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authorYi Yang <yi.y.yang@intel.com>2008-09-25 13:25:44 +0400
committerGreg Kroah-Hartman <gregkh@suse.de>2008-10-18 01:41:02 +0400
commitf0d781d59cb621e1795d510039df973d0f8b23fc (patch)
treebc1a60dac25eef26e22d346ebf08496b7702ac94
parente58dcebcd83b5902411e747ee7807219dee6bcf2 (diff)
downloadlinux-f0d781d59cb621e1795d510039df973d0f8b23fc.tar.xz
USB: improve ehci_watchdog's side effect in CPU power management
ehci_watchdog will wake up CPU very frequently so that CPU stays at C3 very short, average residence time is about 50 ms on Aspire One, but we expect it should be about 1 second or more, so this kind of periodic timer is very bad for power saving. We can't remove this timer because of some bad USB controller chipset, but at least we should reduce its side effect to as possible as low. This patch can make CPU stay at C3 longer, average residence time is about twice as long as original. Please consider to apply it, thanks Signed-off-by: Yi Yang <yi.y.yang@intel.com> Cc: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/usb/host/ehci.h12
1 files changed, 7 insertions, 5 deletions
diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
index fb1770d6e200..a6fd550b6903 100644
--- a/drivers/usb/host/ehci.h
+++ b/drivers/usb/host/ehci.h
@@ -181,14 +181,16 @@ timer_action (struct ehci_hcd *ehci, enum ehci_timer_action action)
* the async ring; just the I/O watchdog. Note that if a
* SHRINK were pending, OFF would never be requested.
*/
- if (timer_pending(&ehci->watchdog)
- && ((BIT(TIMER_ASYNC_SHRINK) | BIT(TIMER_ASYNC_OFF))
- & ehci->actions))
- return;
+ enum ehci_timer_action oldactions = ehci->actions;
if (!test_and_set_bit (action, &ehci->actions)) {
unsigned long t;
+ if (timer_pending(&ehci->watchdog)
+ && ((BIT(TIMER_ASYNC_SHRINK) | BIT(TIMER_ASYNC_OFF))
+ & oldactions))
+ return;
+
switch (action) {
case TIMER_IO_WATCHDOG:
t = EHCI_IO_JIFFIES;
@@ -204,7 +206,7 @@ timer_action (struct ehci_hcd *ehci, enum ehci_timer_action action)
t = DIV_ROUND_UP(EHCI_SHRINK_FRAMES * HZ, 1000) + 1;
break;
}
- mod_timer(&ehci->watchdog, t + jiffies);
+ mod_timer(&ehci->watchdog, round_jiffies(t + jiffies));
}
}