[PATCH v2 2/2] drm/bridge: it6505: Don't reject audio hw_params without an encoder

[Daniel Golle]

it6505_audio_setup_hw_params() returns -ENODEV when the bridge is not
attached to a DRM encoder. Now that it6505 registers an hdmi-audio-codec,
this callback runs whenever a stream is configured on the I2S DAI it is
wired to, including when that DAI is shared with another codec. On
mt8186-corsola the speaker amplifier (rt1019) and it6505 share I2S3, so
when the it6505 DP output has no display attached (bridge.encoder is
NULL) the -ENODEV propagates up through dpcm_be_dai_hw_params() and tears
down the whole backend, breaking speaker playback.

The check is harmful in its own right: the rest of the function only
caches the stream parameters (channel count, rate, word length) in
software, none of which needs an encoder. Returning early leaves
it6505->audio.channel_count at 0, which would then index
audio_info_ca[-1] in it6505_enable_audio_infoframe() should a display be
hotplugged while a stream is running, and makes such a hotplug play with
stale parameters.

Drop the encoder check so the parameters are always cached; the actual
audio output is already gated by it6505->powered.

Fixes: b5c84a9edcd4 ("drm/bridge: add it6505 driver")
Signed-off-by: Daniel Golle <daniel@xxxxxxxxxxxxxx>
---
v2:
 * drop the encoder check entirely instead of returning 0 early, so
   the stream parameters are always cached even while no display is
   attached; rewrite the commit message to explain why the check is
   harmful

 drivers/gpu/drm/bridge/ite-it6505.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
index d84441926e8e..e20edbbb7c13 100644
--- a/drivers/gpu/drm/bridge/ite-it6505.c
+++ b/drivers/gpu/drm/bridge/ite-it6505.c
@@ -2979,9 +2979,6 @@ static int it6505_audio_setup_hw_params(struct it6505 *it6505,
 			     params->sample_rate, params->sample_width,
 			     params->cea.channels);
 
-	if (!it6505->bridge.encoder)
-		return -ENODEV;
-
 	if (params->cea.channels <= 1 || params->cea.channels > 8) {
 		DRM_DEV_DEBUG_DRIVER(dev, "channel number: %d not support",
 				     it6505->audio.channel_count);
-- 
2.55.0