linux-kernel - [PATCH v3] drm/bridge: adv7511_audio: Update Audio InfoFrame properly

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Message-ID: <20241118-adv7511-audio-info-frame-v3-1-31edd9931856@axis.com>
Date: Mon, 18 Nov 2024 09:03:33 +0100
From: Stefan Ekenberg <stefan.ekenberg@...s.com>
To: Andrzej Hajda <andrzej.hajda@...el.com>, Neil Armstrong
	<neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, Laurent Pinchart
	<Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, "Jernej
 Skrabec" <jernej.skrabec@...il.com>, Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>
CC: <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
	<kernel@...s.com>, Stefan Ekenberg <stefan.ekenberg@...s.com>
Subject: [PATCH v3] drm/bridge: adv7511_audio: Update Audio InfoFrame
 properly

AUDIO_UPDATE bit (Bit 5 of MAIN register 0x4A) needs to be set to 1
while updating Audio InfoFrame information and then set to 0 when done.
Otherwise partially updated Audio InfoFrames could be sent out. Two
cases where this rule were not followed are fixed:
 - In adv7511_hdmi_hw_params() make sure AUDIO_UPDATE bit is updated
   before/after setting ADV7511_REG_AUDIO_INFOFRAME.
 - In audio_startup() use the correct register for clearing
   AUDIO_UPDATE bit.

The problem with corrupted audio infoframes were discovered by letting
a HDMI logic analyser check the output of ADV7535.

Note that this patchs replaces writing REG_GC(1) with
REG_INFOFRAME_UPDATE. Bit 5 of REG_GC(1) is positioned within field
GC_PP[3:0] and that field doesn't control audio infoframe and is read-
only. My conclusion therefore was that the author if this code meant to
clear bit 5 of REG_INFOFRAME_UPDATE from the very beginning.

Fixes: 53c515befe28 ("drm/bridge: adv7511: Add Audio support")
Signed-off-by: Stefan Ekenberg <stefan.ekenberg@...s.com>
---
Changes in v3:
- Extend commit message and explain replacement of REG_GC(1)
- Link to v2: https://lore.kernel.org/r/20241115-adv7511-audio-info-frame-v2-1-ca4793ef3a91@axis.com

Changes in v2:
- Add Fixes tag
- Link to v1: https://lore.kernel.org/r/20241113-adv7511-audio-info-frame-v1-1-49b368b995a5@axis.com
---
 drivers/gpu/drm/bridge/adv7511/adv7511_audio.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_audio.c b/drivers/gpu/drm/bridge/adv7511/adv7511_audio.c
index 61f4a38e7d2bf6905683cbc9e762b28ecc999d05..8f786592143b6c81e5a434768b51508d5e5f3c73 100644
--- a/drivers/gpu/drm/bridge/adv7511/adv7511_audio.c
+++ b/drivers/gpu/drm/bridge/adv7511/adv7511_audio.c
@@ -153,7 +153,16 @@ static int adv7511_hdmi_hw_params(struct device *dev, void *data,
 			   ADV7511_AUDIO_CFG3_LEN_MASK, len);
 	regmap_update_bits(adv7511->regmap, ADV7511_REG_I2C_FREQ_ID_CFG,
 			   ADV7511_I2C_FREQ_ID_CFG_RATE_MASK, rate << 4);
-	regmap_write(adv7511->regmap, 0x73, 0x1);
+
+	/* send current Audio infoframe values while updating */
+	regmap_update_bits(adv7511->regmap, ADV7511_REG_INFOFRAME_UPDATE,
+			   BIT(5), BIT(5));
+
+	regmap_write(adv7511->regmap, ADV7511_REG_AUDIO_INFOFRAME(0), 0x1);
+
+	/* use Audio infoframe updated info */
+	regmap_update_bits(adv7511->regmap, ADV7511_REG_INFOFRAME_UPDATE,
+			   BIT(5), 0);
 
 	return 0;
 }
@@ -184,8 +193,9 @@ static int audio_startup(struct device *dev, void *data)
 	regmap_update_bits(adv7511->regmap, ADV7511_REG_GC(0),
 				BIT(7) | BIT(6), BIT(7));
 	/* use Audio infoframe updated info */
-	regmap_update_bits(adv7511->regmap, ADV7511_REG_GC(1),
+	regmap_update_bits(adv7511->regmap, ADV7511_REG_INFOFRAME_UPDATE,
 				BIT(5), 0);
+
 	/* enable SPDIF receiver */
 	if (adv7511->audio_source == ADV7511_AUDIO_SOURCE_SPDIF)
 		regmap_update_bits(adv7511->regmap, ADV7511_REG_AUDIO_CONFIG,

---
base-commit: 59b723cd2adbac2a34fc8e12c74ae26ae45bf230
change-id: 20241108-adv7511-audio-info-frame-54614dd4bf57

Best regards,
-- 
Stefan Ekenberg <stefan.ekenberg@...s.com>