On Tue, 27 Jan 2009, Saito.Koichiro wrote:
> I think that it is difficult to put out a well-grounded
> numerical value even if I thinks any further. If we usually
> use it, I guess that low probability of unplugging a device
> while accessing to a device. Because it is thought that CPU
> is not completely occupied only with retrying, I think that
> no problem. I want to finish the modification by the
> retrying of 32 times. I changed to 32 from 255.
> How do you think?
I'm using 32 now.
> >You did not understand my question. What happens if ehci_hcd is
> >_loaded_ and the device is running at full speed or low speed because
> >it is a USB-1.1 device plugged into a high-speed hub?
I tried doing this test. It worked okay. Sometimes there were 2
retries instead of just 1.
I also changed the patch to avoid retrying qtd's for an unlinked URB.
That should help reduce the overhead when a device is unplugged.
The current patch is below. I think it's ready to be submitted. Do
you agree?
Alan Stern
Index: usb-2.6/drivers/usb/host/ehci-q.c
===================================================================
--- usb-2.6.orig/drivers/usb/host/ehci-q.c
+++ usb-2.6/drivers/usb/host/ehci-q.c
@@ -333,12 +333,40 @@ qh_completions (struct ehci_hcd *ehci, s
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_h
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 */
}
Index: usb-2.6/drivers/usb/host/ehci.h
===================================================================
--- usb-2.6.orig/drivers/usb/host/ehci.h
+++ usb-2.6/drivers/usb/host/ehci.h
@@ -370,6 +370,9 @@ 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 */
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
