linux-kernel - Re: [PATCH v3 09/13] drm/msm/disp/dpu1: Add support for DSC in topology

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Date:   Wed, 24 Nov 2021 18:59:47 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Vinod Koul <vkoul@...nel.org>, Rob Clark <robdclark@...il.com>
Cc:     linux-arm-msm@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jonathan Marek <jonathan@...ek.ca>,
        Abhinav Kumar <abhinavk@...eaurora.org>,
        Jeffrey Hugo <jeffrey.l.hugo@...il.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org
Subject: Re: [PATCH v3 09/13] drm/msm/disp/dpu1: Add support for DSC in
 topology

On 16/11/2021 09:22, Vinod Koul wrote:
> For DSC to work we typically need a 2,2,1 configuration. This should
> suffice for resolutions up to 4k. For more resolutions like 8k this won't
> work.
> 
> Also, it is better to use 2 LMs and DSC instances as half width results
> in lesser power consumption as compared to single LM, DSC at full width.
> 
> The panel has been tested only with 2,2,1 configuration, so for
> now we blindly create 2,2,1 topology when DSC is enabled
> 
> Co-developed-by: Abhinav Kumar <abhinavk@...eaurora.org>
> Signed-off-by: Abhinav Kumar <abhinavk@...eaurora.org>
> Signed-off-by: Vinod Koul <vkoul@...nel.org>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 18 ++++++++++++++++++
>   drivers/gpu/drm/msm/msm_drv.h               |  2 ++
>   2 files changed, 20 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index f2ff8a504918..12f58de88ac7 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -533,6 +533,8 @@ static struct msm_display_topology dpu_encoder_get_topology(
>   			struct drm_display_mode *mode)
>   {
>   	struct msm_display_topology topology = {0};
> +	struct drm_encoder *drm_enc;
> +	struct msm_drm_private *priv;
>   	int i, intf_count = 0;
>   
>   	for (i = 0; i < MAX_PHYS_ENCODERS_PER_VIRTUAL; i++)
> @@ -567,8 +569,24 @@ static struct msm_display_topology dpu_encoder_get_topology(
>   	topology.num_enc = 0;
>   	topology.num_intf = intf_count;
>   
> +	drm_enc = &dpu_enc->base;
> +	priv = drm_enc->dev->dev_private;
> +	if (priv && priv->dsc) {
> +		/* In case of Display Stream Compression DSC, we would use
> +		 * 2 encoders, 2 line mixers and 1 interface
> +		 * this is power optimal and can drive up to (including) 4k
> +		 * screens
> +		 */
> +		topology.num_enc = 2;
> +		topology.num_dsc = 2;
> +		topology.num_intf = 1;
> +		topology.num_lm = 2;
> +		priv->dsc->dsc_mask = BIT(0) | BIT(1);

dsc_mask is still hardcoded here. We should use DSC indices returned 
from RM.

> +	}
> +
>   	return topology;
>   }
> +
>   static int dpu_encoder_virt_atomic_check(
>   		struct drm_encoder *drm_enc,
>   		struct drm_crtc_state *crtc_state,
> diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index c4a588ad226e..d6b25d77700e 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -103,12 +103,14 @@ enum msm_event_wait {
>    * @num_enc:      number of compression encoder blocks used
>    * @num_intf:     number of interfaces the panel is mounted on
>    * @num_dspp:     number of dspp blocks used
> + * @num_dsc:      number of Display Stream Compression (DSC) blocks used
>    */
>   struct msm_display_topology {
>   	u32 num_lm;
>   	u32 num_enc;
>   	u32 num_intf;
>   	u32 num_dspp;
> +	u32 num_dsc;
>   };
>   
>   /**
> 


-- 
With best wishes
Dmitry