linux-kernel - Re: [PATCH v2 3/3] drm/msm/dpu: Remove arbitrary limit of 1 interface in DSC topology

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Message-ID: <a3374b07-11a0-4eec-9f57-3ca25068fe24@quicinc.com>
Date: Mon, 10 Feb 2025 17:54:24 -0800
From: Jessica Zhang <quic_jesszhan@...cinc.com>
To: Marijn Suijten <marijn.suijten@...ainline.org>,
        Rob Clark
	<robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        "Dmitry
 Baryshkov" <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, "David
 Airlie" <airlied@...il.com>,
        Vinod Koul <vkoul@...nel.org>, Simona Vetter
	<simona@...ll.ch>
CC: <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        "Jordan
 Crouse" <jordan@...micpenguin.net>,
        <~postmarketos/upstreaming@...ts.sr.ht>,
        AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
        "Martin
 Botka" <martin.botka@...ainline.org>,
        Jami Kettunen
	<jami.kettunen@...ainline.org>,
        Konrad Dybcio
	<konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH v2 3/3] drm/msm/dpu: Remove arbitrary limit of 1 interface
 in DSC topology



On 2/9/2025 1:42 PM, Marijn Suijten wrote:
> When DSC is enabled the number of interfaces is forced to be 1, and
> documented that it is a "power-optimal" layout to use two DSC encoders
> together with two Layer Mixers.  However, the same layout (two DSC
> hard-slice encoders with two LMs) is also used when the display is
> fed with data over two instead of one interface (common on 4k@...Hz
> smartphone panels with Dual-DSI).  Solve this by simply removing the
> num_intf = 1 assignment as the count is already calculated by computing
> the number of physical encoders within the virtual encoder.
> 
> Fixes: 7e9cc175b159 ("drm/msm/disp/dpu1: Add support for DSC in topology")
> Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>

Reviewed-by: Jessica Zhang <quic_jesszhan@...cinc.com>

> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index b585cd17462345f94bcc2ddd57902cc7c312ae63..b0870318471bd7cceda70fd15ea7bcc8658af604 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -686,20 +686,21 @@ static struct msm_display_topology dpu_encoder_get_topology(
>   
>   	if (dsc) {
>   		/*
> -		 * Use 2 DSC encoders and 2 layer mixers per single interface
> +		 * Use 2 DSC encoders, 2 layer mixers and 1 or 2 interfaces
>   		 * when Display Stream Compression (DSC) is enabled,
>   		 * and when enough DSC blocks are available.
>   		 * This is power-optimal and can drive up to (including) 4k
>   		 * screens.
>   		 */
> -		if (dpu_kms->catalog->dsc_count >= 2) {
> +		WARN(topology.num_intf > 2,
> +		     "DSC topology cannot support more than 2 interfaces\n");
> +		if (intf_count >= 2 || dpu_kms->catalog->dsc_count >= 2) {
>   			topology.num_dsc = 2;
>   			topology.num_lm = 2;
>   		} else {
>   			topology.num_dsc = 1;
>   			topology.num_lm = 1;
>   		}
> -		topology.num_intf = 1;
>   	}
>   
>   	return topology;
> 
> -- 
> 2.48.1
>