Re: [PATCH v3 2/2] ASoC: Intel: Add period size constraint on strago board

[Pierre-Louis Bossart]

On 8/3/20 11:33 PM, Lu, Brent wrote:
> > For avoid further misunderstanding: it's fine that CRAS *uses* such a short
> > period.  It's often required for achieving a short latency.
> >
> > However, the question is whether the driver can set *only* this value for
> > making it working.  IOW, if we don't have this constraint, what actually
> > happens?  If the driver gives the period size alignment, wouldn't CRAS
> > choose 240?
>
> It won't. Without the constraint it becomes 432. Actually CRAS does not set
> period size specifically so the value depends on the constraint rules.

I don't get this. If the platform driver already stated 240 and 960 
samples why would 432 be chosen? Doesn't this mean the constraint is not 
applied?

> [   52.011146] sound pcmC1D0p: hw_param
> [   52.011152] sound pcmC1D0p:   ACCESS 0x1
> [   52.011155] sound pcmC1D0p:   FORMAT 0x4
> [   52.011158] sound pcmC1D0p:   SUBFORMAT 0x1
> [   52.011161] sound pcmC1D0p:   SAMPLE_BITS [16:16]
> [   52.011164] sound pcmC1D0p:   FRAME_BITS [32:32]
> [   52.011167] sound pcmC1D0p:   CHANNELS [2:2]
> [   52.011170] sound pcmC1D0p:   RATE [48000:48000]
> [   52.011173] sound pcmC1D0p:   PERIOD_TIME [9000:9000]
> [   52.011176] sound pcmC1D0p:   PERIOD_SIZE [432:432]
> [   52.011179] sound pcmC1D0p:   PERIOD_BYTES [1728:1728]
> [   52.011182] sound pcmC1D0p:   PERIODS [474:474]
> [   52.011185] sound pcmC1D0p:   BUFFER_TIME [4266000:4266000]
> [   52.011188] sound pcmC1D0p:   BUFFER_SIZE [204768:204768]
> [   52.011191] sound pcmC1D0p:   BUFFER_BYTES [819072:819072]
> [   52.011194] sound pcmC1D0p:   TICK_TIME [0:0]
>
> Regards,
> Brent
>
> > Takashi