linux-kernel - Re: [PATCH 2/3] drm/msm/disp/dpu1: allow dspp selection for all the interfaces

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Message-ID: <24ef467e-24a6-fc8f-3859-95ec0ae109ae@linaro.org>
Date:   Tue, 17 Jan 2023 18:56:25 +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 2/3] drm/msm/disp/dpu1: allow dspp selection for all the
 interfaces

On 17/01/2023 18:21, Kalyan Thota wrote:
> Allow dspps to be populated as a requirement for all the encoder
> types it need not be just DSI. If for any encoder the dspp
> allocation doesn't go through then there can be an option to
> fallback for color features.
> 
> Signed-off-by: Kalyan Thota <quic_kalyant@...cinc.com>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 18 +++++++++---------
>   1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index 9c6817b..e39b345 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -545,7 +545,8 @@ bool dpu_encoder_use_dsc_merge(struct drm_encoder *drm_enc)
>   static struct msm_display_topology dpu_encoder_get_topology(
>   			struct dpu_encoder_virt *dpu_enc,
>   			struct dpu_kms *dpu_kms,
> -			struct drm_display_mode *mode)
> +			struct drm_display_mode *mode,
> +			struct drm_crtc_state *crtc_state)

Is this new argument used at all?

>   {
>   	struct msm_display_topology topology = {0};
>   	int i, intf_count = 0;
> @@ -563,8 +564,9 @@ static struct msm_display_topology dpu_encoder_get_topology(
>   	 * 1 LM, 1 INTF
>   	 * 2 LM, 1 INTF (stream merge to support high resolution interfaces)
>   	 *
> -	 * Adding color blocks only to primary interface if available in
> -	 * sufficient number
> +	 * dspp blocks are made optional. If RM manager cannot allocate
> +	 * dspp blocks, then reservations will still go through with non dspp LM's
> +	 * so as to allow color management support via composer fallbacks
>   	 */

No, this is not the way to go.

First, RM should prefer non-DSPP-enabled LMs if DSPP blocks are not 
required.  Right now your patch makes it possible to allocate LMs, that 
have DSPP attached, for non-CTM-enabled encoder and later fail 
allocation of DSPP for the CRTC which has CTM blob attached.

Second, the decision on using DSPPs should come from 
dpu_crtc_atomic_check(). Pass 'bool need_dspp' to this function from 
dpu_atomic_check(). Fail if the need_dspp constraint can't be fulfilled.


>   	if (intf_count == 2)
>   		topology.num_lm = 2;
> @@ -573,11 +575,9 @@ static struct msm_display_topology dpu_encoder_get_topology(
>   	else
>   		topology.num_lm = (mode->hdisplay > MAX_HDISPLAY_SPLIT) ? 2 : 1;
>   
> -	if (dpu_enc->disp_info.intf_type == DRM_MODE_ENCODER_DSI) {
> -		if (dpu_kms->catalog->dspp &&
> -			(dpu_kms->catalog->dspp_count >= topology.num_lm))
> -			topology.num_dspp = topology.num_lm;
> -	}
> +	if (dpu_kms->catalog->dspp &&
> +	    (dpu_kms->catalog->dspp_count >= topology.num_lm))
> +		topology.num_dspp = topology.num_lm;
>   
>   	topology.num_enc = 0;
>   	topology.num_intf = intf_count;
> @@ -643,7 +643,7 @@ static int dpu_encoder_virt_atomic_check(
>   		}
>   	}
>   
> -	topology = dpu_encoder_get_topology(dpu_enc, dpu_kms, adj_mode);
> +	topology = dpu_encoder_get_topology(dpu_enc, dpu_kms, adj_mode, crtc_state);
>   
>   	/* Reserve dynamic resources now. */
>   	if (!ret) {

-- 
With best wishes
Dmitry