[PATCH 4/5] ASoC: sdw_utils: Set snd_soc_dai_link_ch_map.codec_ch_mask for capture

[Richard Fitzgerald <rf@opensource.cirrus.com>]

In asoc_sdw_hw_params() set the codec_ch_mask member of struct
snd_soc_dai_link_ch_map for capture streams. ASoC will then pass the
correct number of channels to each codec hw_params(). This prevents
trying to enable more channels on the codec DP than have been allocated
bitslots in the SoundWire frame, which would cause bus clash errors.

In theory codec_ch_mask could also be set for playback streams, but for
those the CPU is the only sender so there is no risk of bus clash.
For playback streams codec_ch_mask is set to 0 to preserve the existing
behavior and avoid introducing bugs.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
 sound/soc/sdw_utils/soc_sdw_utils.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/sound/soc/sdw_utils/soc_sdw_utils.c b/sound/soc/sdw_utils/soc_sdw_utils.c
index cab1578b893d..778ba6531434 100644
--- a/sound/soc/sdw_utils/soc_sdw_utils.c
+++ b/sound/soc/sdw_utils/soc_sdw_utils.c
@@ -1731,7 +1731,7 @@ int asoc_sdw_hw_params(struct snd_pcm_substream *substream,
 	struct snd_soc_pcm_runtime *rtd = snd_soc_substream_to_rtd(substream);
 	struct snd_soc_dai_link_ch_map *ch_maps;
 	int ch = params_channels(params);
-	unsigned int ch_mask;
+	unsigned int cpu_ch_mask, codec_ch_mask;
 	int num_codecs;
 	int step;
 	int i;
@@ -1741,8 +1741,9 @@ int asoc_sdw_hw_params(struct snd_pcm_substream *substream,
 
 	/* Identical data will be sent to all codecs in playback */
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
-		ch_mask = GENMASK(ch - 1, 0);
+		cpu_ch_mask = GENMASK(ch - 1, 0);
 		step = 0;
+		codec_ch_mask = 0;
 	} else {
 		num_codecs = rtd->dai_link->num_codecs;
 
@@ -1752,17 +1753,24 @@ int asoc_sdw_hw_params(struct snd_pcm_substream *substream,
 			return -EINVAL;
 		}
 
-		ch_mask = GENMASK(ch / num_codecs - 1, 0);
-		step = hweight_long(ch_mask);
+		cpu_ch_mask = GENMASK(ch / num_codecs - 1, 0);
+		step = hweight_long(cpu_ch_mask);
+		codec_ch_mask = cpu_ch_mask;
 	}
 
 	/*
 	 * The captured data will be combined from each cpu DAI if the dai
 	 * link has more than one codec DAIs. Set codec channel mask and
 	 * ASoC will set the corresponding channel numbers for each cpu dai.
+	 *
+	 * sdw_stream_add_slave() assigns different payload offsets to each
+	 * codec in a capture stream, so that the same channels on each
+	 * codec map to different channels on the CPU.
 	 */
-	for_each_link_ch_maps(rtd->dai_link, i, ch_maps)
-		ch_maps->cpu_ch_mask = ch_mask << (i * step);
+	for_each_link_ch_maps(rtd->dai_link, i, ch_maps) {
+		ch_maps->cpu_ch_mask = cpu_ch_mask << (i * step);
+		ch_maps->codec_ch_mask = codec_ch_mask;
+	}
 
 	return 0;
 }
-- 
2.47.3