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authorMing Lei <ming.lei@canonical.com>2013-07-03 18:53:10 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-08-12 22:43:48 +0400
commit9118f9eb4f1e97a135de3f78853c411befcf9775 (patch)
tree1db640132f3a1dfbffbbe74ca2382c3239de8d90 /drivers/usb/host/ehci.h
parent35371e4fbc3e1863a6e7a79b8c17c25cc96a1380 (diff)
downloadlinux-9118f9eb4f1e97a135de3f78853c411befcf9775.tar.xz
USB: EHCI: improve interrupt qh unlink
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>
Diffstat (limited to 'drivers/usb/host/ehci.h')
-rw-r--r--drivers/usb/host/ehci.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index 64f9a08e959c..947752015d5d 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -88,6 +88,7 @@ enum ehci_hrtimer_event {
EHCI_HRTIMER_POLL_DEAD, /* Wait for dead controller to stop */
EHCI_HRTIMER_UNLINK_INTR, /* Wait for interrupt QH unlink */
EHCI_HRTIMER_FREE_ITDS, /* Wait for unused iTDs and siTDs */
+ EHCI_HRTIMER_START_UNLINK_INTR, /* Unlink empty interrupt QHs */
EHCI_HRTIMER_ASYNC_UNLINKS, /* Unlink empty async QHs */
EHCI_HRTIMER_IAA_WATCHDOG, /* Handle lost IAA interrupts */
EHCI_HRTIMER_DISABLE_PERIODIC, /* Wait to disable periodic sched */
@@ -143,7 +144,9 @@ struct ehci_hcd { /* one per controller */
unsigned i_thresh; /* uframes HC might cache */
union ehci_shadow *pshadow; /* mirror hw periodic table */
+ struct list_head intr_unlink_wait;
struct list_head intr_unlink;
+ unsigned intr_unlink_wait_cycle;
unsigned intr_unlink_cycle;
unsigned now_frame; /* frame from HC hardware */
unsigned last_iso_frame; /* last frame scanned for iso */