Re: [PATCH v6 3/5] drm/vc4: Set up the DSI host at pdev probe time, not component bind.

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Tue, 15 Aug 2017 16:47:20 -0700
Eric Anholt <eric@anholt.net> wrote:

> We need the following things to happen in sequence:
> 
> DSI host creation
> DSI device creation in the panel driver (needs DSI host)
> DSI device attach from panel to host.
> DSI drm_panel_add()
> DSI encoder creation
> DSI encoder's DRM panel/bridge attach
> 
> Unless we allow device creation while the host isn't up yet, we need
> to break the -EPROBE_DEFER deadlock between the panel driver looking
> up the host and the host driver looking up the panel.  We can do so by
> moving the DSI host creation outside of the component bind loop, and
> the panel/bridge lookup/attach into the component bind process.
> 
> Signed-off-by: Eric Anholt <eric@anholt.net>

Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>

> ---
>  drivers/gpu/drm/vc4/vc4_dsi.c | 97 +++++++++++++++++++++++++------------------
>  1 file changed, 57 insertions(+), 40 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
> index 2516cd3a1d87..ec1d646b3151 100644
> --- a/drivers/gpu/drm/vc4/vc4_dsi.c
> +++ b/drivers/gpu/drm/vc4/vc4_dsi.c
> @@ -33,6 +33,7 @@
>  #include <drm/drm_crtc_helper.h>
>  #include <drm/drm_edid.h>
>  #include <drm/drm_mipi_dsi.h>
> +#include <drm/drm_of.h>
>  #include <drm/drm_panel.h>
>  #include <linux/clk.h>
>  #include <linux/clk-provider.h>
> @@ -504,7 +505,6 @@ struct vc4_dsi {
>  	struct mipi_dsi_host dsi_host;
>  	struct drm_encoder *encoder;
>  	struct drm_bridge *bridge;
> -	bool is_panel_bridge;
>  
>  	void __iomem *regs;
>  
> @@ -1289,7 +1289,6 @@ static int vc4_dsi_host_attach(struct mipi_dsi_host *host,
>  			       struct mipi_dsi_device *device)
>  {
>  	struct vc4_dsi *dsi = host_to_dsi(host);
> -	int ret = 0;
>  
>  	dsi->lanes = device->lanes;
>  	dsi->channel = device->channel;
> @@ -1324,34 +1323,12 @@ static int vc4_dsi_host_attach(struct mipi_dsi_host *host,
>  		return 0;
>  	}
>  
> -	dsi->bridge = of_drm_find_bridge(device->dev.of_node);
> -	if (!dsi->bridge) {
> -		struct drm_panel *panel =
> -			of_drm_find_panel(device->dev.of_node);
> -
> -		dsi->bridge = drm_panel_bridge_add(panel,
> -						   DRM_MODE_CONNECTOR_DSI);
> -		if (IS_ERR(dsi->bridge)) {
> -			ret = PTR_ERR(dsi->bridge);
> -			dsi->bridge = NULL;
> -			return ret;
> -		}
> -		dsi->is_panel_bridge = true;
> -	}
> -
> -	return drm_bridge_attach(dsi->encoder, dsi->bridge, NULL);
> +	return 0;
>  }
>  
>  static int vc4_dsi_host_detach(struct mipi_dsi_host *host,
>  			       struct mipi_dsi_device *device)
>  {
> -	struct vc4_dsi *dsi = host_to_dsi(host);
> -
> -	if (dsi->is_panel_bridge) {
> -		drm_panel_bridge_remove(dsi->bridge);
> -		dsi->bridge = NULL;
> -	}
> -
>  	return 0;
>  }
>  
> @@ -1493,16 +1470,13 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
>  	struct platform_device *pdev = to_platform_device(dev);
>  	struct drm_device *drm = dev_get_drvdata(master);
>  	struct vc4_dev *vc4 = to_vc4_dev(drm);
> -	struct vc4_dsi *dsi;
> +	struct vc4_dsi *dsi = dev_get_drvdata(dev);
>  	struct vc4_dsi_encoder *vc4_dsi_encoder;
> +	struct drm_panel *panel;
>  	const struct of_device_id *match;
>  	dma_cap_mask_t dma_mask;
