Hi, 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". Thanks, Yu
