xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

USB: EHCI: improve interrupt qh unlink

Browse Source 
ehci-hcd currently unlinks an interrupt QH when it becomes empty, that
is, after its last URB completes.  This works well because in almost
all cases, the completion handler for an interrupt URB resubmits the
URB; therefore the QH doesn't become empty and doesn't get unlinked.

When we start using tasklets for URB completion, this scheme won't work
as well.  The resubmission won't occur until the tasklet runs, which
will be some time after the completion is queued with the tasklet.
During that delay, the QH will be empty and so will be unlinked
unnecessarily.

To prevent this problem, this patch adds a 5-ms time delay before empty
interrupt QHs are unlinked.  Most often, during that time the interrupt
URB will be resubmitted and thus we can avoid unlinking the QH.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ming Lei
2013-07-03 22:53:10 +08:00
committed by Greg Kroah-Hartman
parent 35371e4fbc
commit 9118f9eb4f
6 changed files with 84 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/usb/host/ehci-hcd.c
View File

@@ -487,6 +487,7 @@ static int ehci_init(struct usb_hcd *hcd)
ehci->periodic_size = DEFAULT_I_TDPS;
INIT_LIST_HEAD(&ehci->async_unlink);
INIT_LIST_HEAD(&ehci->async_idle);
INIT_LIST_HEAD(&ehci->intr_unlink_wait);
INIT_LIST_HEAD(&ehci->intr_unlink);
INIT_LIST_HEAD(&ehci->intr_qh_list);
INIT_LIST_HEAD(&ehci->cached_itd_list);