On Tue, May 28, 2013 at 02:53:47PM +0200, Rafael J. Wysocki wrote:
> On Monday, May 13, 2013 01:50:18 PM Rafael J. Wysocki wrote:
> > On Monday, May 13, 2013 02:05:27 PM Mika Westerberg wrote:
> > > If the device is using autosuspend we should honor that and call
> > > pm_runtime_autosuspend() instead of pm_runtime_suspend(). Failing to do so
> > > causes the device to be suspended immediately even though it expects to be
> > > suspended only when the autosuspend delay is expired.
> > >
> > > Signed-off-by: Mika Westerberg <mika.westerb...@linux.intel.com>
> > > ---
> > > drivers/base/power/generic_ops.c | 5 ++++-
> > > 1 file changed, 4 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/base/power/generic_ops.c
> > > b/drivers/base/power/generic_ops.c
> > > index bfd898b..19786ca 100644
> > > --- a/drivers/base/power/generic_ops.c
> > > +++ b/drivers/base/power/generic_ops.c
> > > @@ -29,7 +29,10 @@ int pm_generic_runtime_idle(struct device *dev)
> > > return ret;
> > > }
> > >
> > > - pm_runtime_suspend(dev);
> > > + if (dev->power.use_autosuspend)
> > > + pm_runtime_autosuspend(dev);
> > > + else
> > > + pm_runtime_suspend(dev);
> > > return 0;
> >
> > First of all, this is racy (power.use_autosuspend shoud be accessed under
> > power.lock).
> >
> > Second, this is not the only place we'd need to make this change (the
> > analogous
> > function for PCI is one example, but there may be others).
> >
> > Finally, I'm not sure how to address this problem in general. It may be
> > better
> > to simply modify rpm_idle() and remove pm_generic_runtime_idle() etc.
> > entirely.
> >
> > I'll have a look at that, thanks for pointing out the problem.
>
> I'm not sure if the core is the right place to address this, because it's
> not entirely clear if all drivers using autosuspend will have the same policy
> with respect to pm_runtime_idle() (i.e. to avoid suspending immediately if
> the suspend delay timer is active).
>
> In my opinion it'd be better to address that in the driver by adding a
> .runtime_idle() callback executing pm_runtime_autosuspend(dev) and returning
> -EBUSY.
Makes sense. I did a quick test with following patch and it seems to fix
the issue for i2c-designware driver.
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c
b/drivers/i2c/busses/i2c-designware-platdrv.c
index 966a554..af8be8f 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -267,7 +267,22 @@ static int dw_i2c_resume(struct device *dev)
}
#endif
-static SIMPLE_DEV_PM_OPS(dw_i2c_dev_pm_ops, dw_i2c_suspend, dw_i2c_resume);
+#ifdef CONFIG_PM_RUNTIME
+static int dw_i2c_runtime_idle(struct device *dev)
+{
+ /*
+ * Always schedule autosuspend regardless of what runtime PM the
+ * client devices use.
+ */
+ pm_runtime_autosuspend(dev);
+ return -EBUSY;
+}
+#endif
+
+static const struct dev_pm_ops dw_i2c_dev_pm_ops = {
+ SET_SYSTEM_SLEEP_PM_OPS(dw_i2c_suspend, dw_i2c_resume)
+ SET_RUNTIME_PM_OPS(NULL, NULL, dw_i2c_runtime_idle)
+};
/* work with hotplug and coldplug */
MODULE_ALIAS("platform:i2c_designware");
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