Messages in this thread | | | Date | Thu, 29 Sep 2016 12:59:59 +0800 | From | Chen Yu <> | Subject | Re: [PATCH][v2] mfd: intel-lpss: Avoid resuming runtime-suspended lpss unnecessarily |
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On Wed, Sep 28, 2016 at 11:48:40PM +0200, Rafael J. Wysocki wrote: > On Wed, Sep 28, 2016 at 6:29 PM, Chen Yu <yu.c.chen@intel.com> 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 <rafael.j.wysocki@intel.com> > > Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com> > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > > 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> > > Cc: Lee Jones <lee.jones@linaro.org> > > Signed-off-by: Chen Yu <yu.c.chen@intel.com> > > --- > > drivers/mfd/intel-lpss.c | 9 +++++++++ > > include/linux/pm.h | 3 +++ > > 2 files changed, 12 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..5606ad9 100644 > > --- a/include/linux/pm.h > > +++ b/include/linux/pm.h > > @@ -786,4 +786,7 @@ enum dpm_order { > > DPM_ORDER_DEV_LAST, > > }; > > > > +/* The device is OK to remain runtime-suspended during suspend.*/ > > /* > * Return this from system suspend/hibernation ->prepare() callback to > request the > * core to leave the device runtime-suspended during system suspend if possible. > */ > I've taken this comment in a new version, thanks! > > +#define DPM_DIRECT_COMPLETE 1 > > + > > #endif /* _LINUX_PM_H */ > > -- > > But it is fine by me overall. > > Thanks, > Rafael
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