aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/usb/host/ehci.h
diff options
context:
space:
mode:
authorDavid Brownell <dbrownell@users.sourceforge.net>2008-06-03 22:21:55 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2008-07-21 15:16:27 -0700
commitb963801164618e25fbdc0cd452ce49c3628b46c8 (patch)
tree149c888f19921f356607c8d7a1c1001e148450ba /drivers/usb/host/ehci.h
parent38f3ad5e7463d4dd490a8081a5f3f9f2dec7ecd6 (diff)
downloadmrst-s0i3-test-b963801164618e25fbdc0cd452ce49c3628b46c8.tar.gz
mrst-s0i3-test-b963801164618e25fbdc0cd452ce49c3628b46c8.tar.xz
mrst-s0i3-test-b963801164618e25fbdc0cd452ce49c3628b46c8.zip
USB: ehci-hcd unlink speedups
This patch fixes some performance bugs observed with some workloads when unlinking EHCI queue header (QH) descriptors from the async ring (control/bulk schedule). The mechanism intended to defer unlinking an empty QH (so there is no penalty in common cases where it's quickly reused) was not working as intended. Sometimes the unlink was scheduled: - too quickly ... which can be a *strong* negative effect, since that QH becomes unavailable for immediate re-use; - too slowly ... wasting DMA cycles, usually a minor issue except for increased bus contention and power usage; Plus there was an extreme case of "too slowly": a logical error in the IAA watchdog-timer conversion meant that sometimes the unlink never got scheduled. The fix replaces a simple counter with a timestamp derived from the controller's 8 KHz microframe counter, and adjusts the timer usage for some issues associated with HZ being less than 8K. (Based on a patch originally by Alan Stern, and good troubleshooting from Leonid.) Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: Alan Stern <stern@rowland.harvard.edu> Cc: Leonid <leonidv11@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/host/ehci.h')
-rw-r--r--drivers/usb/host/ehci.h5
1 files changed, 4 insertions, 1 deletions
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index 90245fd8bac..5799298364f 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -198,7 +198,10 @@ timer_action (struct ehci_hcd *ehci, enum ehci_timer_action action)
break;
// case TIMER_ASYNC_SHRINK:
default:
- t = EHCI_SHRINK_JIFFIES;
+ /* add a jiffie since we synch against the
+ * 8 KHz uframe counter.
+ */
+ t = DIV_ROUND_UP(EHCI_SHRINK_FRAMES * HZ, 1000) + 1;
break;
}
mod_timer(&ehci->watchdog, t + jiffies);