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USB: EHCI: slow down ITD reuse

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Currently ITDs are immediately recycled whenever their URB completes.
However, EHCI hardware can sometimes remember some ITD state.  This
means that when the ITD is reused before end-of-frame it may sometimes
cause the hardware to reference bogus state.

This patch defers reusing such ITDs by moving them into a new ehci member
cached_itd_list. ITDs resting in cached_itd_list are moved back into their
stream's free_list once scan_periodic() detects that the active frame has
elapsed.

This makes the snd_usb_us122l driver (in kernel since .28) work right
when it's hooked up through EHCI.

[ dbrownell@users.sourceforge.net: comment fixups ]

Signed-off-by: Karsten Wiese <fzu@wemgehoertderstaat.de>
Tested-by: Philippe Carriere <philippe-f.carriere@wanadoo.fr>
Tested-by: Federico Briata <federicobriata@gmail.com>
Cc: stable <stable@kernel.org>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Karsten Wiese
2009-02-08 16:07:58 -08:00
committed by Greg Kroah-Hartman
parent 9a6e184c80
commit 9aa09d2f8f
4 changed files with 57 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

56
drivers/usb/host/ehci-sched.c
View File

@@ -1004,7 +1004,8 @@ iso_stream_put(struct ehci_hcd *ehci, struct ehci_iso_stream *stream)
is_in = (stream->bEndpointAddress & USB_DIR_IN) ? 0x10 : 0;
stream->bEndpointAddress &= 0x0f;
stream->ep->hcpriv = NULL;
if (stream->ep)
stream->ep->hcpriv = NULL;
if (stream->rescheduled) {
ehci_info (ehci, "ep%d%s-iso rescheduled "
@@ -1653,14 +1654,28 @@ itd_complete (
(stream->bEndpointAddress & USB_DIR_IN) ? "in" : "out");
}
iso_stream_put (ehci, stream);
/* OK to recycle this ITD now that its completion callback ran. */
done:
usb_put_urb(urb);
itd->urb = NULL;
itd->stream = NULL;
list_move(&itd->itd_list, &stream->free_list);
iso_stream_put(ehci, stream);
if (ehci->clock_frame != itd->frame || itd->index[7] != -1) {
/* OK to recycle this ITD now. */
itd->stream = NULL;
list_move(&itd->itd_list, &stream->free_list);
iso_stream_put(ehci, stream);
} else {
/* HW might remember this ITD, so we can't recycle it yet.
* Move it to a safe place until a new frame starts.
*/
list_move(&itd->itd_list, &ehci->cached_itd_list);
if (stream->refcount == 2) {
/* If iso_stream_put() were called here, stream
* would be freed. Instead, just prevent reuse.
*/
stream->ep->hcpriv = NULL;
stream->ep = NULL;
}
}
return retval;
}
@@ -2101,6 +2116,20 @@ done:
/*-------------------------------------------------------------------------*/
static void free_cached_itd_list(struct ehci_hcd *ehci)
{
struct ehci_itd *itd, *n;
list_for_each_entry_safe(itd, n, &ehci->cached_itd_list, itd_list) {
struct ehci_iso_stream *stream = itd->stream;
itd->stream = NULL;
list_move(&itd->itd_list, &stream->free_list);
iso_stream_put(ehci, stream);
}
}
/*-------------------------------------------------------------------------*/
static void
scan_periodic (struct ehci_hcd *ehci)
{
@@ -2115,10 +2144,17 @@ scan_periodic (struct ehci_hcd *ehci)
* Touches as few pages as possible: cache-friendly.
*/
now_uframe = ehci->next_uframe;
if (HC_IS_RUNNING (ehci_to_hcd(ehci)->state))
if (HC_IS_RUNNING(ehci_to_hcd(ehci)->state)) {
clock = ehci_readl(ehci, &ehci->regs->frame_index);
else
clock_frame = (clock >> 3) % ehci->periodic_size;
} else {
clock = now_uframe + mod - 1;
clock_frame = -1;
}
if (ehci->clock_frame != clock_frame) {
free_cached_itd_list(ehci);
ehci->clock_frame = clock_frame;
}
clock %= mod;
clock_frame = clock >> 3;
@@ -2277,6 +2313,10 @@ restart:
/* rescan the rest of this frame, then ... */
clock = now;
clock_frame = clock >> 3;
if (ehci->clock_frame != clock_frame) {
free_cached_itd_list(ehci);
ehci->clock_frame = clock_frame;
}
} else {
now_uframe++;
now_uframe %= mod;