Speaker pops with max98357a on rk3399-gru-kevin since v5.7

[Alper Nebi Yasak]

On 17/07/2020 05:27, Tzung-Bi Shih wrote:
> I am not convinced the pop comes from 128f825aeab7.

Maybe some pre-existing defect in rk3399_gru_sound got exposed by
128f825aeab7 or the machine driver needs some changes to complement
that commit?

> (I don't have a rk3399-gru-kevin so I got another test machine with MAX98357A.)
> (I was testing with and without an audio server.)

Your observations are also a bit different from mine, which IMO also
suggests the machine driver is the true culprit -- I'd guess the pops
you hear would be from a different problem in your test machine's
machine driver?

(Let me restate my observations to contrast with yours, as I feel my
previous explanation was too wordy:)

> Observations:
> - I can hear the pop either with or without 128f825aeab7 (with and
> without sdmode-delay).

I never hear pops without 128f825aeab7, but always hear pops with it.
(no change when I remove "sdmode-delay" from the device-tree)

> - The pop noise is not always.  Higher probability after stopping
> playback than before starting.

I always hear one pop when starting playback, and two pops (with a few
seconds between them) when stopping playback.