linux-kernel - Re: [PATCH 1/4] drm/msm/disp/dpu1: pin 1 crtc to 1 encoder

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Date:   Wed, 9 Nov 2022 15:19:04 +0300
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 1/4] drm/msm/disp/dpu1: pin 1 crtc to 1 encoder

On 09/11/2022 15:16, 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.
> 
> Signed-off-by: Kalyan Thota <quic_kalyant@...cinc.com>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 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..552a89c 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -798,19 +798,19 @@ static int _dpu_kms_drm_obj_init(struct dpu_kms *dpu_kms)
>   	max_crtc_count = min(max_crtc_count, primary_planes_idx);
>   
>   	/* Create one CRTC per encoder */
> +	encoder = list_first_entry(&(dev)->mode_config.encoder_list,
> +		struct drm_encoder, head);

Please use drm_for_each_encoder() here.

>   	for (i = 0; i < max_crtc_count; i++) {
>   		crtc = dpu_crtc_init(dev, primary_planes[i], cursor_planes[i]);
> -		if (IS_ERR(crtc)) {
> +		if (IS_ERR(crtc) || IS_ERR_OR_NULL(encoder)) {

Why? Not to mention that the OR_NULL part is quite frequently a mistake.

>   			ret = PTR_ERR(crtc);
>   			return ret;
>   		}
>   		priv->crtcs[priv->num_crtcs++] = crtc;
> +		encoder->possible_crtcs = 1 << drm_crtc_index(crtc);
> +		encoder = list_next_entry(encoder, head);
>   	}
>   
> -	/* 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