Re: [PATCH 1/2] ASoC: qcom: audioreach: use a 32-bit container for S24_LE PCM

[Srinivas Kandagatla <srinivas.kandagatla@oss.qualcomm.com>]

On 11/11/26 10:54 AM, Marc Herrero via B4 Relay wrote:
> From: Marc Herrero <marcht@proton.me>
> 
> SNDRV_PCM_FORMAT_S24_LE carries 24 valid bits in a 32-bit container, but
> audioreach_shmem_set_media_format() and audioreach_pcm_set_media_format()
> set bits_per_sample = bit_width = 24 in PARAM_ID_MEDIA_FORMAT and
> PARAM_ID_PCM_OUTPUT_FORMAT_CFG, which tells the DSP that the samples are
> packed 3-byte words.
> 
> q6apm-dai advertises S24_LE, so with a topology that allows it on a
> playback front end the DSP walks the buffer with the wrong stride. On
> QCS6490 (Radxa Dragon Q6A) this crashes the ADSP audio_process:
> 
>   PDM: service 'audio_process' crash: 'EX:audio_process:0x2:...'
>   q6apm-lpass-dais ...: Failed to start APM port 113
>   remoteproc remoteproc0: crash detected in adsp: type fatal error
> 
> Use the container size (32) for 24-bit data and keep bit_width = 24,
> alignment = PCM_LSB_ALIGNED and q_factor = 23. With this change S24_LE
> playback works on the headphone path (codec DMA RX -> LPASS RX macro ->
> WCD9385), tested with the back end at S16_LE, S24_LE and S32_LE and at
> 48, 96 and 192 kHz.
> 
> The DSP then reads each 32-bit word as Q23, so S24_LE samples must be
> sign-extended into the top byte, as alsa-lib's conversions do.
> 
> Fixes: 25ab80db6b13 ("ASoC: qdsp6: audioreach: add module configuration command helpers")
> Cc: stable@vger.kernel.org
> Signed-off-by: Marc Herrero <marcht@proton.me>
> ---

Thanks Marc for fixing this,

>  sound/soc/qcom/qdsp6/audioreach.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/soc/qcom/qdsp6/audioreach.c b/sound/soc/qcom/qdsp6/audioreach.c
> index d2dc5d37bccf..937506edf34a 100644
> --- a/sound/soc/qcom/qdsp6/audioreach.c
> +++ b/sound/soc/qcom/qdsp6/audioreach.c
> @@ -1216,7 +1216,7 @@ static int audioreach_pcm_set_media_format(struct q6apm_graph *graph,
>  	media_cfg->interleaved = module->interleave_type;
>  	media_cfg->num_channels = mcfg->num_channels;
>  	media_cfg->q_factor = mcfg->bit_width - 1;
> -	media_cfg->bits_per_sample = mcfg->bit_width;
> +	media_cfg->bits_per_sample = mcfg->bit_width == 24 ? 32 : mcfg->bit_width;

I think it will be worth adding a comment about the wire format vs the
sample format so it helps others.

other than that it looks good to me.

Reviewed-by: Srinivas Kandagatla<srinivas.kandagatla@oss.qualcomm.com>

--Srini


>  	/* Convert the physical mapping to a logical mapping of the channels */
>  	for (i = 0, j = 0; i < AR_PCM_MAX_NUM_CHANNEL && j < mcfg->num_channels; i++) {
>  		if (!mcfg->channel_map[i])
> @@ -1308,7 +1308,7 @@ static int audioreach_shmem_set_media_format(struct q6apm_graph *graph,
>  		cfg->sample_rate = mcfg->sample_rate;
>  		cfg->bit_width = mcfg->bit_width;
>  		cfg->alignment = PCM_LSB_ALIGNED;
> -		cfg->bits_per_sample = mcfg->bit_width;
> +		cfg->bits_per_sample = mcfg->bit_width == 24 ? 32 : mcfg->bit_width;
>  		cfg->q_factor = mcfg->bit_width - 1;
>  		cfg->endianness = PCM_LITTLE_ENDIAN;
>  		cfg->num_channels = mcfg->num_channels;
>