Re: [PATCH 1/3] ASoC: tas2783: let regmap-sdw-mbq poll for deferred transactions

[Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>]

> Thanks for taking the time to review this. I am a bit of a kernel noob, 
> but I completely agree with you and the spec: FUNCTION_STATUS cannot be 
> deferred.
> 
> I think my commit message caused a misunderstanding. The patch doesn't 
> defer the status read:
> 
> The hardware is actually returning COMMAND_IGNORED for the UDMPU23 
> Cluster Index write, which is the only control tas2783_sdca_deferrable() 
> flags as true.
> 
> I only added FUNCTION_STATUS to mbq_size to expose it to -> 
> readable_reg(). Without that, regmap_sdw_mbq_poll_busy() considers the 
> status register unreadable, skips checking the busy bit for the deferred 
> UDMPU23 write, and instantly fails.

I think your patch exposes a problem in the initial implementation of
regmap_sdw_mbq_poll_busy(). FUNCTION_STATUS is a readable register by
default, not sure why we would ever need to test if it's readable.

Adding Charles for additional comments, this part looks questionable
with a possible register side-effect.

reg = SDW_SDCA_CTL(SDW_SDCA_CTL_FUNC(reg), 0,
		   SDCA_CTL_ENTITY_0_FUNCTION_STATUS, 0);

if (ctx->readable_reg(dev, reg)) { <<< are we testing the correct reg?