On Fri, Sep 13, 2013 at 07:30:55AM -0700, Kevin Hilman wrote:
> Mika Westerberg <mika.westerb...@linux.intel.com> writes:
>
> > On Thu, Sep 12, 2013 at 02:34:21PM -0700, Kevin Hilman wrote:
> >> > diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> >> > index f32ca29..44374b4 100644
> >> > --- a/drivers/i2c/i2c-core.c
> >> > +++ b/drivers/i2c/i2c-core.c
> >> > @@ -248,11 +248,30 @@ static int i2c_device_probe(struct device *dev)
> >> > client->flags &
> >> > I2C_CLIENT_WAKE);
> >> > dev_dbg(dev, "probe\n");
> >> >
> >> > + /* Make sure the adapter is active */
> >> > + pm_runtime_get_sync(&client->adapter->dev);
> >> > +
> >> > + /*
> >> > + * Enable runtime PM for the client device. If the client wants
> >> > to
> >> > + * participate on runtime PM it should call pm_runtime_put() in
> >> > its
> >> > + * probe() callback.
> >> > + */
> >> > + pm_runtime_get_noresume(&client->dev);
> >> > + pm_runtime_set_active(&client->dev);
> >>
> >> Why the set_active here?
> >>
> >> For hardware that is disabled/powered-off on startup, there will now be
> >> a mismatch between the hardware state an the RPM core state.
> >
> > The call to pm_runtime_get_noresume() should make sure that the device is
> > in active state (at least in state where it can access the bus) if I'm
> > understanding this right.
>
> No, after _get_noresume(), nothing happens to the hardware. It simply
> increments the usecount. From pm_runtime.h:
>
> static inline void pm_runtime_get_noresume(struct device *dev)
> {
> atomic_inc(&dev->power.usage_count);
> }
>
> So after the _get_noresume() and _set_active() you're very likely to
> have a disconnect between the hardware state and what state RPM thinks
> the hardware is in.
Good point.
I suppose calling pm_runtime_get() here would work (and make the state
active in all case)? I used _noresume() here because at this point the
driver itself hasn't had change to install it's RPM hooks.
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