From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753987AbYIYJ2Z (ORCPT ); Thu, 25 Sep 2008 05:28:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752838AbYIYJ2R (ORCPT ); Thu, 25 Sep 2008 05:28:17 -0400 Received: from mga11.intel.com ([192.55.52.93]:39858 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752231AbYIYJ2Q (ORCPT ); Thu, 25 Sep 2008 05:28:16 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.33,307,1220252400"; d="scan'208";a="620169874" Subject: [PATCH] USB: improve ehci_watchdog's side effect in CPU power management From: Yi Yang Reply-To: yi.y.yang@intel.com To: linux-kernel@vger.kernel.org Cc: dbrownell@users.sourceforge.net, gregkh@suse.de, akpm@linux-foundation.org Content-Type: text/plain Organization: Intel Date: Thu, 25 Sep 2008 17:25:44 +0800 Message-Id: <1222334744.9267.41.camel@yangyi-dev> Mime-Version: 1.0 X-Mailer: Evolution 2.22.1 (2.22.1-2.fc9) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- ehci.h | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h index 5799298..9d530d9 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)); } }