linux-kernel - Re: [PATCH] drm/bridge: dw-hdmi-qp: fix multi-channel audio output

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Message-Id: <021065E9-53DE-40DC-B6FB-CC0AE272FAAE@gmail.com>
Date: Tue, 20 Jan 2026 17:31:22 +0400
From: Christian Hewitt <christianshewitt@...il.com>
To: Cristian Ciocaltea <cristian.ciocaltea@...labora.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>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
 Detlev Casanova <detlev.casanova@...labora.com>,
 Douglas Anderson <dianders@...omium.org>,
 Andy Yan <andy.yan@...k-chips.com>,
 Sugar Zhang <sugar.zhang@...k-chips.com>,
 Luca Ceresoli <luca.ceresoli@...tlin.com>,
 Heiko Stuebner <heiko@...ech.de>,
 dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/bridge: dw-hdmi-qp: fix multi-channel audio output

> On 20 Jan 2026, at 4:52 pm, Cristian Ciocaltea <cristian.ciocaltea@...labora.com> wrote:
> 
> Hi Christian,
> 
> On 12/6/25 9:27 AM, Christian Hewitt wrote:
>> From: Jonas Karlman <jonas@...boo.se>
>> 
>> Channel Allocation (PB4) and Level Shift Information (PB5) are
>> configured with values from PB1 and PB2 due to the wrong offset
>> being used. This results in missing audio channels or incorrect
>> speaker placement when playing multi-channel audio.
>> 
>> Use the correct offset to fix multi-channel audio output.
>> 
>> Fixes: fd0141d1a8a2 ("drm/bridge: synopsys: Add audio support for dw-hdmi-qp")
>> Reported-by: Christian Hewitt <christianshewitt@...il.com>
>> Signed-off-by: Jonas Karlman <jonas@...boo.se>
Signed-off-by: Christian Hewitt <christianshewitt@...il.com>

>> ---
>> buffer is a pointer to u8 while data written to PKT_AUDI_CONTENTS
>> is u32, so buffer contains audio infoframe header (buffer[0:2]) +
>> checksum (buffer[3]) + payload byte 1-10 (buffer[4:13]), e.g.
>> 
>> regmap_bulk_write(hdmi->regm, PKT_AUDI_CONTENTS1, &buffer[3], 1)
>> .. will write PB0-PB3 to AUDI_CONTENTS1
>> 
>> regmap_bulk_write(hdmi->regm, PKT_AUDI_CONTENTS2, &buffer[4], 1)
>> .. will write PB1-PB4 to AUDI_CONTENTS2, but should be PB4-PB7
>> 
>> &buffer[4] will point to payload byte 4 not payload byte 1, due
>> to u8/u32 and not considering the size of header+checksum (3+1).
>> ---
>> drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
>> index f3a13da488e6..7b8a69383dc4 100644
>> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
>> @@ -845,7 +845,7 @@ static int dw_hdmi_qp_config_audio_infoframe(struct dw_hdmi_qp *hdmi,
>> 
>> regmap_bulk_write(hdmi->regm, PKT_AUDI_CONTENTS0, &header_bytes, 1);
>> regmap_bulk_write(hdmi->regm, PKT_AUDI_CONTENTS1, &buffer[3], 1);
>> - regmap_bulk_write(hdmi->regm, PKT_AUDI_CONTENTS2, &buffer[4], 1);
>> + regmap_bulk_write(hdmi->regm, PKT_AUDI_CONTENTS2, &buffer[7], 1);
> 
> Since making use of regmap_bulk_write(), this could be further optimized as:
> 
> -       regmap_bulk_write(hdmi->regm, PKT_AUDI_CONTENTS1, &buffer[3], 1);
> -       regmap_bulk_write(hdmi->regm, PKT_AUDI_CONTENTS2, &buffer[4], 1);
> +       regmap_bulk_write(hdmi->regm, PKT_AUDI_CONTENTS1, &buffer[3], 2);
> 
> Regardless,
> 
> Reviewed-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
> 
> Please note you also need to provide your SoB, check "Sign your work ..."
> section in [1].

Ahh, I was hoping to just forward Jonas’ patch. If it’s possible to
apply the SoB above when merging, please do. If not I can send a v2
series (someone let me know).

Christian

> Regards,
> Cristian
> 
> [1] https://www.kernel.org/doc/Documentation/process/submitting-patches.rst