[PATCH] soundwire: fix pm_runtime_get_sync return code checks

[PATCH] soundwire: fix pm_runtime_get_sync return code checks

[Jan Kotas]

When PM is disabled it returns -EACCES, which is currently
threated as an error, and prevents accessing the slave's
registers.

This patch ignores the -EACCES return value from
pm_runtime_get_sync() to let the SoundWire work in systems
without runtime PM.

Signed-off-by: Jan Kotas <jank@cadence.com>
---
 drivers/soundwire/bus.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index 1cbfedfc2..6567ff439 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -328,7 +328,7 @@ int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
 		return ret;
 
 	ret = pm_runtime_get_sync(slave->bus->dev);
-	if (ret < 0)
+	if (ret < 0 && ret != -EACCES)
 		return ret;
 
 	ret = sdw_transfer(slave->bus, &msg);
@@ -356,7 +356,7 @@ int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
 		return ret;
 
 	ret = pm_runtime_get_sync(slave->bus->dev);
-	if (ret < 0)
+	if (ret < 0 && ret != -EACCES)
 		return ret;
 
 	ret = sdw_transfer(slave->bus, &msg);
-- 
2.15.0

Re: [PATCH] soundwire: fix pm_runtime_get_sync return code checks

[Jan Kotas]

> On 5 Apr 2019, at 17:04, Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> wrote:
> 
> On 4/5/19 2:26 AM, Jan Kotas wrote:
>> 
>>  
>>  	ret = pm_runtime_get_sync(slave->bus->dev);
>> -	if (ret < 0)
>> +	if (ret < 0 && ret != -EACCES)
>> 
> There was a patch submitted on 3/28 by Srinivas Kandagatla who suggested an alternate solution for exactly the same code.
> 
> +	if (pm_runtime_enabled(slave->bus->dev)) {
> +		ret = pm_runtime_get_sync(slave->bus->dev);
> +		if (ret < 0)
> +			return ret;
> 
> I am far from an expert on pm_runtime but Srinivas' solution looks more elegant to me.

Hello Pierre,

Please take a look at this patch, that was my inspiration:
https://lists.linuxfoundation.org/pipermail/linux-pm/2011-June/031930.html

I also took a look, and it seems the value returned by 
pm_runtime_get_syncis simply ignored in a lot of places, 
so checking its value may be excessive.

Regards,
Jan

Re: [alsa-devel] [PATCH] soundwire: fix pm_runtime_get_sync return code checks

[Pierre-Louis Bossart]

On 4/8/19 2:12 AM, Jan Kotas wrote:
> 
> 
>> On 5 Apr 2019, at 17:04, Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> wrote:
>>
>> On 4/5/19 2:26 AM, Jan Kotas wrote:
>>>
>>>   
>>>   	ret = pm_runtime_get_sync(slave->bus->dev);
>>> -	if (ret < 0)
>>> +	if (ret < 0 && ret != -EACCES)
>>>
>> There was a patch submitted on 3/28 by Srinivas Kandagatla who suggested an alternate solution for exactly the same code.
>>
>> +	if (pm_runtime_enabled(slave->bus->dev)) {
>> +		ret = pm_runtime_get_sync(slave->bus->dev);
>> +		if (ret < 0)
>> +			return ret;
>>
>> I am far from an expert on pm_runtime but Srinivas' solution looks more elegant to me.
> 
> Hello Pierre,
> 
> Please take a look at this patch, that was my inspiration:
> https://lists.linuxfoundation.org/pipermail/linux-pm/2011-June/031930.html

The two patches seems to be identical:

static inline bool pm_runtime_enabled(struct device *dev)
{
	return !dev->power.disable_depth;
}

static int rpm_resume()
[...]
else if (dev->power.disable_depth > 0)
		retval = -EACCES;


However I am still not clear on why this might fail.

I can only think of one possible explanation: there is no explicit 
pm_runtime_enable() in the soundwire code, so maybe the expectation is 
that the pm_runtime status is inherited from the parent (in the intel 
case the PCI driver), and that's missing in non-intel configurations?

> I also took a look, and it seems the value returned by
> pm_runtime_get_syncis simply ignored in a lot of places,
> so checking its value may be excessive.
But not checking seems careless at best...

Re: [alsa-devel] [PATCH] soundwire: fix pm_runtime_get_sync return code checks

[Vinod Koul]

On 08-04-19, 12:43, Pierre-Louis Bossart wrote:
> 
> 
> On 4/8/19 2:12 AM, Jan Kotas wrote:
> > 
> > 
> > > On 5 Apr 2019, at 17:04, Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> wrote:
> > > 
> > > On 4/5/19 2:26 AM, Jan Kotas wrote:
> > > > 
> > > >   	ret = pm_runtime_get_sync(slave->bus->dev);
> > > > -	if (ret < 0)
> > > > +	if (ret < 0 && ret != -EACCES)
> > > > 
> > > There was a patch submitted on 3/28 by Srinivas Kandagatla who suggested an alternate solution for exactly the same code.
> > > 
> > > +	if (pm_runtime_enabled(slave->bus->dev)) {
> > > +		ret = pm_runtime_get_sync(slave->bus->dev);
> > > +		if (ret < 0)
> > > +			return ret;
> > > 
> > > I am far from an expert on pm_runtime but Srinivas' solution looks more elegant to me.
> > 
> > Hello Pierre,
> > 
> > Please take a look at this patch, that was my inspiration:
> > https://lists.linuxfoundation.org/pipermail/linux-pm/2011-June/031930.html
> 
> The two patches seems to be identical:
> 
> static inline bool pm_runtime_enabled(struct device *dev)
> {
> 	return !dev->power.disable_depth;
> }
> 
> static int rpm_resume()
> [...]
> else if (dev->power.disable_depth > 0)
> 		retval = -EACCES;
> 
> 
> However I am still not clear on why this might fail.
> 
> I can only think of one possible explanation: there is no explicit
> pm_runtime_enable() in the soundwire code, so maybe the expectation is that
> the pm_runtime status is inherited from the parent (in the intel case the
> PCI driver), and that's missing in non-intel configurations?

IIRC that needs to be called by the Intel driver and those patches were
not upstreamed. So we dont have fully supported PM on upstream yet!

> 
> > I also took a look, and it seems the value returned by
> > pm_runtime_get_syncis simply ignored in a lot of places,
> > so checking its value may be excessive.
> But not checking seems careless at best...

-- 
~Vinod