linux-kernel - Re: [PATCH v4 1/3] drm/msm/disp/dpu1: pin 1 crtc to 1 encoder

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Message-ID: <eeafb291-9da7-da21-8425-c651066f7379@linaro.org>
Date:   Tue, 10 Jan 2023 02:22:26 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Kalyan Thota <quic_kalyant@...cinc.com>,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, robdclark@...omium.org,
        dianders@...omium.org, swboyd@...omium.org,
        quic_vpolimer@...cinc.com, quic_abhinavk@...cinc.com
Subject: Re: [PATCH v4 1/3] drm/msm/disp/dpu1: pin 1 crtc to 1 encoder

On 21/11/2022 11:08, Kalyan Thota wrote:
> Pin each crtc with one encoder. This arrangement will
> disallow crtc switching between encoders and also will
> facilitate to advertise certain features on crtc based
> on encoder type.
> 
> Changes in v1:
> - use drm_for_each_encoder macro while iterating through
>    encoder list (Dmitry)
> 
> Changes in v2:
> - make sure no encoder miss to have a crtc (Dmitry)
> - revisit various factors in deciding the crtc count
>    such as num_mixers, num_sspp (Dmitry)
> 
> Changes in v3:
> - none
> 
> Changes in v4:
> - use max_crtc_count instead of num_encoders in WARN (Dmitry)
> 
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Signed-off-by: Kalyan Thota <quic_kalyant@...cinc.com>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 18 +++++++++++-------
>   1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index 7a5fabc..d967eef 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -795,22 +796,25 @@ static int _dpu_kms_drm_obj_init(struct dpu_kms *dpu_kms)
>   			primary_planes[primary_planes_idx++] = plane;
>   	}
>   
> -	max_crtc_count = min(max_crtc_count, primary_planes_idx);
> +	/*
> +	 * All the platforms should have at least 1 primary plane for a
> +	 * crtc. The below warn should help in setting up the catalog
> +	 */
> +	WARN_ON(max_crtc_count > primary_planes_idx);

This change broke sc7180 support, see 
https://gitlab.freedesktop.org/drm/msm/-/jobs/34395875

I suggest a quick fix of either disabling WB2 or switching one of cursor 
SSPPs to a generic one.

>   
>   	/* Create one CRTC per encoder */
> -	for (i = 0; i < max_crtc_count; i++) {
> +	i = 0;
> +	drm_for_each_encoder(encoder, dev) {
>   		crtc = dpu_crtc_init(dev, primary_planes[i], cursor_planes[i]);
>   		if (IS_ERR(crtc)) {
>   			ret = PTR_ERR(crtc);
>   			return ret;
>   		}
>   		priv->crtcs[priv->num_crtcs++] = crtc;
> +		encoder->possible_crtcs = 1 << drm_crtc_index(crtc);
> +		i++;
>   	}
>   
> -	/* All CRTCs are compatible with all encoders */
> -	drm_for_each_encoder(encoder, dev)
> -		encoder->possible_crtcs = (1 << priv->num_crtcs) - 1;
> -
>   	return 0;
>   }
>   

-- 
With best wishes
Dmitry