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

[Christian Hewitt <christianshewitt@gmail.com>]

> On 20 Jan 2026, at 4:52 pm, Cristian Ciocaltea <cristian.ciocaltea@collabora.com> wrote:
> 
> Hi Christian,
> 
> On 12/6/25 9:27 AM, Christian Hewitt wrote:
>> From: Jonas Karlman <jonas@kwiboo.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@gmail.com>
>> Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Christian Hewitt <christianshewitt@gmail.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@collabora.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