linux-kernel - Re: [PATCH v4 15/25] drm/msm/dpu: Add CWB to msm_display

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Message-ID: <ki35rornnos35r3fzg5yyqzxnqua3dyfb6ewq2aefrh4u74vfi@opdnf44ntten>
Date: Fri, 20 Dec 2024 07:03:06 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Jessica Zhang <quic_jesszhan@...cinc.com>
Cc: Rob Clark <robdclark@...il.com>, quic_abhinavk@...cinc.com, 
	Sean Paul <sean@...rly.run>, Marijn Suijten <marijn.suijten@...ainline.org>, 
	David Airlie <airlied@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	Simona Vetter <simona@...ll.ch>, Simona Vetter <simona.vetter@...ll.ch>, 
	quic_ebharadw@...cinc.com, linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org, Rob Clark <robdclark@...omium.org>, 
	Ville Syrjälä <ville.syrjala@...ux.intel.com>
Subject: Re: [PATCH v4 15/25] drm/msm/dpu: Add CWB to msm_display_topology

On Mon, Dec 16, 2024 at 04:43:26PM -0800, Jessica Zhang wrote:
> Add the cwb_enabled flag to msm_display topology and adjust the toplogy
> to account for concurrent writeback

Why?

> 
> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 11 ++++++++++-
>  drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c   | 10 ++++++++--
>  drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h   |  2 ++
>  3 files changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> index b4bfded3d53025853cee112ca598533ece290318..b063c8fe4c0594772d84401fa56c9c21afc0ad18 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> @@ -1198,6 +1198,8 @@ static struct msm_display_topology dpu_crtc_get_topology(
>  		dpu_encoder_update_topology(drm_enc, &topology, crtc_state->state,
>  					    &crtc_state->adjusted_mode);
>  
> +	topology.cwb_enabled = drm_crtc_in_clone_mode(crtc_state);
> +
>  	/*
>  	 * Datapath topology selection
>  	 *
> @@ -1209,9 +1211,16 @@ static struct msm_display_topology dpu_crtc_get_topology(
>  	 * 2 LM, 1 INTF (stream merge to support high resolution interfaces)
>  	 *
>  	 * Add dspps to the reservation requirements if ctm is requested
> +	 *
> +	 * Only hardcode num_lm to 2 for cases where num_intf == 2 and CWB is not
> +	 * enabled. This is because in cases where CWB is enabled, num_intf will
> +	 * count both the WB and real-time phys encoders.
> +	 *
> +	 * For non-DSC CWB usecases, have the num_lm be decided by the
> +	 * (mode->hdisplay > MAX_HDISPLAY_SPLIT) check.
>  	 */
>  
> -	if (topology.num_intf == 2)
> +	if (topology.num_intf == 2 && !topology.cwb_enabled)
>  		topology.num_lm = 2;
>  	else if (topology.num_dsc == 2)
>  		topology.num_lm = 2;
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> index b763ef19f4c60ae8a35df6a6ffb19e8411bc63f8..85adaf256b2c705d2d7df378b6ffc0e578f52bc3 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> @@ -382,8 +382,14 @@ static int _dpu_rm_reserve_ctls(
>  	int i = 0, j, num_ctls;
>  	bool needs_split_display;
>  
> -	/* each hw_intf needs its own hw_ctrl to program its control path */
> -	num_ctls = top->num_intf;
> +	/*
> +	 * For non-CWB mode, each hw_intf needs its own hw_ctl to program its
> +	 * control path. Hardcode num_ctls to 1 if CWB is enabled
> +	 */

Why?

> +	if (top->cwb_enabled)
> +		num_ctls = 1;
> +	else
> +		num_ctls = top->num_intf;
>  
>  	needs_split_display = _dpu_rm_needs_split_display(top);
>  
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
> index b061dfdab52e04ab7d777e912a30173273cb3db7..12db21a2403ec6930894c36a58e898c5d94c2568 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h
> @@ -46,6 +46,7 @@ struct dpu_rm {
>   * @num_dspp:     number of dspp blocks used
>   * @num_dsc:      number of Display Stream Compression (DSC) blocks used
>   * @needs_cdm:    indicates whether cdm block is needed for this display topology
> + * @cwb_enabled:  indicates whether CWB is enabled for this display topology
>   */
>  struct msm_display_topology {
>  	u32 num_lm;
> @@ -53,6 +54,7 @@ struct msm_display_topology {
>  	u32 num_dspp;
>  	u32 num_dsc;
>  	bool needs_cdm;
> +	bool cwb_enabled;
>  };
>  
>  int dpu_rm_init(struct drm_device *dev,
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry