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authorAlan Stern <stern@rowland.harvard.edu>2011-05-17 10:40:51 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2011-05-17 11:20:24 -0700
commit1e12c910eed82da6971f1c0421a069c680faba2e (patch)
tree46851229d59c72fa10596f7cecd567918ce348eb /drivers/usb/host
parent2b7aaf503d56216b847c8265421d2a7d9b42df3e (diff)
EHCI: don't rescan interrupt QHs needlessly
This patch (as1466) speeds up processing of ehci-hcd's periodic list. The existing code will pointlessly rescan an interrupt endpoint queue each time it encounters the queue's QH in the periodic list, which can happen quite a few times if the endpoint's period is low. On some embedded systems, this useless overhead can waste so much time that the driver falls hopelessly behind and loses events. The patch introduces a "periodic_stamp" variable, which gets incremented each time scan_periodic() runs and each time the scan advances to a new frame. If the corresponding stamp in an interrupt QH is equal to the current periodic_stamp, we assume the QH has already been scanned and skip over it. Otherwise we scan the QH as usual, and if none of its URBs have completed then we store the current periodic_stamp in the QH's stamp, preventing it from being scanned again. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/host')
-rw-r--r--drivers/usb/host/ehci-q.c1
-rw-r--r--drivers/usb/host/ehci-sched.c14
-rw-r--r--drivers/usb/host/ehci.h1
3 files changed, 12 insertions, 4 deletions
diff --git a/drivers/usb/host/ehci-q.c b/drivers/usb/host/ehci-q.c
index a46d6a1388c9..5d6bc624c961 100644
--- a/drivers/usb/host/ehci-q.c
+++ b/drivers/usb/host/ehci-q.c
@@ -826,6 +826,7 @@ qh_make (
is_input, 0,
hb_mult(maxp) * max_packet(maxp)));
qh->start = NO_FRAME;
+ qh->stamp = ehci->periodic_stamp;
if (urb->dev->speed == USB_SPEED_HIGH) {
qh->c_usecs = 0;
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 1543c838b3d1..a7408d88fda0 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -2287,6 +2287,7 @@ scan_periodic (struct ehci_hcd *ehci)
}
clock &= mod - 1;
clock_frame = clock >> 3;
+ ++ehci->periodic_stamp;
for (;;) {
union ehci_shadow q, *q_p;
@@ -2315,10 +2316,14 @@ restart:
temp.qh = qh_get (q.qh);
type = Q_NEXT_TYPE(ehci, q.qh->hw->hw_next);
q = q.qh->qh_next;
- modified = qh_completions (ehci, temp.qh);
- if (unlikely(list_empty(&temp.qh->qtd_list) ||
- temp.qh->needs_rescan))
- intr_deschedule (ehci, temp.qh);
+ if (temp.qh->stamp != ehci->periodic_stamp) {
+ modified = qh_completions(ehci, temp.qh);
+ if (!modified)
+ temp.qh->stamp = ehci->periodic_stamp;
+ if (unlikely(list_empty(&temp.qh->qtd_list) ||
+ temp.qh->needs_rescan))
+ intr_deschedule(ehci, temp.qh);
+ }
qh_put (temp.qh);
break;
case Q_TYPE_FSTN:
@@ -2460,6 +2465,7 @@ restart:
if (ehci->clock_frame != clock_frame) {
free_cached_lists(ehci);
ehci->clock_frame = clock_frame;
+ ++ehci->periodic_stamp;
}
} else {
now_uframe++;
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index 829213423dea..f68e419cae87 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -118,6 +118,7 @@ struct ehci_hcd { /* one per controller */
struct timer_list watchdog;
unsigned long actions;
unsigned stamp;
+ unsigned periodic_stamp;
unsigned random_frame;
unsigned long next_statechange;
ktime_t last_periodic_enable;