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

[Nicolin Chen]

On Mon, Apr 03, 2017 at 01:32:42PM -0700, Caleb Crome 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
> * 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.

What's your test case for the alignment? IIRC, you only needed
the FIFO to be pre-filled with data input so that SSI will not
encounter any FIFO underrun after enabling TE bit. That's why
there is a for-loop before this regmap_update_bits().

> 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);

However, this patch seems to merely set the RE bit. It shouldn't
affect that test case since the SSIEN bit is still set prior to
the TE bit.