Re: [PATCH v6 2/6] drm: sun4i: dsi: Add component only once DSI device attached

On Fri, Dec 10, 2021 at 04:47:07PM +0530, Jagan Teki wrote:

Having component_add for running all drm bind callbacks returns error or unbound due to chain of DSI devices connected across bridge topology on a display pipeline.

I'm not sure what that means?

In a typical bridge oriented display pipeline where the host is connected to the bridge converter and that indeed connected to a panel.

DRM => SUN6I DSI Host => Chipone ICN6211 => BananaPi Panel

The bridge converter is looking for a panel to probe first and then attach the host. The host attach is looking for a bridge converter to probe and preserve bridge pointer, at this movement

^ moment ?

the host is trying to bind the all callbacks and one of the bind callback in the DSI host is trying to find the bridge using the bridge pointer in sun6i_dsi_attach call.

chipone_probe().start drm_of_find_panel_or_bridge mipi_dsi_attach sun6i_dsi_attach drm_of_find_panel_or_bridge chipone_probe().done

sun6i_dsi_probe().start mipi_dsi_host_register component_add sun6i_dsi_probe().done

However, the movement when panel defers the probe, will make the bridge converter defer the host attach call which eventually found a NULL bridge pointer during DSI component bind callback.

So, in order to prevent this scenario of binding invalid bridge, wait for DSI devices on the pipeline to probe first and start the binding process by moving component_add in host probe to attach call.

chipone_probe().start drm_of_find_panel_or_bridge mipi_dsi_attach sun6i_dsi_attach drm_of_find_panel_or_bridge component_add chipone_probe().done

sun6i_dsi_probe().start mipi_dsi_host_register sun6i_dsi_probe().done

Signed-off-by: Jagan Teki jagan@amarulasolutions.com

Changes for v6:

• none

Changes for v5:

• new patch

drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 120 +++++++++++++------------ 1 file changed, 61 insertions(+), 59 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c index 4bdcce8f1d84..9cf91dcac3f2 100644 --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c @@ -959,11 +959,63 @@ static int sun6i_dsi_dcs_read(struct sun6i_dsi *dsi, return 1; }

+static int sun6i_dsi_bind(struct device *dev, struct device *master,

• 	 void *data)
  

+{

• struct drm_device *drm = data;
• struct sun6i_dsi *dsi = dev_get_drvdata(dev);
• int ret;
• drm_encoder_helper_add(&dsi->encoder,

• 	       &sun6i_dsi_enc_helper_funcs);
  

• ret = drm_simple_encoder_init(drm, &dsi->encoder,

• 		      DRM_MODE_ENCODER_DSI);
  

• if (ret) {

• dev_err(dsi->dev, "Couldn't initialise the DSI encoder\n");
  

• return ret;
  

• }
• dsi->encoder.possible_crtcs = BIT(0);
• drm_connector_helper_add(&dsi->connector,

• 		 &sun6i_dsi_connector_helper_funcs);
  

• ret = drm_connector_init(drm, &dsi->connector,

• 		 &sun6i_dsi_connector_funcs,
  

• 		 DRM_MODE_CONNECTOR_DSI);
  

• if (ret) {

• dev_err(dsi->dev,
  

• 	"Couldn't initialise the DSI connector\n");
  

• goto err_cleanup_connector;
  

• }
• drm_connector_attach_encoder(&dsi->connector, &dsi->encoder);
• return 0;

+err_cleanup_connector:

• drm_encoder_cleanup(&dsi->encoder);
• return ret;

+}

+static void sun6i_dsi_unbind(struct device *dev, struct device *master,

• 	    void *data)
  

+{

• struct sun6i_dsi *dsi = dev_get_drvdata(dev);
• drm_encoder_cleanup(&dsi->encoder);

+}

+static const struct component_ops sun6i_dsi_ops = {

• .bind = sun6i_dsi_bind,
• .unbind = sun6i_dsi_unbind,

+};

Just use a forward declaration there, it will make the patch more straightforward.

Maxime