Re: [PATCH 3/3] arm64: dts: rockchip: Assign ES8316 MCLK rate on rk3588-rock-5b

[Cristian Ciocaltea <cristian.ciocaltea@collabora.com>]

On 5/24/23 13:39, Mark Brown wrote:
> On Wed, May 24, 2023 at 10:41:56AM +0300, Cristian Ciocaltea wrote:
>> The I2S0_8CH_MCLKOUT clock rate on Rock 5B board defaults to 12 MHz and
>> it is used to provide the master clock (MCLK) for the ES8316 audio
>> codec.
>>
>> On sound card initialization, this limits the allowed sample rates
>> according to the MCLK/LRCK ratios supported by the codec, which results
>> in the following non-standard rates: 15625, 30000, 31250, 46875.
>>
>> Hence, the very first access of the sound card fails:
>>
>>   Broken configuration for playback: no configurations available: Invalid argument
>>   Setting of hwparams failed: Invalid argument
>>
>> However, all subsequent attempts will succeed, as the audio graph card
>> will request a correct clock frequency, based on the stream sample rate
>> and the multiplication factor.
>>
>> Assign MCLK to 12.288 MHz, which allows the codec to advertise most of
>> the standard sample rates.
> 
> Surely this is irrelevant with your previous change, and if the clock is
> freely reprogrammable as it sounds even harmful given that it'll
> restrict rates that are not available with the selected MCLK?

As mentioned in the previous patch description, there's a bad timing
with es8316_pcm_startup() being executed before the 2nd call to
es8316_set_dai_sysclk(), with the effect that the new/updated
rate constraints won't be used until the next playback attempt.

Hence the approach here was to ensure the initial list of restricted
rates is sane, by (pre)assigning a proper MCLK. Alternatively, we could
have used an unsupported MCLK and, with the help of the previous patch,
we would have ended up with no restrictions applied on es8316_pcm_startup().