Re: [PATCH] ASoC: tas2783-sdw: power the Function up before preparing the port

[Andrey Golovko]

On Wed, Aug 13, 2026 at 09:18:58PM +0000, Robin Everaars wrote:

> thanks. One clarification about my negative v1 result: it was not an
> active-playback resume test. The controlled pre-suspend tone had completed
> before system suspend.

Thank you for going back and checking, that is a useful correction.  I
had been reading your result as evidence about the resume ioctl, and it
is not.

Your second case is the one I would expect to have worked on v1: a fresh
pw-play after the sink was suspended opens the PCM again, so it goes
through hw_params() and prepare(), and that is the path v1 already
covered.  It failing on v7.1.7 fits your own attribution to the missing
b627da430357 - without it the DAPM writes that follow are dropped
against a stale cache, so the Function never comes up no matter how well
the port is prepared.  So yes, for-next rather than another v7.1.7 cycle.

For the third case I would expect it to still fail, and that is the
point of running it: the PCM core does not trigger a stream that was
left PREPARED, so nothing in the codec or machine driver gets a chance
to act.  sdw_prepare_stream() on a stream still marked PREPARED is a
no-op too, so even a call from there would not help.  It needs the
stream state invalidated when the peripheral goes UNATTACHED and comes
back.  If your readout shows PrepareCtrl=0x0 while the stream is
running, that is the same gap and not a second bug.

The module is on its way off-list.  It reads and prints DP1
PrepareCtrl, PrepareStatus, the ChannelEn of the current bank and the
PDE23 requested and actual power states, straight over the bus with
sdw_read_no_pm(), so the codec regmap cache is out of the picture.  It
only reads unless you ask it to write.

For a shape to compare against, here is what the resume-ioctl case gave
on this machine, unpatched kernel to the left, v2 to the right:

  DP1 PrepareCtrl before/after   0x1,0x2 -> 0x0,0x0   0x1,0x2 -> 0x1,0x2
  PDE23 req/act after            0x3/0x3              0x0/0x0
  440/660 Hz tone after          -1.7/+1.8 dB         +73.7/+88.5 dB

The tone figures are levels in narrow bands around 440 and 660 Hz in a
three-second capture from the built-in microphone, on a scale where a
capture of silence reads about 0 dB in the same bands.  The absolute
numbers say nothing outside this machine; noise floor against signal
does.

v2 of the series is at

  https://lore.kernel.org/linux-sound/20260813194000.10412-1-andrey.golovko@xxxxxxxxx/

Andrey