linux-kernel - Re: [PATCH v2 13/22] drm/msm/dpu: Add CWB to msm_display

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Message-ID: <so3sfdgwfc5zwm56w7b2zhru4nmkmwvppxtvbri5a44d2cg3fb@xdcfai3sbwwt>
Date: Wed, 25 Sep 2024 02:22:34 +0300
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>, Daniel Vetter <daniel@...ll.ch>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, 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 v2 13/22] drm/msm/dpu: Add CWB to msm_display_topology

On Tue, Sep 24, 2024 at 03:59:29PM GMT, Jessica Zhang wrote:
> Add the cwb_enabled flag to msm_display topology and adjust the toplogy
> to account for concurrent writeback
> 
> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c |  6 ++++--
>  drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c   | 10 ++++++++--
>  drivers/gpu/drm/msm/msm_drv.h            |  2 ++
>  3 files changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> index d53e986eee54..a7850bf844db 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> @@ -1176,6 +1176,8 @@ 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
>  	 *
> @@ -1189,9 +1191,9 @@ static struct msm_display_topology dpu_crtc_get_topology(
>  	 * Add dspps to the reservation requirements if ctm is requested
>  	 */
>  
> -	if (topology.num_intf == 2)
> +	if (topology.num_intf == 2 && !topology.cwb_enabled)
>  		topology.num_lm = 2;
> -	else if (topology.num_dsc == 2)
> +	else if (topology.num_dsc == 2 && !topology.cwb_enabled)

Is it a temporal restriction or is it a hardware limitation? Can we use
two LMs with a single WB?

>  		topology.num_lm = 2;
>  	else if (dpu_kms->catalog->caps->has_3d_merge)
>  		topology.num_lm = (mode->hdisplay > MAX_HDISPLAY_SPLIT) ? 2 : 1;
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> index 96c80cf9f6ad..04df3056d75a 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> @@ -371,8 +371,14 @@ 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
> +	 */
> +	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/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
> index 0d3adf398bc1..8a2a3705f117 100644
> --- a/drivers/gpu/drm/msm/msm_drv.h
> +++ b/drivers/gpu/drm/msm/msm_drv.h
> @@ -1,5 +1,6 @@
>  /* SPDX-License-Identifier: GPL-2.0-only */
>  /*
> + * Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
>   * Copyright (c) 2016-2018, The Linux Foundation. All rights reserved.
>   * Copyright (C) 2013 Red Hat
>   * Author: Rob Clark <robdclark@...il.com>
> @@ -88,6 +89,7 @@ struct msm_display_topology {
>  	u32 num_dspp;
>  	u32 num_dsc;
>  	bool needs_cdm;
> +	bool cwb_enabled;
>  };
>  
>  /* Commit/Event thread specific structure */
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry