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

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Message-ID: <CAA8EJpqbMvevmWZ3AbQOwBbVUOkUPHB_mrv+BtLndAcpLmcVpA@mail.gmail.com>
Date: Fri, 15 Nov 2024 21:49:03 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Stefan Ekenberg <stefan.ekenberg@...s.com>
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 Fri, 15 Nov 2024 at 14:25, Stefan Ekenberg <stefan.ekenberg@...s.com> wrote:
>
> 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.

Ack, thanks for the explanation. It might be nice if you can include
this into the commit message.

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


-- 
With best wishes
Dmitry