From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756100AbcI0Srv (ORCPT ); Tue, 27 Sep 2016 14:47:51 -0400 Received: from mail-pf0-f170.google.com ([209.85.192.170]:34313 "EHLO mail-pf0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754129AbcI0Sro (ORCPT ); Tue, 27 Sep 2016 14:47:44 -0400 Date: Tue, 27 Sep 2016 19:49:50 +0100 From: Lee Jones To: "Chen, Yu C" Cc: "Wysocki, Rafael J" , "linux-kernel@vger.kernel.org" , Andy Shevchenko , Mika Westerberg Subject: Re: [PATCH][RFC] mfd: intel-lpss: Avoid resuming runtime-suspended lpss unnecessarily Message-ID: <20160927184950.GE21388@dell> References: <1473004738-6067-1-git-send-email-yu.c.chen@intel.com> <20160912151704.GH9789@dell> <20160912154123.GA1986@sharon> <20160913082422.GB22903@dell> <36DF59CE26D8EE47B0655C516E9CE6405E60F6DD@shsmsx102.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <36DF59CE26D8EE47B0655C516E9CE6405E60F6DD@shsmsx102.ccr.corp.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 Tue, 20 Sep 2016, Chen, Yu C wrote: > > -----Original Message----- > > From: Wysocki, Rafael J > > Sent: Tuesday, September 13, 2016 8:16 PM > > To: Lee Jones; Chen, Yu C > > Cc: linux-kernel@vger.kernel.org; Andy Shevchenko; Mika Westerberg > > Subject: Re: [PATCH][RFC] mfd: intel-lpss: Avoid resuming runtime-suspended > > lpss unnecessarily > > > > On 9/13/2016 10:24 AM, Lee Jones wrote: > > > On Mon, 12 Sep 2016, Chen Yu wrote: > > >> On Mon, Sep 12, 2016 at 04:17:04PM +0100, Lee Jones wrote: > > >>> 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'? > > >>> > > >> According to the comment in device_prepare(): > > >> > > >> A positive return value from ->prepare() means "this device appears > > >> to be runtime-suspended and its state is fine, so if it really is > > >> runtime-suspended, you can leave it in that state provided that you > > >> will do the same thing with all of its descendants". > > > Are there no defines for this? > > > > > > > Not at the moment, but I guess they can be added if really necessary. :-) > > > > But that said it doesn't have to be 1 or any specific value. Any positive number > > will have the same effect. > Thanks for point it out, Hi Lee, should I repost a patch set to define the return value > and make this one based on that? I think that would be a great way to move forward. -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog