Re: [PATCH 3/4] soundwire: bus: check if pm runtime is enabled before calling

[Ranjani Sridharan <ranjani.sridharan@linux.intel.com>]

On Thu, 2019-03-28 at 09:55 -0400, Pierre-Louis Bossart wrote:
> On 3/28/19 9:41 AM, Srinivas Kandagatla wrote:
> > Check the device has pm runtime enabled before returning error.
> > 
> > Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> > ---
> >   drivers/soundwire/bus.c | 16 ++++++++++------
> >   1 file changed, 10 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
> > index 1cbfedfc20ef..101562a6fb0d 100644
> > --- a/drivers/soundwire/bus.c
> > +++ b/drivers/soundwire/bus.c
> > @@ -327,9 +327,11 @@ int sdw_nread(struct sdw_slave *slave, u32
> > addr, size_t count, u8 *val)
> >   	if (ret < 0)
> >   		return ret;
> >   
> > -	ret = pm_runtime_get_sync(slave->bus->dev);
> > -	if (ret < 0)
> > -		return ret;
> > +	if (pm_runtime_enabled(slave->bus->dev)) {
> > +		ret = pm_runtime_get_sync(slave->bus->dev);
> 
> Is this an recommended/accepted sequence in kernel circles? I did a 
> quick git grep and don't see anyone using this sort of tests.
Hi Srinivas/Pierre,

Sorry for the delayed reply.

The only instance where I have seen the pm_runtime_get_sync() fail is
not because pm_runtime was disabled. But it is because the power is
powered off when trying to do a pm_runtime_get_sync().

I'm not very familiar with the code in soundwire yet, but is it
possible that the pm_domain supplier has powered off the soundwire
device and would cause a failure in pm_runtime_get_sync()?

Thanks,
Ranjani

> 
> 
> > +		if (ret < 0)
> > +			return ret;
> > +	}
> >   
> >   	ret = sdw_transfer(slave->bus, &msg);
> >   	pm_runtime_put(slave->bus->dev);
> 
> and the weird thing is that you don't test for the put() case?
> 
> > @@ -355,9 +357,11 @@ int sdw_nwrite(struct sdw_slave *slave, u32
> > addr, size_t count, u8 *val)
> >   	if (ret < 0)
> >   		return ret;
> >   
> > -	ret = pm_runtime_get_sync(slave->bus->dev);
> > -	if (ret < 0)
> > -		return ret;
> > +	if (pm_runtime_enabled(slave->bus->dev)) {
> > +		ret = pm_runtime_get_sync(slave->bus->dev);
> > +		if (ret < 0)
> > +			return ret;
> > +	}
> >   
> >   	ret = sdw_transfer(slave->bus, &msg);
> >   	pm_runtime_put(slave->bus->dev);
> > 
> 
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