From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933213AbcILPPL (ORCPT ); Mon, 12 Sep 2016 11:15:11 -0400 Received: from mail-lf0-f52.google.com ([209.85.215.52]:34398 "EHLO mail-lf0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933127AbcILPPJ (ORCPT ); Mon, 12 Sep 2016 11:15:09 -0400 Date: Mon, 12 Sep 2016 16:17:04 +0100 From: Lee Jones To: Chen Yu Cc: linux-kernel@vger.kernel.org, Andy Shevchenko , Mika Westerberg , "Rafael J . Wysocki" Subject: Re: [PATCH][RFC] mfd: intel-lpss: Avoid resuming runtime-suspended lpss unnecessarily Message-ID: <20160912151704.GH9789@dell> References: <1473004738-6067-1-git-send-email-yu.c.chen@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1473004738-6067-1-git-send-email-yu.c.chen@intel.com> User-Agent: Mutt/1.6.2 (2016-07-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 04 Sep 2016, Chen Yu wrote: > 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; What's '1'? > + /* > * Resume both child devices before entering system sleep. This > * ensures that they are in proper state before they get suspended. > */ -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog