Re: [PATCH 1/8] drm/fb-helper: Eliminate the .best_encoder() usage

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Jun 26, 2018 at 08:47:07PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Instead of using the .best_encoder() hook to figure out whether a given
> connector+crtc combo will work, let's instead do what userspace does and
> just iterate over all the encoders for the connector, and then check
> each crtc against each encoder's possible_crtcs bitmask.
> 
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_fb_helper.c | 36 +++++++++++++++++++-----------------
>  1 file changed, 19 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index cab14f253384..61c39cd75a27 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -2323,6 +2323,23 @@ static bool drm_target_preferred(struct drm_fb_helper *fb_helper,
>  	return true;
>  }
>  
> +static bool connector_crtc_ok(struct drm_connector *connector,
> +			      struct drm_crtc *crtc)
> +{
> +	int i;
> +
> +	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++) {
> +		struct drm_encoder *encoder =
> +			drm_encoder_find(connector->dev, NULL,
> +					 connector->encoder_ids[i]);
> +

Shouldn't we also check for encoder != NULL here? Just for the case where
a connector does not work on the given crtc, where we do expect to
actually run off the end of the valid entries in the array.

With that fixed:

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> +		if (encoder->possible_crtcs & drm_crtc_mask(crtc))
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
>  static int drm_pick_crtcs(struct drm_fb_helper *fb_helper,
>  			  struct drm_fb_helper_crtc **best_crtcs,
>  			  struct drm_display_mode **modes,
> @@ -2331,7 +2348,6 @@ static int drm_pick_crtcs(struct drm_fb_helper *fb_helper,
>  	int c, o;
>  	struct drm_connector *connector;
>  	const struct drm_connector_helper_funcs *connector_funcs;
> -	struct drm_encoder *encoder;
>  	int my_score, best_score, score;
>  	struct drm_fb_helper_crtc **crtcs, *crtc;
>  	struct drm_fb_helper_connector *fb_helper_conn;
> @@ -2362,20 +2378,6 @@ static int drm_pick_crtcs(struct drm_fb_helper *fb_helper,
>  
>  	connector_funcs = connector->helper_private;
>  
> -	/*
> -	 * If the DRM device implements atomic hooks and ->best_encoder() is
> -	 * NULL we fallback to the default drm_atomic_helper_best_encoder()
> -	 * helper.
> -	 */
> -	if (drm_drv_uses_atomic_modeset(fb_helper->dev) &&
> -	    !connector_funcs->best_encoder)
> -		encoder = drm_atomic_helper_best_encoder(connector);
> -	else
> -		encoder = connector_funcs->best_encoder(connector);
> -
> -	if (!encoder)
> -		goto out;
> -
>  	/*
>  	 * select a crtc for this connector and then attempt to configure
>  	 * remaining connectors
> @@ -2383,7 +2385,7 @@ static int drm_pick_crtcs(struct drm_fb_helper *fb_helper,
>  	for (c = 0; c < fb_helper->crtc_count; c++) {
>  		crtc = &fb_helper->crtc_info[c];
>  
> -		if ((encoder->possible_crtcs & (1 << c)) == 0)
> +		if (!connector_crtc_ok(connector, crtc->mode_set.crtc))
>  			continue;
>  
>  		for (o = 0; o < n; o++)
> @@ -2410,7 +2412,7 @@ static int drm_pick_crtcs(struct drm_fb_helper *fb_helper,
>  			       sizeof(struct drm_fb_helper_crtc *));
>  		}
>  	}
> -out:
> +
>  	kfree(crtcs);
>  	return best_score;
>  }
> -- 
> 2.16.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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