Re: [PATCH] drm: rcar-du: Support panels connected directly to the DPAD outputs

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Jacopo,

On Wed, Mar 06, 2019 at 11:03:32AM +0100, Jacopo Mondi wrote:
> On Sat, Mar 02, 2019 at 06:17:25PM +0200, Laurent Pinchart wrote:
> > The R-Car DU driver assumes that a bridge is always connected to the DU
> > output. This is valid for the LVDS and HDMI outputs, but the DPAD
> > outputs can be connected directly to a panel, in which case no bridge is
> > available.
> >
> > To support this use case, detect whether the entities connected to the
> > DU DPAD outputs are encoders or panels based on the number of ports of
> > their DT node, and retrieve the corresponding type of DRM objects. For
> > panels, additionally create panel bridge instances.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> > ---
> >  drivers/gpu/drm/rcar-du/rcar_du_encoder.c | 54 ++++++++++++++++++++---
> >  1 file changed, 48 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_du_encoder.c b/drivers/gpu/drm/rcar-du/rcar_du_encoder.c
> > index 8ee4e762f4e5..595ecfa1ff0e 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_du_encoder.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_du_encoder.c
> > @@ -28,13 +28,33 @@ static const struct drm_encoder_funcs encoder_funcs = {
> >  	.destroy = drm_encoder_cleanup,
> >  };
> >
> > +static unsigned int rcar_du_encoder_count_ports(struct device_node *node)
> > +{
> > +	struct device_node *ports;
> > +	struct device_node *port;
> > +	unsigned int num_ports = 0;
> > +
> > +	ports = of_get_child_by_name(node, "ports");
> > +	if (!ports)
> > +		ports = of_node_get(node);
> > +
> > +	for_each_child_of_node(ports, port) {
> > +		if (of_node_name_eq(port, "port"))
> > +			num_ports++;
> > +	}
> > +
> > +	of_node_put(node);
> > +
> > +	return num_ports;
> > +}
> > +
> >  int rcar_du_encoder_init(struct rcar_du_device *rcdu,
> >  			 enum rcar_du_output output,
> >  			 struct device_node *enc_node)
> >  {
> 
> You received a Tested-by, so I might surely be mistaken, but the
> caller of this function skips all remote nodes with a single port,
> doesn't it?
> https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/rcar-du/rcar_du_kms.c#L308
> 
> I don't have any DTS with a panel connected to the DPAD output so, as
> a test, I removed all endpoints except endpoint@0 from the 'hdmi0' device
> node, and the 'rcar_du_encoder_init()' function never gets called and DU
> probing fails with:
> rcar-du feb00000.display: no encoder found for endpoint /soc/display@feb00000/ports/port@1/endpoint, skipping
> 
> What am I missing?

You're missing drm-next :-)

https://cgit.freedesktop.org/drm/drm/tree/drivers/gpu/drm/rcar-du/rcar_du_kms.c#n331

> >  	struct rcar_du_encoder *renc;
> >  	struct drm_encoder *encoder;
> > -	struct drm_bridge *bridge = NULL;
> > +	struct drm_bridge *bridge;
> >  	int ret;
> >
> >  	renc = devm_kzalloc(rcdu->dev, sizeof(*renc), GFP_KERNEL);
> > @@ -48,11 +68,33 @@ int rcar_du_encoder_init(struct rcar_du_device *rcdu,
> >  	dev_dbg(rcdu->dev, "initializing encoder %pOF for output %u\n",
> >  		enc_node, output);
> >
> > -	/* Locate the DRM bridge from the encoder DT node. */
> > -	bridge = of_drm_find_bridge(enc_node);
> > -	if (!bridge) {
> > -		ret = -EPROBE_DEFER;
> > -		goto done;
> > +	/*
> > +	 * Locate the DRM bridge from the DT node. For the DPAD outputs, if the
> > +	 * DT node has a single port, consider it describes a panel and create a
> > +	 * panel bridge.
> > +	 */
> > +	if ((output == RCAR_DU_OUTPUT_DPAD0 ||
> > +	     output == RCAR_DU_OUTPUT_DPAD1) &&
> > +	    rcar_du_encoder_count_ports(enc_node) == 1) {
> 
> Could this be cached?

How so ? This function is run once per enc_node, so the cache wouldn't
be used again, would it ?

> > +		struct drm_panel *panel = of_drm_find_panel(enc_node);
> > +
> > +		if (IS_ERR(panel)) {
> > +			ret = PTR_ERR(panel);
> > +			goto done;
> > +		}
> > +
> > +		bridge = devm_drm_panel_bridge_add(rcdu->dev, panel,
> > +						   DRM_MODE_CONNECTOR_DPI);
> > +		if (IS_ERR(bridge)) {
> > +			ret = PTR_ERR(bridge);
> > +			goto done;
> > +		}
> > +	} else {
> > +		bridge = of_drm_find_bridge(enc_node);
> > +		if (!bridge) {
> > +			ret = -EPROBE_DEFER;
> > +			goto done;
> > +		}
> >  	}
> >
> >  	ret = drm_encoder_init(rcdu->ddev, encoder, &encoder_funcs,

-- 
Regards,

Laurent Pinchart