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authorMing Lei <ming.lei@canonical.com>2013-07-03 22:53:10 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-08-12 11:43:48 -0700
commit9118f9eb4f1e97a135de3f78853c411befcf9775 (patch)
tree1db640132f3a1dfbffbbe74ca2382c3239de8d90 /drivers/usb/host/ehci-timer.c
parent35371e4fbc3e1863a6e7a79b8c17c25cc96a1380 (diff)
downloadlinux-stericsson-9118f9eb4f1e97a135de3f78853c411befcf9775.tar.gz
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-timer.c')
-rw-r--r--drivers/usb/host/ehci-timer.c34
1 files changed, 33 insertions, 1 deletions
diff --git a/drivers/usb/host/ehci-timer.c b/drivers/usb/host/ehci-timer.c
index 11e5b32f73e9..424ac5d83714 100644
--- a/drivers/usb/host/ehci-timer.c
+++ b/drivers/usb/host/ehci-timer.c
@@ -72,6 +72,7 @@ static unsigned event_delays_ns[] = {
1 * NSEC_PER_MSEC, /* EHCI_HRTIMER_POLL_DEAD */
1125 * NSEC_PER_USEC, /* EHCI_HRTIMER_UNLINK_INTR */
2 * NSEC_PER_MSEC, /* EHCI_HRTIMER_FREE_ITDS */
+ 5 * NSEC_PER_MSEC, /* EHCI_HRTIMER_START_UNLINK_INTR */
6 * NSEC_PER_MSEC, /* EHCI_HRTIMER_ASYNC_UNLINKS */
10 * NSEC_PER_MSEC, /* EHCI_HRTIMER_IAA_WATCHDOG */
10 * NSEC_PER_MSEC, /* EHCI_HRTIMER_DISABLE_PERIODIC */
@@ -215,6 +216,36 @@ static void ehci_handle_controller_death(struct ehci_hcd *ehci)
/* Not in process context, so don't try to reset the controller */
}
+/* start to unlink interrupt QHs */
+static void ehci_handle_start_intr_unlinks(struct ehci_hcd *ehci)
+{
+ bool stopped = (ehci->rh_state < EHCI_RH_RUNNING);
+
+ /*
+ * Process all the QHs on the intr_unlink list that were added
+ * before the current unlink cycle began. The list is in
+ * temporal order, so stop when we reach the first entry in the
+ * current cycle. But if the root hub isn't running then
+ * process all the QHs on the list.
+ */
+ while (!list_empty(&ehci->intr_unlink_wait)) {
+ struct ehci_qh *qh;
+
+ qh = list_first_entry(&ehci->intr_unlink_wait,
+ struct ehci_qh, unlink_node);
+ if (!stopped && (qh->unlink_cycle ==
+ ehci->intr_unlink_wait_cycle))
+ break;
+ list_del_init(&qh->unlink_node);
+ start_unlink_intr(ehci, qh);
+ }
+
+ /* Handle remaining entries later */
+ if (!list_empty(&ehci->intr_unlink_wait)) {
+ ehci_enable_event(ehci, EHCI_HRTIMER_START_UNLINK_INTR, true);
+ ++ehci->intr_unlink_wait_cycle;
+ }
+}
/* Handle unlinked interrupt QHs once they are gone from the hardware */
static void ehci_handle_intr_unlinks(struct ehci_hcd *ehci)
@@ -236,7 +267,7 @@ static void ehci_handle_intr_unlinks(struct ehci_hcd *ehci)
unlink_node);
if (!stopped && qh->unlink_cycle == ehci->intr_unlink_cycle)
break;
- list_del(&qh->unlink_node);
+ list_del_init(&qh->unlink_node);
end_unlink_intr(ehci, qh);
}
@@ -363,6 +394,7 @@ static void (*event_handlers[])(struct ehci_hcd *) = {
ehci_handle_controller_death, /* EHCI_HRTIMER_POLL_DEAD */
ehci_handle_intr_unlinks, /* EHCI_HRTIMER_UNLINK_INTR */
end_free_itds, /* EHCI_HRTIMER_FREE_ITDS */
+ ehci_handle_start_intr_unlinks, /* EHCI_HRTIMER_START_UNLINK_INTR */
unlink_empty_async, /* EHCI_HRTIMER_ASYNC_UNLINKS */
ehci_iaa_watchdog, /* EHCI_HRTIMER_IAA_WATCHDOG */
ehci_disable_PSE, /* EHCI_HRTIMER_DISABLE_PERIODIC */