Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> 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.
Kevin
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