USB: EHCI: stagger frames for interrupt transfers
This patch (as1243) tries to improve ehci-hcd's scheduling of
interrupt transfers. Instead of trying to cram all transfers with the
same period into the same frame, the new code will spread the
transfers out among lots of different frames. This should reduce the
periodic schedule load in any one frame -- some host controllers have
trouble when there's too much work to do.
A more thorough approach would stagger the uframe values as well. But
this is enough to make a big improvement.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Dwayne Fontenot <dwayne.fontenot@att.net>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 556d0ec..9d1babc 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -760,8 +760,10 @@
if (status) {
/* "normal" case, uframing flexible except with splits */
if (qh->period) {
- frame = qh->period - 1;
- do {
+ int i;
+
+ for (i = qh->period; status && i > 0; --i) {
+ frame = ++ehci->random_frame % qh->period;
for (uframe = 0; uframe < 8; uframe++) {
status = check_intr_schedule (ehci,
frame, uframe, qh,
@@ -769,7 +771,7 @@
if (status == 0)
break;
}
- } while (status && frame--);
+ }
/* qh->period == 0 means every uframe */
} else {
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index 6cff195..90ad339 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -116,6 +116,7 @@
struct timer_list watchdog;
unsigned long actions;
unsigned stamp;
+ unsigned random_frame;
unsigned long next_statechange;
u32 command;