[PATCH 3/5] ASoC: soc-pcm: Apply snd_soc_dai_link_ch_map.codec_ch_mask to codec params

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

In __soc_pcm_hw_params() if there is a snd_soc_dai_link_ch_map with
non-zero codec_ch_mask, use that channel mask to restrict which channels
are enabled on the codec. But only if there isn't a TDM mask.

It is possible that a snd_soc_dai_link_ch_map could include the same codec
multiple times on different CPUs so the for_each_rtd_ch_maps() loop
accumulates the channel masks for all entries of that codec.

If a TDM mask was also set, it takes priority and is used instead of any
possible snd_soc_dai_link_ch_map entries. (They cannot be ANDed together
because the bit positions are indicating different things: TDM is a bit
for each TDM slot, codec_ch_mask is a bit for each codec channel.)

This fixes a problem of incorrect TX channels enabled on the codec when
multiple codecs are aggregated on a single capture link. For example:

- Two CPUs with six 4-channel codecs.
- The machine driver chooses to assign one channel from each codec to
  one channel on the CPU
- But the codec hw_params() would be passed a channel count of 6, which
  (a) is more channels than the codec has and (b) allows enabling channels
  that should not be driving the audio bus.

Fixes: ac950278b087 ("ASoC: add N cpus to M codecs dai link support")
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
 sound/soc/soc-pcm.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index cb64ced21149..3137c091bdb8 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -1206,7 +1206,9 @@ static int __soc_pcm_hw_params(struct snd_pcm_substream *substream,
 		goto out;
 
 	for_each_rtd_codec_dais(rtd, i, codec_dai) {
-		unsigned int tdm_mask = snd_soc_dai_tdm_mask_get(codec_dai, substream->stream);
+		unsigned int ch_mask = snd_soc_dai_tdm_mask_get(codec_dai, substream->stream);
+		struct snd_soc_dai_link_ch_map *ch_maps;
+		int j;
 
 		/*
 		 * Skip CODECs which don't support the current stream type,
@@ -1228,9 +1230,15 @@ static int __soc_pcm_hw_params(struct snd_pcm_substream *substream,
 		/* copy params for each codec */
 		tmp_params = *params;
 
-		/* fixup params based on TDM slot masks */
-		if (tdm_mask)
-			soc_pcm_codec_params_fixup(&tmp_params, tdm_mask);
+		/* fixup params based on TDM or ch_map masks */
+		if (!ch_mask) {
+			for_each_rtd_ch_maps(rtd, j, ch_maps)
+				if (ch_maps->codec == i)
+					ch_mask |= ch_maps->codec_ch_mask;
+		}
+
+		if (ch_mask)
+			soc_pcm_codec_params_fixup(&tmp_params, ch_mask);
 
 		ret = snd_soc_dai_hw_params(codec_dai, substream,
 					    &tmp_params);
-- 
2.47.3