Messages in this thread | | | Date | Tue, 13 Sep 2016 09:24:22 +0100 | From | Lee Jones <> | Subject | Re: [PATCH][RFC] mfd: intel-lpss: Avoid resuming runtime-suspended lpss unnecessarily |
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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 <andriy.shevchenko@linux.intel.com> > > > Cc: Mika Westerberg <mika.westerberg@linux.intel.com> > > > Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > Signed-off-by: Chen Yu <yu.c.chen@intel.com> > > > --- > > > 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?
-- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog
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