New patch to review for coreboot: 31887a0 libpayload: Add interrupt-queue underrun recovery to EHCI

[Nico Huber]

Nico Huber ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/1123

-gerrit

commit 31887a042a68fb05a6718183aaa1eded4ea3e4a1
Author: Nico Huber 
Date:   Thu Jun 14 13:08:36 2012 +0200

libpayload: Add interrupt-queue underrun recovery to EHCI

If the queue of an interrupt transfer runs out, we have to reset
    the queue head. This also introduces the use of a spare transfer
    descriptor (TD) in interrupt queues, which assures, that a processed
    TD  won't be reused until the host controller has written it back
    from his overlay.

Change-Id: Id0eeb2808b77f1c187f164eb34bd66f8f399938b
    Signed-off-by: Nico Huber 
---
 payloads/libpayload/drivers/usb/ehci.c |   41 ++++++++++++++++++++-----------
 1 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/payloads/libpayload/drivers/usb/ehci.c b/payloads/libpayload/drivers/usb/ehci.c
index 9e17571..d99901a 100644
--- a/payloads/libpayload/drivers/usb/ehci.c
+++ b/payloads/libpayload/drivers/usb/ehci.c
@@ -410,6 +410,7 @@ typedef struct {
    volatile ehci_qh_t	qh;
    intr_qtd_t		*head;
    intr_qtd_t		*tail;
+	intr_qtd_t		*spare;
    u8			*data;
    endpoint_t		*endp;
    int			reqsize;
@@ -466,7 +467,11 @@ static void *ehci_create_intr_queue(

intr_queue_t *const intrq =
    	(intr_queue_t *)memalign(32, sizeof(intr_queue_t));
-	u8 *data = (u8 *)malloc(reqsize * reqcount);
+	/*
+	 * reqcount data chunks
+	 * plus one more spare, which we'll leave out of queue
+	 */
+	u8 *data = (u8 *)malloc(reqsize * (reqcount + 1));
    if (!intrq || !data)
    	fatal("Not enough memory to create USB interrupt queue.\n");
    intrq->data = data;
@@ -490,6 +495,10 @@ static void *ehci_create_intr_queue(
    }
    intrq->tail = cur_td;

+	/* create spare qTD */
+	intrq->spare = (intr_qtd_t *)memalign(32, sizeof(intr_qtd_t));
+	fill_intr_queue_td(intrq, intrq->spare, data);
+
    /* initialize QH */
    const int endp = ep->endpoint & 0xf;
    memset(&intrq->qh, 0, sizeof(intrq->qh));
@@ -558,6 +567,7 @@ static void ehci_destroy_intr_queue(endpoint_t *const ep, void *const queue)
    	/* free current interrupt qTD */
    	free(to_free);
    }
+	free(intrq->spare);
    free(intrq->data);
    free(intrq);
 }
@@ -569,9 +579,7 @@ static u8 *ehci_poll_intr_queue(void *const queue)
    u8 *ret = NULL;

/* process if head qTD is inactive AND QH has been moved forward */
-	if (!(intrq->head->td.token & QTD_ACTIVE) &&
-			(intrq->qh.current_td_ptr !=
-			 virt_to_phys(&intrq->head->td))) {
+	if (!(intrq->head->td.token & QTD_ACTIVE)) {
    	if (!(intrq->head->td.token & QTD_STATUS_MASK))
    		ret = intrq->head->data;
    	else
@@ -579,18 +587,21 @@ static u8 *ehci_poll_intr_queue(void *const queue)
    			"status == 0x%02x\n",
    			intrq->head->td.token & QTD_STATUS_MASK);

-		/* save and advance our head ptr */
-		intr_qtd_t *const new_td = intrq->head;
-		intrq->head = intrq->head->next;
-
-		/* reuse executed qTD */
-		fill_intr_queue_td(intrq, new_td, new_td->data);
-
-		/* at last insert reused qTD at the
-		 * end and advance our tail ptr */
-		intrq->tail->td.next_qtd = virt_to_phys(&new_td->td);
-		intrq->tail->next = new_td;
+		/* insert spare qTD at the end and advance our tail ptr */
+		fill_intr_queue_td(intrq, intrq->spare, intrq->spare->data);
+		intrq->tail->td.next_qtd = virt_to_phys(&intrq->spare->td);
+		intrq->tail->next = intrq->spare;
    	intrq->tail = intrq->tail->next;
+
+		/* reuse executed qTD as spare one and advance our head ptr */
+		intrq->spare = intrq->head;
+		intrq->head = intrq->head->next;
+	}
+	/* reset queue if we fully processed it after underrun */
+	else if (intrq->qh.td.next_qtd & QTD_TERMINATE) {
+		debug("resetting underrun ehci interrupt queue.\n");
+		memset(&intrq->qh.td, 0, sizeof(intrq->qh.td));
+		intrq->qh.td.next_qtd = virt_to_phys(&intrq->head->td);
    }
    return ret;
 }