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

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Jun 27, 2018 at 11:03:31AM +0200, Daniel Vetter wrote:
> 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.

Yeah. This one is obviously crap. Originally I had it after the
for_each_encoder_ids() thing so didn't need any checks, but then
thought I should move it before just in case people don't like
that particular macro. And apparently forgot to think when doing
that.

> 
> 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

-- 
Ville Syrjälä
Intel
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