Re: [PATCH QUESTION] ASoC: qcom: sdm845: use DSP_A format for TDM codec DAIs

[David Heidelberg]

On 14/06/2026 23:40, Srinivas Kandagatla wrote:
> On 6/14/26 8:26 AM, David Heidelberg wrote:
> > On 14/06/2026 01:53, Mark Brown wrote:
> > > On Sat, Jun 13, 2026 at 09:55:59PM +0200, David Heidelberg via B4
> > > Relay wrote:
> > >
> > > > Currently this worked only because the cs35l36
> > > > codec mapped both DSP_A and DSP_B to the same hardware register value
> > > > (asp_fmt = 0), which is inherently DSP_A timing.
> > >
> > > > The CPU-side AFE is configured with qcom,tdm-data-delay = <1> which
> > > > produces DSP_A framing.
> > > > The codec format should match what is actually on the wire.
> > >
> > > > So I'm pretty lost if I should go fixing cs35l36 or sdm845.c.
> > >
> > > That sounds like both.  The Cirrus driver is definitely buggy if it's
> > > mapping DSP A and B to the same register value, at least one of those is
> > > wrong.
> >
> > I need to clarify. The CS35L36 supports by default only DSP_A, but when
> > extended to "take DSP_B", speaker just works.
> >
> > This was done previously.
> >
> > Since there isn't any different configuration on the codec side when
> > added DSP_B into same codepath as DSP_A, I would assume QCOM ASoC send
> > DSP_A, just marking it as DSP_B ?
>
>
> 		qcom,tdm-sync-mode = <0>;
> 		qcom,tdm-sync-src = <1>;
> sets the short sync with 1 clk delay making it DSP_A.
>
> for DSP_B you would need, no delay.

Sure, does that mean the sdm845.c is currently correctly setting 
SND_SOC_DAIFMT_DSP_B there? or there is some missing part of logic deciding it?

Because the reason audio works when I convince driver either:

a) sdm845 ASoC it uses BSP_A instead of B ... or
b) cs35l36 it uses BSP_B instead of A

implies to me, that:
 1. both devices are setting the HW to either BSP_A or BSP_B mode (just don't 
know which one)
 2. but the driver flag for ASoC or codec we setting on the driver side is wrong

If one side really used BSP_A and other BSP_B, the audio should be at best 
heavily distorted, right?

Please correct me, if I misunderstood or if there is nice doc I could read about it.

Thanks
David

P.S. I did quick search what close-to-mainline repo has for Pixel 3a to reach 
working audio and it's slightly different, see [1]. There isn't any change done 
to the cs35l36 driver in the sdm670 tree.

[1] 
https://gitlab.com/sdm670-mainline/linux/-/commit/9eba5aa993f5fb7b4bf5cc936ec22852987d3f9f

> --srini
> > There isn't any other consumer to check against and I would assume
> > incorrectly configured TDM slot would lead - at least - to disorted output.
> >
> > The reference (which now works) is here [1].
> >
> > David
> >
> > [1] https://codeberg.org/sdm845/linux/commits/branch/b4/pixel3-audio