Re: [PATCH v10 1/2] drm: Add connector property to limit max bpc

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Oct 03, 2018 at 03:24:40PM -0700, Radhakrishna Sripada wrote:
> On Mon, Oct 01, 2018 at 09:23:38AM +0200, Daniel Vetter wrote:
> > On Mon, Sep 24, 2018 at 02:08:14PM -0700, Radhakrishna Sripada wrote:
> > > At times 12bpc HDMI cannot be driven due to faulty cables, dongles
> > > level shifters etc. To workaround them we may need to drive the output
> > > at a lower bpc. Currently the user space does not have a way to limit
> > > the bpc. The default bpc to be programmed is decided by the driver and
> > > is run against connector limitations.
> > > 
> > > Creating a new connector property "max bpc" in order to limit the bpc.
> > > xrandr can make use of this connector property to make sure that bpc does
> > > not exceed the configured value. This property can be used by userspace to
> > > set the bpc.
> > > 
> > > V2: Initialize max_bpc to satisfy kms_properties
> > > V3: Move the property to drm_connector
> > > V4: Split drm and i915 components(Ville)
> > > V5: Make the property per connector(Ville)
> > > V6: Compare the requested bpc to connector bpc(Daniel)
> > >     Move the attach_property function to core(Ville)
> > > V7: Fix checkpatch warnings
> > > V8: Simplify the connector check code(Ville)
> > > V9: Const display_info(Ville)
> > > V10: Fix CI issues.
> > > 
> > > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > > Cc: Kishore Kadiyala <kishore.kadiyala@intel.com>
> > > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > > Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> > > Cc: Sunpeng Li <sunpeng.li@amd.com>
> > > Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
> > 
> > Skimming this, I think it looks good now at a high-level.
> > 
> > What's missing is now kernel-doc for these new prorties, needs to be added
> > here:
> > 
> > https://dri.freedesktop.org/docs/drm/gpu/drm-kms.html#standard-connector-properties
> > 
> > With that I'm happy with the high-level design:
> > 
> > Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> > 
> > No full review since I didn't look at the igt side for this. Userspace I
> > think is ok, since it's just another connector prop.
> kms_properties would test this newly added property as part of the connector properties.
> Do you suggest me to add a new subtest to try checking the different values for the 
> newly added property?

kms_properties most definitely doesn't do any kind of functional testing
here. Which means it's not validated in an automatic way.

So yes, we most definitely want a real testcase here. Coming up with a
proper validation strategy here is going to be somewhat challenging
though.

