Re: [PATCH v3 4/6] drm: Use new mode_valid() helpers in connector probe helper

[Daniel Vetter]

On Mon, May 15, 2017 at 10:39:35AM +0200, Andrzej Hajda wrote:
> On 11.05.2017 11:06, Jose Abreu wrote:
> > This changes the connector probe helper function to use the new
> > encoder->mode_valid(), bridge->mode_valid() and crtc->mode_valid()
> > helper callbacks to validate the modes.
> >
> > The new callbacks are optional so the behaviour remains the same
> > if they are not implemented. If they are, then the code loops
> > through all the connector's encodersXbridgesXcrtcs and calls the
> > callback.
> >
> > If at least a valid encoderXbridgeXcrtc combination is found which
> > accepts the mode then the function returns MODE_OK.
> >
> > Signed-off-by: Jose Abreu <joabreu@xxxxxxxxxxxx>
> > Cc: Carlos Palminha <palminha@xxxxxxxxxxxx>
> > Cc: Alexey Brodkin <abrodkin@xxxxxxxxxxxx>
> > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > Cc: Dave Airlie <airlied@xxxxxxxx>
> > Cc: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
> > Cc: Archit Taneja <architt@xxxxxxxxxxxxxx>
> > ---
> >
> > Changes v2->v3:
> > 	- Call also bridge->mode_valid (Daniel)
> > Changes v1->v2:
> > 	- Use new helpers suggested by Ville
> > 	- Change documentation (Daniel)
> >
> >  drivers/gpu/drm/drm_probe_helper.c | 65 ++++++++++++++++++++++++++++++++++++--
> >  1 file changed, 62 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> > index f01abdc..84d660e 100644
> > --- a/drivers/gpu/drm/drm_probe_helper.c
> > +++ b/drivers/gpu/drm/drm_probe_helper.c
> > @@ -83,6 +83,61 @@
> >  	return MODE_OK;
> >  }
> >  
> > +static enum drm_mode_status
> > +drm_mode_validate_connector(struct drm_connector *connector,
> > +			    struct drm_display_mode *mode)
> > +{
> > +	struct drm_device *dev = connector->dev;
> > +	uint32_t *ids = connector->encoder_ids;
> > +	enum drm_mode_status ret = MODE_OK;
> > +	unsigned int i;
> > +
> > +	/* Step 1: Validate against connector */
> > +	ret = drm_connector_mode_valid(connector, mode);
> > +	if (ret != MODE_OK)
> > +		return ret;
> > +
> > +	/* Step 2: Validate against encoders and crtcs */
> > +	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++) {
> > +		struct drm_encoder *encoder = drm_encoder_find(dev, ids[i]);
> > +		struct drm_crtc *crtc;
> > +
> > +		if (!encoder)
> > +			continue;
> > +
> > +		ret = drm_encoder_mode_valid(encoder, mode);
> > +		if (ret != MODE_OK) {
> > +			/* No point in continuing for crtc check as this encoder
> > +			 * will not accept the mode anyway. If all encoders
> > +			 * reject the mode then, at exit, ret will not be
> > +			 * MODE_OK. */
> > +			continue;
> > +		}
> > +
> > +		ret = drm_bridge_mode_valid(encoder->bridge, mode);
> > +		if (ret != MODE_OK) {
> > +			/* There is also no point in continuing for crtc check
> > +			 * here. */
> > +			continue;
> > +		}
> 
> Maybe it is a bikeshedding, but wouldn't be better to call
> drm_bridge_mode_valid from drm_encoder_mode_valid, in general call all
> bridge related stuff from corresponding encoder stuff?
> This is more question about role of encoder->bridge, should it be
> treated as encoder's extension, or as 1st class citizen in drm?
> 
> Another concern is about order of calls, it is from sink to source, to
> keep it consistent bridge should be called before encoder, am I right?

For the atomic_check stuff (where we do change the passed-in mode) this
would be correct, and calling order and layering would matter. But this
just validates the mode in turn with everything, not taking any
cross-component constraint or other configuration-dependent constraints
into account. Hence it doesn't matter in which order we call stuff.

Note that the passed-in mode is const, so you can't escape. And v3 of
patch 1 now has added wording that you're not allowed to look at anything
else dynamie either.

Does that address your concern?
-Daniel

> Beside this:
> Reviewed-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
> 
>  --
> Regards
> Andrzej
> 
> > +
> > +		drm_for_each_crtc(crtc, dev) {
> > +			if (!drm_encoder_crtc_ok(encoder, crtc))
> > +				continue;
> > +
> > +			ret = drm_crtc_mode_valid(crtc, mode);
> > +			if (ret == MODE_OK) {
> > +				/* If we get to this point there is at least
> > +				 * one combination of encoder+crtc that works
> > +				 * for this mode. Lets return now. */
> > +				return ret;
> > +			}
> > +		}
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> >  static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
> >  {
> >  	struct drm_cmdline_mode *cmdline_mode;
> > @@ -322,7 +377,11 @@ void drm_kms_helper_poll_enable(struct drm_device *dev)
> >   *    - drm_mode_validate_flag() checks the modes against basic connector
> >   *      capabilities (interlace_allowed,doublescan_allowed,stereo_allowed)
> >   *    - the optional &drm_connector_helper_funcs.mode_valid helper can perform
> > - *      driver and/or hardware specific checks
> > + *      driver and/or sink specific checks
> > + *    - the optional &drm_crtc_helper_funcs.mode_valid,
> > + *      &drm_bridge_funcs.mode_valid and &drm_encoder_helper_funcs.mode_valid
> > + *      helpers can perform driver and/or source specific checks which are also
> > + *      enforced by the modeset/atomic helpers
> >   *
> >   * 5. Any mode whose status is not OK is pruned from the connector's modes list,
> >   *    accompanied by a debug message indicating the reason for the mode's
> > @@ -466,8 +525,8 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
> >  		if (mode->status == MODE_OK)
> >  			mode->status = drm_mode_validate_flag(mode, mode_flags);
> >  
> > -		if (mode->status == MODE_OK && connector_funcs->mode_valid)
> > -			mode->status = connector_funcs->mode_valid(connector,
> > +		if (mode->status == MODE_OK)
> > +			mode->status = drm_mode_validate_connector(connector,
> >  								   mode);
> >  	}
> >  
> 
> 

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