Re: [PATCH v2 19/24] ASoC: SOF: ipc4-topology: Set FAST_MODE for host copier in compr mode

[Pierre-Louis Bossart <pierre-louis.bossart@linux.dev>]

On 9/9/26 11:09, Peter Ujfalusi wrote:
> FAST_MODE allows the host DMA to work in opportunistic, free running mode,
> which matches with the bitstream nature of compressed devices.

Does it?

My memory of the 'opportunistic' behavior was that the DMA would try to
use every possible window to send to/from the DSP, so that the bus would
be idle for longer periods of time overall.

That would make sense as well for PCM, no?

Maybe this is the right thing to do for compressed data, I just wonder
why it is NOT the right thing to do for PCM...

> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
> Reviewed-by: Liam Girdwood <liam.r.girdwood@intel.com>
> ---
>  sound/soc/sof/ipc4-topology.c | 3 +++
>  sound/soc/sof/ipc4-topology.h | 5 +++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/sound/soc/sof/ipc4-topology.c b/sound/soc/sof/ipc4-topology.c
> index 42cf444e847e..566913025cc7 100644
> --- a/sound/soc/sof/ipc4-topology.c
> +++ b/sound/soc/sof/ipc4-topology.c
> @@ -744,6 +744,9 @@ static int sof_ipc4_widget_setup_pcm(struct snd_sof_widget *swidget)
>  			sps->dsp_max_burst_size_in_ms = 1;
>  	}
>  
> +	if (spcm->pcm.compress)
> +		ipc4_copier->data.copier_feature_mask |= BIT(SOF_IPC4_COPIER_FAST_MODE);
> +
>  skip_gtw_cfg:
>  	ipc4_copier->gtw_attr = kzalloc_obj(*ipc4_copier->gtw_attr);
>  	if (!ipc4_copier->gtw_attr) {
> diff --git a/sound/soc/sof/ipc4-topology.h b/sound/soc/sof/ipc4-topology.h
> index 5e78f3de092e..c2949ff979a5 100644
> --- a/sound/soc/sof/ipc4-topology.h
> +++ b/sound/soc/sof/ipc4-topology.h
> @@ -222,6 +222,11 @@ struct sof_copier_gateway_cfg {
>  	uint32_t config_data[];
>  };
>  
> +/* bit definition in copier_feature_mask */
> +enum sof_ipc4_copier_feature {
> +	SOF_IPC4_COPIER_FAST_MODE = 0, /* free running mode of host copier */
> +};
> +
>  /**
>   * struct sof_ipc4_copier_data - IPC data for copier
>   * @base_config: Base configuration including input audio format