linux-kernel - Re: [PATCH] drm/msm: update the high bitfield of certain DSI registers

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Message-ID: <74e3836e-af29-4b5f-b644-23bdff084c78@oss.qualcomm.com>
Date: Wed, 30 Jul 2025 14:45:13 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Ayushi Makhija <quic_amakhija@...cinc.com>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Cc: robdclark@...il.com, lumag@...nel.org, sean@...rly.run,
        marijn.suijten@...ainline.org, airlied@...il.com, simona@...ll.ch,
        quic_rajeevny@...cinc.com, quic_vproddut@...cinc.com,
        quic_jesszhan@...cinc.com
Subject: Re: [PATCH] drm/msm: update the high bitfield of certain DSI
 registers

On 7/30/25 2:39 PM, Ayushi Makhija wrote:
> Currently, the high bitfield of certain DSI registers
> do not align with the configuration of the SWI registers
> description. This can lead to wrong programming these DSI
> registers, for example for 4k resloution where H_TOTAL is
> taking 13 bits but software is programming only 12 bits
> because of the incorrect bitmask for H_TOTAL bitfeild,
> this is causing DSI FIFO errors. To resolve this issue,
> increase the high bitfield of the DSI registers from 12 bits
> to 16 bits in dsi.xml to match the SWI register configuration.
> 
> Signed-off-by: Ayushi Makhija <quic_amakhija@...cinc.com>
> ---
>  drivers/gpu/drm/msm/registers/display/dsi.xml | 28 +++++++++----------
>  1 file changed, 14 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/registers/display/dsi.xml b/drivers/gpu/drm/msm/registers/display/dsi.xml
> index 501ffc585a9f..c7a7b633d747 100644
> --- a/drivers/gpu/drm/msm/registers/display/dsi.xml
> +++ b/drivers/gpu/drm/msm/registers/display/dsi.xml
> @@ -159,28 +159,28 @@ xsi:schemaLocation="https://gitlab.freedesktop.org/freedreno/ rules-fd.xsd">
>  		<bitfield name="RGB_SWAP" low="12" high="14" type="dsi_rgb_swap"/>
>  	</reg32>
>  	<reg32 offset="0x00020" name="ACTIVE_H">
> -		<bitfield name="START" low="0" high="11" type="uint"/>
> -		<bitfield name="END" low="16" high="27" type="uint"/>
> +		<bitfield name="START" low="0" high="15" type="uint"/>
> +		<bitfield name="END" low="16" high="31" type="uint"/>
>  	</reg32>
>  	<reg32 offset="0x00024" name="ACTIVE_V">
> -		<bitfield name="START" low="0" high="11" type="uint"/>
> -		<bitfield name="END" low="16" high="27" type="uint"/>
> +		<bitfield name="START" low="0" high="15" type="uint"/>
> +		<bitfield name="END" low="16" high="31" type="uint"/>
>  	</reg32>
>  	<reg32 offset="0x00028" name="TOTAL">
> -		<bitfield name="H_TOTAL" low="0" high="11" type="uint"/>
> -		<bitfield name="V_TOTAL" low="16" high="27" type="uint"/>
> +		<bitfield name="H_TOTAL" low="0" high="15" type="uint"/>
> +		<bitfield name="V_TOTAL" low="16" high="31" type="uint"/>
>  	</reg32>
>  	<reg32 offset="0x0002c" name="ACTIVE_HSYNC">
> -		<bitfield name="START" low="0" high="11" type="uint"/>
> -		<bitfield name="END" low="16" high="27" type="uint"/>
> +		<bitfield name="START" low="0" high="15" type="uint"/>
> +		<bitfield name="END" low="16" high="31" type="uint"/>
>  	</reg32>
>  	<reg32 offset="0x00030" name="ACTIVE_VSYNC_HPOS">
> -		<bitfield name="START" low="0" high="11" type="uint"/>
> -		<bitfield name="END" low="16" high="27" type="uint"/>
> +		<bitfield name="START" low="0" high="15" type="uint"/>
> +		<bitfield name="END" low="16" high="31" type="uint"/>
>  	</reg32>
>  	<reg32 offset="0x00034" name="ACTIVE_VSYNC_VPOS">

FWIW looks like at least on 8280, ACTIVE_VSYNC_HPOS offset = 0x38
and HPOS doesn't exist

Konrad