From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754067AbcIDPvR (ORCPT ); Sun, 4 Sep 2016 11:51:17 -0400 Received: from mga07.intel.com ([134.134.136.100]:13739 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753118AbcIDPvQ (ORCPT ); Sun, 4 Sep 2016 11:51:16 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,281,1470726000"; d="scan'208";a="4965196" From: Chen Yu To: Lee Jones Cc: linux-kernel@vger.kernel.org, Chen Yu , Andy Shevchenko , Mika Westerberg , "Rafael J . Wysocki" Subject: [PATCH][RFC] mfd: intel-lpss: Avoid resuming runtime-suspended lpss unnecessarily Date: Sun, 4 Sep 2016 23:58:58 +0800 Message-Id: <1473004738-6067-1-git-send-email-yu.c.chen@intel.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We have report that the intel_lpss_prepare() takes too much time during suspend, and this is because we first resume the devices from runtime suspend by resume_lpss_device(), to make sure they are in proper state before system suspend, which takes 100ms for each LPSS devices(PCI power state from D3_cold to D0). And since resume_lpss_device() resumes the devices synchronously, we might get huge latency if we have many LPSS devices. So first try is to use pm_request_resume() instead, to make the runtime resume process asynchronously. Unfortunately the asynchronous runtime resume relies on pm_wq, which is freezed at early stage. So we choose another method, that is to avoid resuming runtime-suspended devices, if they are already runtime suspended. This is safe because for LPSS driver, the runtime suspend and system suspend are of the same hook - i.e., intel_lpss_suspend(). And moreover, this device is neither runtime wakeup source nor system wakeup source. Cc: Andy Shevchenko Cc: Mika Westerberg Cc: Rafael J. Wysocki Signed-off-by: Chen Yu --- drivers/mfd/intel-lpss.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c index 41b1138..6dcc9a0 100644 --- a/drivers/mfd/intel-lpss.c +++ b/drivers/mfd/intel-lpss.c @@ -485,6 +485,15 @@ static int resume_lpss_device(struct device *dev, void *data) int intel_lpss_prepare(struct device *dev) { /* + * This is safe because: + * 1. The runtime suspend and system suspend + * are of the same hook. + * 2. This device is neither runtime wakeup source + * nor system wakeup source. + */ + if (pm_runtime_status_suspended(dev)) + return 1; + /* * Resume both child devices before entering system sleep. This * ensures that they are in proper state before they get suspended. */ -- 2.7.4