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authorAlan Stern <stern@rowland.harvard.edu>2009-02-10 10:16:58 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2009-03-24 16:20:31 -0700
commita2c2706e1043c17139c2dafd171c4a5cf008ef7e (patch)
tree59d6519004eb562ebee5df5f1a4394290dec16ff
parent1f4159c1620f74377e26d8a569d10ca5907ef475 (diff)
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USB: EHCI: add software retry for transaction errors
This patch (as1204) adds a software retry mechanism to ehci-hcd. It gets invoked when the driver encounters transaction errors on an asynchronous endpoint. On many systems, hardware deficiencies cause such errors to occur if one device is unplugged while the host is communicating with another device. With the patch, the failed transactions are retried and generally succeed the second or third time through. This is based on code originally written by Koichiro Saito. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Tested by: Koichiro Saito <Saito.Koichiro@adniss.jp> CC: David Brownell <david-b@pacbell.net> Cc: stable <stable@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/usb/host/ehci-q.c32
-rw-r--r--drivers/usb/host/ehci.h3
2 files changed, 35 insertions, 0 deletions
diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index ecc9b66c03c..01132ac74eb 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -333,12 +333,40 @@ qh_completions (struct ehci_hcd *ehci, struct ehci_qh *qh)
token = hc32_to_cpu(ehci, qtd->hw_token);
/* always clean up qtds the hc de-activated */
+ retry_xacterr:
if ((token & QTD_STS_ACTIVE) == 0) {
/* on STALL, error, and short reads this urb must
* complete and all its qtds must be recycled.
*/
if ((token & QTD_STS_HALT) != 0) {
+
+ /* retry transaction errors until we
+ * reach the software xacterr limit
+ */
+ if ((token & QTD_STS_XACT) &&
+ QTD_CERR(token) == 0 &&
+ --qh->xacterrs > 0 &&
+ !urb->unlinked) {
+ ehci_dbg(ehci,
+ "detected XactErr len %d/%d retry %d\n",
+ qtd->length - QTD_LENGTH(token), qtd->length,
+ QH_XACTERR_MAX - qh->xacterrs);
+
+ /* reset the token in the qtd and the
+ * qh overlay (which still contains
+ * the qtd) so that we pick up from
+ * where we left off
+ */
+ token &= ~QTD_STS_HALT;
+ token |= QTD_STS_ACTIVE |
+ (EHCI_TUNE_CERR << 10);
+ qtd->hw_token = cpu_to_hc32(ehci,
+ token);
+ wmb();
+ qh->hw_token = cpu_to_hc32(ehci, token);
+ goto retry_xacterr;
+ }
stopped = 1;
/* magic dummy for some short reads; qh won't advance.
@@ -421,6 +449,9 @@ halt:
/* remove qtd; it's recycled after possible urb completion */
list_del (&qtd->qtd_list);
last = qtd;
+
+ /* reinit the xacterr counter for the next qtd */
+ qh->xacterrs = QH_XACTERR_MAX;
}
/* last urb's completion might still need calling */
@@ -862,6 +893,7 @@ static void qh_link_async (struct ehci_hcd *ehci, struct ehci_qh *qh)
head->qh_next.qh = qh;
head->hw_next = dma;
+ qh->xacterrs = QH_XACTERR_MAX;
qh->qh_state = QH_STATE_LINKED;
/* qtd completions reported later by interrupt */
}
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index 0042deb671d..9aba560fd56 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -342,6 +342,9 @@ struct ehci_qh {
#define QH_STATE_UNLINK_WAIT 4 /* LINKED and on reclaim q */
#define QH_STATE_COMPLETING 5 /* don't touch token.HALT */
+ u8 xacterrs; /* XactErr retry counter */
+#define QH_XACTERR_MAX 32 /* XactErr retry limit */
+
/* periodic schedule info */
u8 usecs; /* intr bandwidth */
u8 gap_uf; /* uframes split/csplit gap */