[alsa-devel] [PATCH] ASoC: msm8916-wcd-digital: Reset RX interpolation path after use

[Stephan Gerhold]

For some reason, attempting to route audio through QDSP6 on MSM8916
causes the RX interpolation path to get "stuck" after playing audio
a few times. In this situation, the analog codec part is still working,
but the RX path in the digital codec stops working, so you only hear
the analog parts powering up. After a reboot everything works again.

So far I was not able to reproduce the problem when using lpass-cpu.

The downstream kernel driver avoids this by resetting the RX
interpolation path after use. In mainline we do something similar
for the TX decimator (LPASS_CDC_CLK_TX_RESET_B1_CTL), but the
interpolator reset (LPASS_CDC_CLK_RX_RESET_CTL) got lost when the
msm8916-wcd driver was split into analog and digital.

Fix this problem by adding the reset to
msm8916_wcd_digital_enable_interpolator().

Fixes: 150db8c5afa1 ("ASoC: codecs: Add msm8916-wcd digital codec")
Cc: Srinivas Kandagatla <srinivas.kandagatla at linaro.org>
Signed-off-by: Stephan Gerhold <stephan at gerhold.net>
---
Tested on msm8916-samsung-a5u:
  - qdsp6 does no longer stop working after playing audio a few times
  - lpass-cpu is still working fine (no difference)
---
 sound/soc/codecs/msm8916-wcd-digital.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sound/soc/codecs/msm8916-wcd-digital.c b/sound/soc/codecs/msm8916-wcd-digital.c
index 58b2468fb2a7..09fccacadd6b 100644
--- a/sound/soc/codecs/msm8916-wcd-digital.c
+++ b/sound/soc/codecs/msm8916-wcd-digital.c
@@ -586,6 +586,12 @@ static int msm8916_wcd_digital_enable_interpolator(
 		snd_soc_component_write(component, rx_gain_reg[w->shift],
 			      snd_soc_component_read32(component, rx_gain_reg[w->shift]));
 		break;
+	case SND_SOC_DAPM_POST_PMD:
+		snd_soc_component_update_bits(component, LPASS_CDC_CLK_RX_RESET_CTL,
+					      1 << w->shift, 1 << w->shift);
+		snd_soc_component_update_bits(component, LPASS_CDC_CLK_RX_RESET_CTL,
+					      1 << w->shift, 0x0);
+		break;
 	}
 	return 0;
 }
-- 
2.24.1