linux-kernel - Re: [PATCH 08/18] ASoC: cs35l56: Fix default SDW TX mixer registers

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Message-ID: <4f54a12c-c8a3-414c-b4df-3f7b25e6d524@linux.intel.com>
Date: Mon, 29 Jan 2024 18:15:14 +0100
From: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To: Richard Fitzgerald <rf@...nsource.cirrus.com>, broonie@...nel.org,
 tiwai@...e.com
Cc: alsa-devel@...a-project.org, linux-sound@...r.kernel.org,
 linux-kernel@...r.kernel.org, patches@...nsource.cirrus.com
Subject: Re: [PATCH 08/18] ASoC: cs35l56: Fix default SDW TX mixer registers



On 1/29/24 17:27, Richard Fitzgerald wrote:
> Patch the SDW TX mixer registers to silicon defaults.
> 
> CS35L56 is designed for SDCA and a generic SDCA driver would
> know nothing about these chip-specific registers. So the
> firmware sets up the SDW TX mixer registers to whatever audio
> is relevant on a specific system.
> 
> This means that the driver cannot assume the initial values
> of these registers. But Linux has ALSA controls to configure
> routing, so the registers can be patched to silicon default and
> the ALSA controls used to select what audio to feed back to the
> host capture path.

humm, which has the precedence then?
a) the values set by firmware
b) the default values set by the driver?

Also if the firmware touches those registers shouldn't they be marked as
'volatile'?


> Backport note:
> This won't apply to kernels older than v6.6.
> 
> Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
> Fixes: e49611252900 ("ASoC: cs35l56: Add driver for Cirrus Logic CS35L56")
> ---
>  sound/soc/codecs/cs35l56-shared.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/sound/soc/codecs/cs35l56-shared.c b/sound/soc/codecs/cs35l56-shared.c
> index 35789ffc63af..a812abf90836 100644
> --- a/sound/soc/codecs/cs35l56-shared.c
> +++ b/sound/soc/codecs/cs35l56-shared.c
> @@ -12,6 +12,15 @@
>  #include "cs35l56.h"
>  
>  static const struct reg_sequence cs35l56_patch[] = {
> +	/*
> +	 * Firmware can change these to non-defaults to satisfy SDCA.
> +	 * Ensure that they are at known defaults.
> +	 */
> +	{ CS35L56_SWIRE_DP3_CH1_INPUT,		0x00000018 },
> +	{ CS35L56_SWIRE_DP3_CH2_INPUT,		0x00000019 },
> +	{ CS35L56_SWIRE_DP3_CH3_INPUT,		0x00000029 },
> +	{ CS35L56_SWIRE_DP3_CH4_INPUT,		0x00000028 },
> +
>  	/* These are not reset by a soft-reset, so patch to defaults. */
>  	{ CS35L56_MAIN_RENDER_USER_MUTE,	0x00000000 },
>  	{ CS35L56_MAIN_RENDER_USER_VOLUME,	0x00000000 },