[RFC PATCH 2/3] ASoC: Intel: bdw-rt5677: fix module load/unload issues

[Pierre-Louis Bossart]

On 3/5/20 7:36 AM, Mark Brown wrote:
> On Thu, Mar 05, 2020 at 07:06:15AM -0600, Pierre-Louis Bossart wrote:
>> The use of devm_gpiod_get() in a dailink .init() callback generates issues
>> when unloading modules. The dependencies between modules are not well
>> handled and the snd_soc_rt5677 module cannot be removed:
> 
> In what way are the dependencies not well managed and why aren't we
> requesting the GPIO on device model probe anyway?

there are a couple of machine drivers where the gpios are requested from 
the machine driver. I have no idea what it is done this way, maybe the 
codec exposes a gpiochip that's used later? I was hoping that Andy can 
help, I don't fully get the acpi mapping and all.

see the code here for reference:

https://elixir.bootlin.com/linux/v5.6-rc4/source/sound/soc/intel/boards/bdw-rt5677.c#L250

The issue happens when running our test scripts, which do a set a rmmod 
in a specific order: rmmod of the machine driver, then doing an rmmod of 
the codec driver. Somehow the second fails with the 'module in use error'.

It's probably because the devm_ release does not happen when the card is 
unregistered and the machine driver resources released since we use the 
component device. There might very well be a bug somewhere in the devm_ 
handling, I just don't have a clue how to debug this - and the .exit() 
makes sense regardless in other cases unrelated to GPIOs.