Re: [PATCH V2] ASoC: Intel: boards: Use FS as nau8825 sysclk in nau88125_* machine

Cezary Rojewski
2020-05-05T15:57:45Z

>>>
>>> 2) Currently Skylake does not output MCLK/FS when the back-end DAI op
>>> hw_param is called, so we cannot switch to MCLK/FS in hw_param. This
>>> patch reduces pop by letting nau8825 keep using its internal VCO clock
>>> during widget power up sequence, until SNDRV_PCM_TRIGGER_START when
>>> MCLK/FS is available. Once device resumes, the system will only enable
>>> power sequence for playback without doing hardware parameter, audio
>>> format, and PLL configure. In the mean time, the jack detecion sequence
>>> has changed PLL parameters and switched to internal clock. Thus, the
>>> playback signal distorted without correct PLL parameters. That is why
>>> we need to configure the PLL again in SNDRV_PCM_TRIGGER_RESUME case.
>>
>> IIRC the FS can be controlled with the clk_ api with the Skylake driver,
>> as done for some KBL platforms. Or is this not supported by the firmware
>> used by this machine?
>
> According to Ben, SKL had limitations in FW for managing the clk's
> back in the days.
> Can you point to the other driver you mention so we can cross check?
>

Skylake driver is found within:
/sound/soc/intel/skylake
directory.

"SKL had limitations in FW" - that's misleading. This is neither FW
issue nor HW 'limitation'. SKL is an older platform and its goals and
design was different than say APL+. Basically, your needs do not align
with what's present on SKL hw.

Czarek