[PATCH 3/4] ASoC: mediatek: mt8188: Constrain UL8 FE to its back end's capabilities

[Michał Kopeć]

UL8 advertises up to 24 channels, but its only back end, ETDM1_IN,
supports at most 16, and its bit clock is limited to 24.576 MHz.
Without merged constraints, userspace can open UL8 with 48 kHz, 24
channels and 32-bit slots, which then fails in hw_params:

  mtk_dai_etdm_configure bck rate 36864000 not support
  ASoC error (-22): at snd_soc_dai_hw_params() on ETDM1_IN

Set dpcm_merged_chan/rate/format, as the DL front ends already do, so
the FE only offers configurations the back end can accept.

Fixes: 96035d46d4b4 ("ASoC: mediatek: mt8188: add machine driver with mt6359")
Signed-off-by: Michał Kopeć <michal@nozomi.space>
---
 sound/soc/mediatek/mt8188/mt8188-mt6359.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/soc/mediatek/mt8188/mt8188-mt6359.c b/sound/soc/mediatek/mt8188/mt8188-mt6359.c
index 75c90d1d165f7..f07aeb6371083 100644
--- a/sound/soc/mediatek/mt8188/mt8188-mt6359.c
+++ b/sound/soc/mediatek/mt8188/mt8188-mt6359.c
@@ -1142,6 +1142,9 @@ static struct snd_soc_dai_link mt8188_mt6359_dai_links[] = {
 		},
 		.dynamic = 1,
 		.capture_only = 1,
+		.dpcm_merged_chan = 1,
+		.dpcm_merged_rate = 1,
+		.dpcm_merged_format = 1,
 		SND_SOC_DAILINK_REG(capture8),
 	},
 	[DAI_LINK_UL9_FE] = {
-- 
2.55.0