size_t)data & 0xffff;
if ((off + dalen) > ((TRANSFER_RING_SIZE - 3) << 16)) {
if ((off + dalen) > ((TRANSFER_RING_SIZE - 4) << 16)) {
xhci_debug("Unsupported transfer size\n");
return 1;
}
@ -670,7 +673,7 @@ xhci_bulk(endpoint_t *const ep,
transfer_ring_t *const tr = di->transfer_rings[ep_id];
const size_t off = (size_t)data & 0xffff;
if ((off + size) > ((TRANSFER_RING_SIZE - 1) << 16)) {
if ((off + size) > ((TRANSFER_RING_SIZE - 2) << 16)) {
xhci_debug("Unsupported transfer size\n");
return 1;
}

3
payloads/libpayload/drivers/usb/xhci_private.h
View File

@ -65,7 +65,7 @@ enum { XHCI_FULL_SPEED = 1, XHCI_LOW_SPEED = 2, XHCI_HIGH_SPEED = 3, XHCI_SUPER_
enum {
TRB_NORMAL = 1,
TRB_SETUP_STAGE = 2, TRB_DATA_STAGE = 3, TRB_STATUS_STAGE = 4,
TRB_LINK = 6,
TRB_LINK = 6, TRB_EVENT_DATA = 7,
TRB_CMD_ENABLE_SLOT = 9, TRB_CMD_DISABLE_SLOT = 10, TRB_CMD_ADDRESS_DEV = 11,
TRB_CMD_CONFIGURE_EP = 12, TRB_CMD_EVAL_CTX = 13, TRB_CMD_RESET_EP = 14,
TRB_CMD_STOP_EP = 15, TRB_CMD_SET_TR_DQ = 16, TRB_CMD_NOOP = 23,
@ -150,6 +150,7 @@ typedef struct {
u8 adv;
} event_ring_t;
/* Never raise this above 256 to prevent transfer event length overflow! */
#define TRANSFER_RING_SIZE 32
typedef struct {
trb_t *ring;