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: [email protected]; 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 <[email protected]> > > >>>> Cc: Mika Westerberg <[email protected]> > > >>>> Cc: Rafael J. Wysocki <[email protected]> > > >>>> Signed-off-by: Chen Yu <[email protected]> > > >>>> --- > > >>>> 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
