Re: [PATCH 2/2] ASoC: cs42l43: Fix headphone output by properly disabling HP clamp

[Charles Keepax <ckeepax@opensource.cirrus.com>]

On Sun, Jan 11, 2026 at 08:13:43PM -0700, Cole Leavitt wrote:
> The CS42L43 codec requires proper configuration of the headphone amplifier
> clamp circuitry for audio output to work. Two issues were preventing
> headphone audio:
> 
> 1. The STEREO_MIC_CLAMP_CTRL register (0x100c4) requires both bit 0
>    (SMIC_HPAMP_CLAMP_DIS_FRC) AND bit 1 (SMIC_HPAMP_CLAMP_DIS_FRC_VAL)
>    to be set to properly disable the HP amp clamp. The driver was only
>    setting bit 0, which enables force mode but leaves the clamp enabled.

This bit isn't a general clamp it moves the clamp under control
of the stereo mic logic. The normal playback paths should
override these settings when brought up.

> 2. When switching to headphone or line-out mode via the Jack Override
>    control, the HS_CLAMP_DISABLE bit (bit 28) in the HS2 register must
>    be set to disable the headset clamp circuitry.

This clamps pins 3/4 to ground (gnd/mic), not the signal pins, as
such the clamp should be active for both headphone and line-out
cases.

> Without these fixes, the headphone amplifier output is clamped to ground
> and no audio is heard despite correct DAPM routing.

Are you really having no sound without this patch and sound with
this patch? Could you confirm that is the case, making sure
reverting this one change is the difference between your two
tests. Could you also describe a little more about how you get
into the failing state? Is it a simple case of plug in headphones
no sound? cs42l43 is a pretty well tested device it seems unlikely
something is fundamentally wrong with the clamping.

Thanks,
Charles