github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-06-07 22:14:04 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

UPSTREAM: xhci: flush endpoint start to reduce race risk with stop endpoint command.

Browse Source 
Stop endpoint command fails with "context state error" if the endpoint is
already stopped.

This case was observed when a previous URB cancel had just completed and
rang the doorbell to restart the ring, when a new URB cancel queued a stop
endpoint command.
>From xHC hardware pov the endpoint had not yet started, so the stop
endpoint command failed with context state error.
Right after this the doorbell ring took effect and ring was restarted.

Interrupt handler saw a stop endpoint command completion event with
"context state error" and discovered that the ring was back up in
running state.

flushing the write reduces these cases in stress testing, but does not
completely remove the issue.

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20210129130044.206855-15-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit b05dadb28f
 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-linus)
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I644d2623fb80819471dbd2a1f43c5d1af176c213
This commit is contained in:
Mathias Nyman 2021-01-29 15:00:31 +02:00 committed by Greg Kroah-Hartman
parent 2a83ae8e16
commit 539a9a70ef
1 changed files with 2 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
drivers/usb/host/xhci-ring.c
View File

@ -429,9 +429,8 @@ void xhci_ring_ep_doorbell(struct xhci_hcd *xhci,
trace_xhci_ring_ep_doorbell(slot_id, DB_VALUE(ep_index, stream_id));
writel(DB_VALUE(ep_index, stream_id), db_addr);
/* The CPU has better things to do at this point than wait for a
* write-posting flush. It'll get there soon enough.
*/
/* flush the write */
readl(db_addr);
}
/* Ring the doorbell for any rings with pending URBs */