linux-kernel - Re: [PATCH v6 06/14] drm/msm/dpu: Fail atomic_check if multiple outputs request CDM block

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Message-ID: <wfhusui6qv6c4knns7ux6z7qnehzokoa6bj2ufanlnlkqpnvkj@qykctcbwizdn>
Date: Sat, 15 Feb 2025 17:26:15 +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 v6 06/14] drm/msm/dpu: Fail atomic_check if multiple
 outputs request CDM block

On Fri, Feb 14, 2025 at 04:14:29PM -0800, Jessica Zhang wrote:
> Currently, our hardware only supports a single output using CDM block at
> most. Because of this, we cannot support cases where both writeback and DP
> output request CDM simultaneously
> 
> To avoid this happening when CWB is enabled, change
> msm_display_topoloy.needs_cdm into a num_cdm counter to track how many
> outputs are requesting CDM block. Return EINVAL if multiple outputs are
> trying to reserve CDM.
> 
> Signed-off-by: Jessica Zhang <quic_jesszhan@...cinc.com>
> ---
> Changes in v6:
> - cdm_requested -> num_cdm
> 
> Changes in v5:
> - Changed check to fail only if multiple outputs are requesting CDM
>   simultaneously
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c |  4 ++--
>  drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c      | 12 +++++++++---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_rm.h      |  5 +++--
>  3 files changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index ad969a5b9434..0e4f27da9534 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -692,10 +692,10 @@ void dpu_encoder_update_topology(struct drm_encoder *drm_enc,
>  		fb = conn_state->writeback_job->fb;
>  
>  		if (fb && MSM_FORMAT_IS_YUV(msm_framebuffer_format(fb)))
> -			topology->needs_cdm = true;
> +			topology->num_cdm++;
>  	} else if (disp_info->intf_type == INTF_DP) {
>  		if (msm_dp_is_yuv_420_enabled(priv->dp[disp_info->h_tile_instance[0]], adj_mode))
> -			topology->needs_cdm = true;
> +			topology->num_cdm++;
>  	}
>  }
>  
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> index 0fbb92021b18..4da2e47265d4 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> @@ -585,7 +585,8 @@ static int _dpu_rm_reserve_dsc(struct dpu_rm *rm,
>  
>  static int _dpu_rm_reserve_cdm(struct dpu_rm *rm,
>  			       struct dpu_global_state *global_state,
> -			       uint32_t crtc_id)
> +			       uint32_t crtc_id,
> +			       int num_cdm)
>  {
>  	/* try allocating only one CDM block */
>  	if (!rm->cdm_blk) {
> @@ -593,6 +594,11 @@ static int _dpu_rm_reserve_cdm(struct dpu_rm *rm,
>  		return -EIO;
>  	}
>  
> +	if (num_cdm > 1) {
> +		DPU_ERROR("More than 1 INTF requesting CDM\n");

I think we should downgrade those to DPU_DEBUG or something like that,
but that can go separately, or when picking the patch up.

Nevertheless:

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>


> +		return -EINVAL;
> +	}
> +
>  	if (global_state->cdm_to_crtc_id) {
>  		DPU_ERROR("CDM_0 is already allocated\n");
>  		return -EIO;
-- 
With best wishes
Dmitry