[PATCH 2/3] ASoC: es8316: Do not set rate constraints for unsupported MCLKs

[Cristian Ciocaltea <cristian.ciocaltea@collabora.com>]

When using the codec through the generic audio graph card, there are at
least two calls of es8316_set_dai_sysclk(), with the effect of limiting
the allowed sample rates according to the MCLK/LRCK ratios supported by
the codec:

1. During audio card setup, to set the initial MCLK - see
   asoc_simple_init_dai().

2. Before opening a stream, to update MCLK, according to the stream
   sample rate and the multiplication factor - see
   asoc_simple_hw_params().

In some cases the initial MCLK might be set to a frequency that doesn't
match any of the supported ratios, e.g. 12287999 instead of 12288000,
which is only 1 Hz below the supported clock, as that is what the
hardware reports. This creates an empty list of rate constraints, which
is further passed to snd_pcm_hw_constraint_list() via
es8316_pcm_startup(), and causes the following error on the very first
access of the sound card:

  $ speaker-test -D hw:Analog,0 -F S16_LE -c 2 -t wav
  Broken configuration for playback: no configurations available: Invalid argument
  Setting of hwparams failed: Invalid argument

Note that all subsequent retries succeed thanks to the updated MCLK set
at point 2 above, which uses a computed frequency value instead of a
reading from the hardware registers. Normally this would have mitigated
the issue, but es8316_pcm_startup() executes before the 2nd call to
es8316_set_dai_sysclk(), hence it cannot make use of the updated
constraints.

Since es8316_pcm_hw_params() performs anyway a final validation of MCLK
against the stream sample rate and the supported MCLK/LRCK ratios, fix
the issue by ensuring that sysclk_constraints list is only set when at
least one supported sample rate is autodetected by the codec.

Fixes: b8b88b70875a ("ASoC: add es8316 codec driver")
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
---
 sound/soc/codecs/es8316.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/soc/codecs/es8316.c b/sound/soc/codecs/es8316.c
index 773c94fd3547..a78c0049a30c 100644
--- a/sound/soc/codecs/es8316.c
+++ b/sound/soc/codecs/es8316.c
@@ -386,7 +386,7 @@ static int es8316_set_dai_sysclk(struct snd_soc_dai *codec_dai,
 			es8316->allowed_rates[count++] = freq / ratio;
 	}
 
-	es8316->sysclk_constraints.list = es8316->allowed_rates;
+	es8316->sysclk_constraints.list = count ? es8316->allowed_rates : NULL;
 	es8316->sysclk_constraints.count = count;
 
 	return 0;
-- 
2.40.1