Thanks, Daniel

> 
> --Radhakrishna Sripada
> > -Daniel
> > 
> > > ---
> > >  drivers/gpu/drm/drm_atomic.c        |  5 +++++
> > >  drivers/gpu/drm/drm_atomic_helper.c |  4 ++++
> > >  drivers/gpu/drm/drm_atomic_uapi.c   |  4 ++++
> > >  drivers/gpu/drm/drm_connector.c     | 33 +++++++++++++++++++++++++++++++++
> > >  include/drm/drm_connector.h         | 20 ++++++++++++++++++++
> > >  5 files changed, 66 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > > index 2870ae205237..f328bcca84a8 100644
> > > --- a/drivers/gpu/drm/drm_atomic.c
> > > +++ b/drivers/gpu/drm/drm_atomic.c
> > > @@ -390,6 +390,7 @@ static int drm_atomic_connector_check(struct drm_connector *connector,
> > >  {
> > >  	struct drm_crtc_state *crtc_state;
> > >  	struct drm_writeback_job *writeback_job = state->writeback_job;
> > > +	const struct drm_display_info *info = &connector->display_info;
> > >  
> > >  	if ((connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK) || !writeback_job)
> > >  		return 0;
> > > @@ -417,6 +418,10 @@ static int drm_atomic_connector_check(struct drm_connector *connector,
> > >  		return -EINVAL;
> > >  	}
> > >  
> > > +	state->max_bpc = info->bpc ? info->bpc : 8;
> > > +	if (connector->max_bpc_property)
> > > +		state->max_bpc = min(state->max_bpc, state->max_requested_bpc);
> > > +
> > >  	return 0;
> > >  }
> > >  
> > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> > > index e49b22381048..75aeca35f6d9 100644
> > > --- a/drivers/gpu/drm/drm_atomic_helper.c
> > > +++ b/drivers/gpu/drm/drm_atomic_helper.c
> > > @@ -639,6 +639,10 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
> > >  			if (old_connector_state->link_status !=
> > >  			    new_connector_state->link_status)
> > >  				new_crtc_state->connectors_changed = true;
> > > +
> > > +			if (old_connector_state->max_requested_bpc !=
> > > +			    new_connector_state->max_requested_bpc)
> > > +				new_crtc_state->connectors_changed = true;
> > >  		}
> > >  
> > >  		if (funcs->atomic_check)
> > > diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> > > index d5b7f315098c..86ac33922b09 100644
> > > --- a/drivers/gpu/drm/drm_atomic_uapi.c
> > > +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> > > @@ -740,6 +740,8 @@ static int drm_atomic_connector_set_property(struct drm_connector *connector,
> > >  
> > >  		return set_out_fence_for_connector(state->state, connector,
> > >  						   fence_ptr);
> > > +	} else if (property == connector->max_bpc_property) {
> > > +		state->max_requested_bpc = val;
> > >  	} else if (connector->funcs->atomic_set_property) {
> > >  		return connector->funcs->atomic_set_property(connector,
> > >  				state, property, val);
> > > @@ -804,6 +806,8 @@ drm_atomic_connector_get_property(struct drm_connector *connector,
> > >  		*val = 0;
> > >  	} else if (property == config->writeback_out_fence_ptr_property) {
> > >  		*val = 0;
> > > +	} else if (property == connector->max_bpc_property) {
> > > +		*val = state->max_requested_bpc;
> > >  	} else if (connector->funcs->atomic_get_property) {
> > >  		return connector->funcs->atomic_get_property(connector,
> > >  				state, property, val);
> > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > > index 1e40e5decbe9..65e22c1b37a5 100644
> > > --- a/drivers/gpu/drm/drm_connector.c
> > > +++ b/drivers/gpu/drm/drm_connector.c
> > > @@ -1583,6 +1583,39 @@ void drm_connector_set_link_status_property(struct drm_connector *connector,
> > >  EXPORT_SYMBOL(drm_connector_set_link_status_property);
> > >  
> > >  /**
> > > + * drm_connector_attach_max_bpc_property - attach "max bpc" property
> > > + * @connector: connector to attach max bpc property on.
> > > + * @min: The minimum bit depth supported by the connector.
> > > + * @max: The maximum bit depth supported by the connector.
> > > + *
> > > + * This is used to add support for limiting the bit depth on a connector.
> > > + *
> > > + * Returns:
> > > + * Zero on success, negative errno on failure.
> > > + */
> > > +int drm_connector_attach_max_bpc_property(struct drm_connector *connector,
> > > +					  int min, int max)
> > > +{
> > > +	struct drm_device *dev = connector->dev;
> > > +	struct drm_property *prop;
> > > +
> > > +	prop = connector->max_bpc_property;
> > > +	if (!prop) {
> > > +		prop = drm_property_create_range(dev, 0, "max bpc", min, max);
> > > +		if (!prop)
> > > +			return -ENOMEM;
> > > +
> > > +		connector->max_bpc_property = prop;
> > > +	}
> > > +
> > > +	drm_object_attach_property(&connector->base, prop, max);
> > > +	connector->state->max_requested_bpc = max;
> > > +
> > > +	return 0;
> > > +}
> > > +EXPORT_SYMBOL(drm_connector_attach_max_bpc_property);
> > > +
> > > +/**
> > >   * drm_connector_init_panel_orientation_property -
> > >   *	initialize the connecters panel_orientation property
> > >   * @connector: connector for which to init the panel-orientation property.
> > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> > > index 91a877fa00cb..bfc3e698cda6 100644
> > > --- a/include/drm/drm_connector.h
> > > +++ b/include/drm/drm_connector.h
> > > @@ -461,6 +461,18 @@ struct drm_connector_state {
> > >  	 * drm_writeback_signal_completion()
> > >  	 */
> > >  	struct drm_writeback_job *writeback_job;
> > > +
> > > +	/**
> > > +	 * @max_requested_bpc: Connector property to limit the maximum bit
> > > +	 * depth of the pixels.
> > > +	 */
> > > +	u8 max_requested_bpc;
> > > +
> > > +	/**
> > > +	 * @max_bpc: Connector max_bpc based on the requested max_bpc property
> > > +	 * and the connector bpc limitations obtained from edid.
> > > +	 */
> > > +	u8 max_bpc;
> > >  };
> > >  
> > >  /**
> > > @@ -924,6 +936,12 @@ struct drm_connector {
> > >  	 */
> > >  	struct drm_property_blob *path_blob_ptr;
> > >  
> > > +	/**
> > > +	 * @max_bpc_property: Default connector property for the max bpc to be
> > > +	 * driven out of the connector.
> > > +	 */
> > > +	struct drm_property *max_bpc_property;
> > > +
> > >  #define DRM_CONNECTOR_POLL_HPD (1 << 0)
> > >  #define DRM_CONNECTOR_POLL_CONNECT (1 << 1)
> > >  #define DRM_CONNECTOR_POLL_DISCONNECT (1 << 2)
> > > @@ -1201,6 +1219,8 @@ void drm_connector_set_link_status_property(struct drm_connector *connector,
> > >  					    uint64_t link_status);
> > >  int drm_connector_init_panel_orientation_property(
> > >  	struct drm_connector *connector, int width, int height);
> > > +int drm_connector_attach_max_bpc_property(struct drm_connector *connector,
> > > +					  int min, int max);
> > >  
> > >  /**
> > >   * struct drm_tile_group - Tile group metadata
> > > -- 
> > > 2.9.3
> > > 
> > 
> > -- 
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > http://blog.ffwll.ch

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