From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lee Jones Subject: Re: [PATCH][v3] mfd: intel-lpss: Avoid resuming runtime-suspended lpss unnecessarily Date: Fri, 30 Sep 2016 01:29:43 +0100 Message-ID: <20160930002943.GC13971@dell> References: <1475125286-12167-1-git-send-email-yu.c.chen@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Received: from mail-pf0-f169.google.com ([209.85.192.169]:33391 "EHLO mail-pf0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935085AbcI3A1c (ORCPT ); Thu, 29 Sep 2016 20:27:32 -0400 Received: by mail-pf0-f169.google.com with SMTP id 21so34038979pfy.0 for ; Thu, 29 Sep 2016 17:27:31 -0700 (PDT) Content-Disposition: inline In-Reply-To: Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" Cc: Chen Yu , Linux PM , Pavel Machek , Len Brown , Linux Kernel Mailing List , Andy Shevchenko , Mika Westerberg , "Rafael J . Wysocki" On Fri, 30 Sep 2016, Rafael J. Wysocki wrote: > Hi Lee, > > On Thu, Sep 29, 2016 at 7:01 AM, 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. > > > > Suggested-by: Rafael J. Wysocki > > Acked-by: Mika Westerberg > > Reviewed-by: Andy Shevchenko > > Cc: Andy Shevchenko > > Cc: Mika Westerberg > > Cc: Rafael J. Wysocki > > Cc: Lee Jones > > Signed-off-by: Chen Yu > > If this is fine with you and you'd like to apply it, please feel free > to add my ACK to it. > > Alternatively, if you'd prefer me to apply it, please let me know. You want this in for v3.9? I just started applying patches for v3.10. If you're certain there are 0% chance of regressions, I will still apply this for v3.9 with your Ack. > > --- > > drivers/mfd/intel-lpss.c | 9 +++++++++ > > include/linux/pm.h | 7 +++++++ > > 2 files changed, 16 insertions(+) > > > > diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c > > index 41b1138..2583db8 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 DPM_DIRECT_COMPLETE; > > + /* > > * Resume both child devices before entering system sleep. This > > * ensures that they are in proper state before they get suspended. > > */ > > diff --git a/include/linux/pm.h b/include/linux/pm.h > > index 06eb353..4a788b4 100644 > > --- a/include/linux/pm.h > > +++ b/include/linux/pm.h > > @@ -786,4 +786,11 @@ enum dpm_order { > > DPM_ORDER_DEV_LAST, > > }; > > > > +/* > > + * Return this from system suspend/hibernation ->prepare() callback to > > + * request the core to leave the device runtime-suspended during system > > + * suspend if possible. > > + */ > > +#define DPM_DIRECT_COMPLETE 1 > > + > > #endif /* _LINUX_PM_H */ > > -- > > Thanks, > Rafael -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog