[PATCH v2 1/2] drm: rcar-du: mipi-dsi: Support bridge probe ordering

[Laurent Pinchart]

Hi Kieran,

Thank you for the patch.

On Tue, Nov 30, 2021 at 04:25:12PM +0000, Kieran Bingham wrote:
> The bridge probe ordering for DSI devices has been clarified and further
> documented in

I've read the document and


:-)

> To support connecting with the SN65DSI86 device after commit c3b75d4734cb
> ("drm/bridge: sn65dsi86: Register and attach our DSI device at probe"),
> update to the new probe ordering to remove a perpetual -EPROBE_DEFER
> loop between the two devices.
> 
> Signed-off-by: Kieran Bingham <kieran.bingham+renesas at ideasonboard.com>
> 
> ---
> v2
> - Remove now unused panel variable from rcar_mipi_dsi_probe()
> 
>  drivers/gpu/drm/rcar-du/rcar_mipi_dsi.c | 49 +++++++++++++------------
>  1 file changed, 26 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_mipi_dsi.c b/drivers/gpu/drm/rcar-du/rcar_mipi_dsi.c
> index 50e922328fed..0a9f197ef62c 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_mipi_dsi.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_mipi_dsi.c
> @@ -637,6 +637,8 @@ static int rcar_mipi_dsi_host_attach(struct mipi_dsi_host *host,
>  					struct mipi_dsi_device *device)
>  {
>  	struct rcar_mipi_dsi *dsi = host_to_rcar_mipi_dsi(host);
> +	struct drm_panel *panel;
> +	int ret;
>  
>  	if (device->lanes > dsi->num_data_lanes)
>  		return -EINVAL;
> @@ -644,12 +646,36 @@ static int rcar_mipi_dsi_host_attach(struct mipi_dsi_host *host,
>  	dsi->lanes = device->lanes;
>  	dsi->format = device->format;
>  
> +	ret = drm_of_find_panel_or_bridge(dsi->dev->of_node, 1, 0, &panel,
> +					  &dsi->next_bridge);
> +	if (ret) {
> +		dev_err_probe(dsi->dev, ret, "could not find next bridge\n");

dev_err_probe() should only be used in probe(), and this function isn't
guaranteed to be called at probe time only.

This isn't a big deal as the next patch fixes this, and both will be
squashed. Furthermore, rcar_mipi_dsi_host_attach() should only be called
when the DSI device gets registered, which should happen after it
registers its bridge, so I don't think we can see a probe deferral here.

Other than that the patch looks fine, I'll squash it with the DSI
driver.

> +		return ret;
> +	}
> +
> +	if (!dsi->next_bridge) {
> +		dsi->next_bridge = devm_drm_panel_bridge_add(dsi->dev, panel);
> +		if (IS_ERR(dsi->next_bridge)) {
> +			dev_err(dsi->dev, "failed to create panel bridge\n");
> +			return PTR_ERR(dsi->next_bridge);
> +		}
> +	}
> +
> +	/* Initialize the DRM bridge. */
> +	dsi->bridge.funcs = &rcar_mipi_dsi_bridge_ops;
> +	dsi->bridge.of_node = dsi->dev->of_node;
> +	drm_bridge_add(&dsi->bridge);
> +
>  	return 0;
>  }
>  
>  static int rcar_mipi_dsi_host_detach(struct mipi_dsi_host *host,
>  					struct mipi_dsi_device *device)
>  {
> +	struct rcar_mipi_dsi *dsi = host_to_rcar_mipi_dsi(host);
> +
> +	drm_bridge_remove(&dsi->bridge);
> +
>  	return 0;
>  }
>  
> @@ -731,7 +757,6 @@ static int rcar_mipi_dsi_get_clocks(struct rcar_mipi_dsi *dsi)
>  static int rcar_mipi_dsi_probe(struct platform_device *pdev)
>  {
>  	struct rcar_mipi_dsi *dsi;
> -	struct drm_panel *panel;
>  	struct resource *mem;
>  	int ret;
>  
> @@ -764,21 +789,6 @@ static int rcar_mipi_dsi_probe(struct platform_device *pdev)
>  		return PTR_ERR(dsi->rstc);
>  	}
>  
> -	ret = drm_of_find_panel_or_bridge(dsi->dev->of_node, 1, 0, &panel,
> -					  &dsi->next_bridge);
> -	if (ret) {
> -		dev_err_probe(dsi->dev, ret, "could not find next bridge\n");
> -		return ret;
> -	}
> -
> -	if (!dsi->next_bridge) {
> -		dsi->next_bridge = devm_drm_panel_bridge_add(dsi->dev, panel);
> -		if (IS_ERR(dsi->next_bridge)) {
> -			dev_err(dsi->dev, "failed to create panel bridge\n");
> -			return PTR_ERR(dsi->next_bridge);
> -		}
> -	}
> -
>  	/* Initialize the DSI host. */
>  	dsi->host.dev = dsi->dev;
>  	dsi->host.ops = &rcar_mipi_dsi_host_ops;
> @@ -786,11 +796,6 @@ static int rcar_mipi_dsi_probe(struct platform_device *pdev)
>  	if (ret < 0)
>  		return ret;
>  
> -	/* Initialize the DRM bridge. */
> -	dsi->bridge.funcs = &rcar_mipi_dsi_bridge_ops;
> -	dsi->bridge.of_node = dsi->dev->of_node;
> -	drm_bridge_add(&dsi->bridge);
> -
>  	return 0;
>  }
>  
> @@ -798,8 +803,6 @@ static int rcar_mipi_dsi_remove(struct platform_device *pdev)
>  {
>  	struct rcar_mipi_dsi *dsi = platform_get_drvdata(pdev);
>  
> -	drm_bridge_remove(&dsi->bridge);
> -
>  	mipi_dsi_host_unregister(&dsi->host);
>  
>  	return 0;

-- 
Regards,

Laurent Pinchart