[alsa-devel] [PATCH v2] ASoC: fsl_ssi: Fix channel swap on playback start

[Fabio Estevam]

Hi Caleb,

On Mon, Apr 3, 2017 at 5:32 PM, Caleb Crome <caleb at crome.org> wrote:

> This patch definitely breaks the i.mx6 channel alignment.  In fact it
> breaks it so that the channels are never aligned properly.
>
> My test setup is as follows:
> * Get vanilla kernel, tag v4.11-rc5

Thanks for testing.

Just tested 4.11-rc5. It needs this additional patch:
https://patchwork.ozlabs.org/patch/745349/

otherwise pinctrl hog is broken and then sgtl5000 does not probe due
to the lack of MCLK.

I am using the original imx6dl-wandboard.dtb on my tests with no
hardware changes.

The test I am running is simple: just run the following script on the wandboard:

#!/bin/bash

while true
do
aplay swap_test.wav& sleep 1; killall aplay
done

You can get swap_test.wav file that consists of silence in the left
channel and none silence in the right channel from here:
https://www.dropbox.com/s/4zt0jvmtx34ic9x/swap_test.wav?dl=0

Then keep listening the left channel. In about one out of ten times
you will get non-silence there, indicating a swap.

> * apply a couple patches to allow AUD4 on the wandboard external
> connectors (and disable internal audio)
> * Test results:  v4.11-rc5 works flawlessly using Arnaud's atest
> program.  No channel slips, no issues at all.
> * Apply this patch, recompile, build.
> * Channel alignment fails.  The channels never get aligned properly.
>
> Am I right that the *only* change is this one-liner, and ignore the
> previous non V2 version of this patch?
>> -               regmap_update_bits(regs, CCSR_SSI_SCR, vals->scr, vals->scr);
>> +               regmap_update_bits(regs, CCSR_SSI_SCR,
>> +                       CCSR_SSI_SCR_SSIEN | CCSR_SSI_SCR_TE | CCSR_SSI_SCR_RE,
>> +                       CCSR_SSI_SCR_SSIEN | CCSR_SSI_SCR_TE | CCSR_SSI_SCR_RE);

Yes, with only this change I do not get the swap anymore.

If you have a chance to run this method, please let me know how it goes.

Thanks