>  	int ret;
>  
> -	dsi = devm_kzalloc(dev, sizeof(*dsi), GFP_KERNEL);
> -	if (!dsi)
> -		return -ENOMEM;
> -
>  	match = of_match_device(vc4_dsi_dt_match, dev);
>  	if (!match)
>  		return -ENODEV;
> @@ -1517,7 +1491,6 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
>  	vc4_dsi_encoder->dsi = dsi;
>  	dsi->encoder = &vc4_dsi_encoder->base.base;
>  
> -	dsi->pdev = pdev;
>  	dsi->regs = vc4_ioremap_regs(pdev, 0);
>  	if (IS_ERR(dsi->regs))
>  		return PTR_ERR(dsi->regs);
> @@ -1598,6 +1571,18 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
>  		return ret;
>  	}
>  
> +	ret = drm_of_find_panel_or_bridge(dev->of_node, 0, 0,
> +					  &panel, &dsi->bridge);
> +	if (ret)
> +		return ret;
> +
> +	if (panel) {
> +		dsi->bridge = devm_drm_panel_bridge_add(dev, panel,
> +							DRM_MODE_CONNECTOR_DSI);
> +		if (IS_ERR(dsi->bridge))
> +			return PTR_ERR(dsi->bridge);
> +	}
> +
>  	/* The esc clock rate is supposed to always be 100Mhz. */
>  	ret = clk_set_rate(dsi->escape_clock, 100 * 1000000);
>  	if (ret) {
> @@ -1616,12 +1601,11 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
>  			 DRM_MODE_ENCODER_DSI, NULL);
>  	drm_encoder_helper_add(dsi->encoder, &vc4_dsi_encoder_helper_funcs);
>  
> -	dsi->dsi_host.ops = &vc4_dsi_host_ops;
> -	dsi->dsi_host.dev = dev;
> -
> -	mipi_dsi_host_register(&dsi->dsi_host);
> -
> -	dev_set_drvdata(dev, dsi);
> +	ret = drm_bridge_attach(dsi->encoder, dsi->bridge, NULL);
> +	if (ret) {
> +		dev_err(dev, "bridge attach failed: %d\n", ret);
> +		return ret;
> +	}
>  
>  	pm_runtime_enable(dev);
>  
> @@ -1639,8 +1623,6 @@ static void vc4_dsi_unbind(struct device *dev, struct device *master,
>  
>  	vc4_dsi_encoder_destroy(dsi->encoder);
>  
> -	mipi_dsi_host_unregister(&dsi->dsi_host);
> -
>  	if (dsi->port == 1)
>  		vc4->dsi1 = NULL;
>  }
> @@ -1652,12 +1634,47 @@ static const struct component_ops vc4_dsi_ops = {
>  
>  static int vc4_dsi_dev_probe(struct platform_device *pdev)
>  {
> -	return component_add(&pdev->dev, &vc4_dsi_ops);
> +	struct device *dev = &pdev->dev;
> +	struct vc4_dsi *dsi;
> +	int ret;
> +
> +	dsi = devm_kzalloc(dev, sizeof(*dsi), GFP_KERNEL);
> +	if (!dsi)
> +		return -ENOMEM;
> +	dev_set_drvdata(dev, dsi);
> +
> +	dsi->pdev = pdev;
> +
> +	/* Note, the initialization sequence for DSI and panels is
> +	 * tricky.  The component bind above won't get past its
> +	 * -EPROBE_DEFER until the panel/bridge probes.  The
> +	 * panel/bridge will return -EPROBE_DEFER until it has a
> +	 * mipi_dsi_host to register its device to.  So, we register
> +	 * the host during pdev probe time, so vc4 as a whole can then
> +	 * -EPROBE_DEFER its component bind process until the panel
> +	 * successfully attaches.
> +	 */
> +	dsi->dsi_host.ops = &vc4_dsi_host_ops;
> +	dsi->dsi_host.dev = dev;
> +	mipi_dsi_host_register(&dsi->dsi_host);
> +
> +	ret = component_add(&pdev->dev, &vc4_dsi_ops);
> +	if (ret) {
> +		mipi_dsi_host_unregister(&dsi->dsi_host);
> +		return ret;
> +	}
> +
> +	return 0;
>  }
>  
>  static int vc4_dsi_dev_remove(struct platform_device *pdev)
>  {
> +	struct device *dev = &pdev->dev;
> +	struct vc4_dsi *dsi = dev_get_drvdata(dev);
> +
>  	component_del(&pdev->dev, &vc4_dsi_ops);
> +	mipi_dsi_host_unregister(&dsi->dsi_host);
> +
>  	return 0;
>  }
>