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

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Message-ID: <d7121d00-4353-2901-e87b-7fef7da5a35f@axis.com>
Date: Fri, 15 Nov 2024 13:25:00 +0100
From: Stefan Ekenberg <stefan.ekenberg@...s.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: 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>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 kernel@...s.com
Subject: Re: [PATCH] drm/bridge: adv7511_audio: Update Audio InfoFrame
 properly

On 11/15/24 09:16, Dmitry Baryshkov wrote:
> On Wed, Nov 13, 2024 at 08:38:11AM +0100, Stefan Ekenberg wrote:
>> 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.
>>
>> Signed-off-by: Stefan Ekenberg <stefan.ekenberg@...s.com>
> 
> Missing Fixes tag,

Ok, I will add Fixes tag.

> 
>> ---
>>   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);
> 
> Should the REG_GC(1) still be written?

The comment before this line states "use Audio infoframe updated info" 
and, before my change, bit 5 of REG_GC(1) was cleared by the line I 
removed. Bit 5 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 actually meant to clear bit 5 
of REG_INFOFRAME_UPDATE from the very beginning. In short, clearing bit 
5 of REG_GC(1) is invalid since it is a read-only field.

> 
>> +
>>   	/* 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>
>>
>