[PATCH][v2] mfd: intel-lpss: Avoid resuming runtime-suspended lpss unnecessarily

[PATCH][v2] mfd: intel-lpss: Avoid resuming runtime-suspended lpss unnecessarily

[Chen Yu]

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.*/
+#define DPM_DIRECT_COMPLETE 1
+
 #endif /* _LINUX_PM_H */
-- 
2.7.4

Re: [PATCH][v2] mfd: intel-lpss: Avoid resuming runtime-suspended lpss unnecessarily

[Rafael J. Wysocki]

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.
 */

> +#define DPM_DIRECT_COMPLETE 1
> +
>  #endif /* _LINUX_PM_H */
> --

But it is fine by me overall.

Thanks,
Rafael

Re: [PATCH][v2] mfd: intel-lpss: Avoid resuming runtime-suspended lpss unnecessarily

[Chen Yu]

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