Re: [RFC] ASoC: soc-pcm: Use conditional PCM hardware parameter initialization

["Péter Ujfalusi" <peter.ujfalusi@linux.intel.com>]

On 20/10/2025 10:37, Peter Ujfalusi wrote:
> Component drivers can prepare snd_pcm_hardware struct based on the hardware
> capabilities which information should not be discarded.
> 
> Only touch the rates, channels_max and formats if they were left to 0,
> otherwise keep the provided configuration intact for the parameter cross
> checking decision.
> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
> ---
> Hi,
> 
> this patch in essence extends the special casing of formats done by
> 083a25b18d6a ("ASoC: soc-pcm: fix hw->formats cleared by soc_pcm_hw_init() for dpcm")
> 
> Other parameters might have been set in the same way as the formats
> and preserving these are equally important.
> 
> A case for this is SOF used with HDA codec (analog or more importantly, HDMI)
> where the hw-> params are set based on the connected display/device and
> should be preserved so we can report correct rate, format and channels
> supported by the equipment.
> 
> If the hw-> parameters are left uninitialized then we still need to
> set the UINT/ULLONG_MAX for the refining code to work.
> 
> This applies only for FE setup, in other cases we shall (as before) do
> a full re-initialization.
> 
> I think this makes sense and I cannot think where this might flop, but
> sent as RFC to see what people think. 
> 
> Br,
> Peter
> 
> 
>  sound/soc/soc-pcm.c | 39 ++++++++++++++++++++++++++-------------
>  1 file changed, 26 insertions(+), 13 deletions(-)
> 
> diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
> index 2c21fd528afd..e4bbcf4bcc9d 100644
> --- a/sound/soc/soc-pcm.c
> +++ b/sound/soc/soc-pcm.c
> @@ -570,14 +570,31 @@ static void soc_pcm_apply_msb(struct snd_pcm_substream *substream)
>  	soc_pcm_set_msb(substream, cpu_bits);
>  }
>  
> -static void soc_pcm_hw_init(struct snd_pcm_hardware *hw)
> +static void soc_pcm_hw_init(struct snd_pcm_hardware *hw, bool preserve_config)
>  {
> -	hw->rates		= UINT_MAX;
> -	hw->rate_min		= 0;
> -	hw->rate_max		= UINT_MAX;
> -	hw->channels_min	= 0;
> -	hw->channels_max	= UINT_MAX;
> -	hw->formats		= ULLONG_MAX;
> +	if (preserve_config) {
> +		/*
> +		 * preserve the configuration which might be done by components
> +		 * Note: if the rates/rate_max/channels_max/formats are left to
> +		 * 0 we still need to initialize them for the parameter updates
> +		 * to work
> +		 */
> +		if (!hw->rates)
> +			hw->rates = UINT_MAX;
> +		if (!hw->rate_max)
> +			hw->rate_max = UINT_MAX;
> +		if (!hw->channels_max)
> +			hw->channels_max = UINT_MAX;
> +		if (!hw->formats)
> +			hw->formats = ULLONG_MAX;
> +	} else {
> +		hw->rates = UINT_MAX;
> +		hw->rate_min = 0;
> +		hw->rate_max = UINT_MAX;
> +		hw->channels_min = 0;
> +		hw->channels_max = UINT_MAX;
> +		hw->formats = ULLONG_MAX;
> +	}
>  }
>  
>  static void soc_pcm_hw_update_rate(struct snd_pcm_hardware *hw,
> @@ -626,7 +643,7 @@ int snd_soc_runtime_calc_hw(struct snd_soc_pcm_runtime *rtd,
>  	unsigned int cpu_chan_min = 0, cpu_chan_max = UINT_MAX;
>  	int i;
>  
> -	soc_pcm_hw_init(hw);
> +	soc_pcm_hw_init(hw, false);
>  
>  	/* first calculate min/max only for CPUs in the DAI link */
>  	for_each_rtd_cpu_dais(rtd, i, cpu_dai) {
> @@ -1738,13 +1755,9 @@ static void dpcm_runtime_setup_fe(struct snd_pcm_substream *substream)
>  	struct snd_pcm_hardware *hw = &runtime->hw;
>  	struct snd_soc_dai *dai;
>  	int stream = substream->stream;
> -	u64 formats = hw->formats;
>  	int i;
>  
> -	soc_pcm_hw_init(hw);
> -
> -	if (formats)
> -		hw->formats &= formats;
> +	soc_pcm_hw_init(hw, true);

Instead of changing the soc_pcm_hw_init() it might be better to move the
relevant implementation inline here. I will do this for the patch.

>  
>  	for_each_rtd_cpu_dais(fe, i, dai) {
>  		const struct snd_soc_pcm_stream *cpu_stream;

-- 
Péter