When using multiple codecs, at most one codec should generate the master clock. All codecs except the first are therefore configured for slave mode. Before this patch all codecs in a multicodec setup had to be slaves. This is needed when e.g., connecting multiple sound hats for simultaneous playback to the raspberry pi I2S output and one of the sound hats generates the I2S clocks (https://github.com/raspberrypi/linux/pull/3337).

I checked the raspberry pi kernel tree for multicodec usage with `fgrep num_codecs -R sound/soc/` and verified that all existing multicodec drivers with hardcoded format have indeed configured all codecs for slave mode. Doing a similar check on the current for-5.5 tree is more difficult since .num_codecs is now hidden behind a preprocessor macro.

Signed-off-by: Johannes Krude johannes@krude.de --- sound/soc/soc-core.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c index 058e038df..cb8952527 100644 --- a/sound/soc/soc-core.c +++ b/sound/soc/soc-core.c @@ -1688,6 +1688,14 @@ int snd_soc_runtime_set_dai_fmt(struct snd_soc_pcm_runtime *rtd,

for_each_rtd_codec_dai(rtd, i, codec_dai) { + unsigned int codec_dai_fmt = dai_fmt; + - ret = snd_soc_dai_set_fmt(codec_dai, dai_fmt); + // there can only be one master when using multiple codecs + if (i && (codec_dai_fmt & SND_SOC_DAIFMT_MASTER_MASK)) { + codec_dai_fmt &= ~SND_SOC_DAIFMT_MASTER_MASK; + codec_dai_fmt |= SND_SOC_DAIFMT_CBS_CFS; + } + + ret = snd_soc_dai_set_fmt(codec_dai, codec_dai_fmt); if (ret != 0 && ret != -ENOTSUPP) { dev_warn(codec_dai->dev, "ASoC: Failed to set DAI format: %d\n", ret);