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'? > + /* > * 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
