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libpayload: ehci: Prevent some race conditions 

Prevent race conditions, when an interrupt-queue underrun occurred and
the controller is currently working on our queue head or a transfer is
still in progress.

Change-Id: Ia14f80a08071306ee5d1349780be081bfacb206a
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: http://review.coreboot.org/1902
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
Tested-by: build bot (Jenkins)
This commit is contained in:
Nico Huber 2012-11-22 11:14:03 +01:00 committed by Patrick Georgi
parent b2db28babe
commit af169f4dd5
1 changed files with 7 additions and 1 deletions
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8
payloads/libpayload/drivers/usb/ehci.c
View File

@ -626,8 +626,14 @@ static u8 *ehci_poll_intr_queue(void *const queue)
intrq->head = intrq->head->next;
}
/* reset queue if we fully processed it after underrun */
else if (intrq->qh.td.next_qtd & QTD_TERMINATE) {
else if ((intrq->qh.td.next_qtd & QTD_TERMINATE) &&
/* to prevent race conditions:
not our head and not active */
(intrq->qh.current_td_ptr !=
virt_to_phys(&intrq->head->td)) &&
!(intrq->qh.td.token & QTD_ACTIVE)) {
usb_debug("resetting underrun ehci interrupt queue.\n");
intrq->qh.current_td_ptr = 0;
memset((void *)&intrq->qh.td, 0, sizeof(intrq->qh.td));
intrq->qh.td.next_qtd = virt_to_phys(&intrq->head->td);
}