Re: [PATCH v3] drm/mediatek: mtk_dsi: Avoid EPROBE_DEFER loop with external bridge

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Hi, Angelo:

AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx> 於
2022年1月27日 週四 下午10:36寫道:
>
> DRM bridge drivers are now attaching their DSI device at probe time,
> which requires us to register our DSI host in order to let the bridge
> to probe: this recently started producing an endless -EPROBE_DEFER
> loop on some machines that are using external bridges, like the
> parade-ps8640, found on the ACER Chromebook R13.
>
> Now that the DSI hosts/devices probe sequence is documented, we can
> do adjustments to the mtk_dsi driver as to both fix now and make sure
> to avoid this situation in the future: for this, following what is
> documented in drm_bridge.c, move the mtk_dsi component_add() to the
> mtk_dsi_ops.attach callback and delete it in the detach callback;
> keeping in mind that we are registering a drm_bridge for our DSI,
> which is only used/attached if the DSI Host is bound, it wouldn't
> make sense to keep adding our bridge at probe time (as it would
> be useless to have it if mtk_dsi_ops.attach() fails!), so also move
> that one to the dsi host attach function (and remove it in detach).
>
> Fixes: 209264a85707 ("drm/bridge: Document the probe issue with MIPI-DSI bridges")

The fixed tag should indicate the patch which cause the bug, but why a
patch just adding document would cause bug?
So no any patch cause bug? This patch just want to prevent a possible bug?

Regards,
Chun-Kuang.

> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> Reviewed-by: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
> Reviewed-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
>
> ---
>  drivers/gpu/drm/mediatek/mtk_dsi.c | 167 +++++++++++++++--------------
>  1 file changed, 84 insertions(+), 83 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> index 5d90d2eb0019..bced4c7d668e 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> @@ -786,18 +786,101 @@ void mtk_dsi_ddp_stop(struct device *dev)
>         mtk_dsi_poweroff(dsi);
>  }
>
> +static int mtk_dsi_encoder_init(struct drm_device *drm, struct mtk_dsi *dsi)
> +{
> +       int ret;
> +
> +       ret = drm_simple_encoder_init(drm, &dsi->encoder,
> +                                     DRM_MODE_ENCODER_DSI);
> +       if (ret) {
> +               DRM_ERROR("Failed to encoder init to drm\n");
> +               return ret;
> +       }
> +
> +       dsi->encoder.possible_crtcs = mtk_drm_find_possible_crtc_by_comp(drm, dsi->host.dev);
> +
> +       ret = drm_bridge_attach(&dsi->encoder, &dsi->bridge, NULL,
> +                               DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> +       if (ret)
> +               goto err_cleanup_encoder;
> +
> +       dsi->connector = drm_bridge_connector_init(drm, &dsi->encoder);
> +       if (IS_ERR(dsi->connector)) {
> +               DRM_ERROR("Unable to create bridge connector\n");
> +               ret = PTR_ERR(dsi->connector);
> +               goto err_cleanup_encoder;
> +       }
> +       drm_connector_attach_encoder(dsi->connector, &dsi->encoder);
> +
> +       return 0;
> +
> +err_cleanup_encoder:
> +       drm_encoder_cleanup(&dsi->encoder);
> +       return ret;
> +}
> +
> +static int mtk_dsi_bind(struct device *dev, struct device *master, void *data)
> +{
> +       int ret;
> +       struct drm_device *drm = data;
> +       struct mtk_dsi *dsi = dev_get_drvdata(dev);
> +
> +       ret = mtk_dsi_encoder_init(drm, dsi);
> +       if (ret)
> +               return ret;
> +
> +       return device_reset_optional(dev);
> +}
> +
> +static void mtk_dsi_unbind(struct device *dev, struct device *master,
> +                          void *data)
> +{
> +       struct mtk_dsi *dsi = dev_get_drvdata(dev);
> +
> +       drm_encoder_cleanup(&dsi->encoder);
> +}
> +
> +static const struct component_ops mtk_dsi_component_ops = {
> +       .bind = mtk_dsi_bind,
> +       .unbind = mtk_dsi_unbind,
> +};
> +
>  static int mtk_dsi_host_attach(struct mipi_dsi_host *host,
>                                struct mipi_dsi_device *device)
>  {
>         struct mtk_dsi *dsi = host_to_dsi(host);
> +       struct device *dev = host->dev;
> +       int ret;
>
>         dsi->lanes = device->lanes;
>         dsi->format = device->format;
>         dsi->mode_flags = device->mode_flags;
> +       dsi->next_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 0, 0);
> +       if (IS_ERR(dsi->next_bridge))
> +               return PTR_ERR(dsi->next_bridge);
> +
> +       drm_bridge_add(&dsi->bridge);
> +
> +       ret = component_add(host->dev, &mtk_dsi_component_ops);
> +       if (ret) {
> +               DRM_ERROR("failed to add dsi_host component: %d\n", ret);
> +               drm_bridge_remove(&dsi->bridge);
> +               return ret;
> +       }
>
>         return 0;
>  }
>
> +static int mtk_dsi_host_detach(struct mipi_dsi_host *host,
> +                              struct mipi_dsi_device *device)
> +{
> +       struct mtk_dsi *dsi = host_to_dsi(host);
> +
> +       component_del(host->dev, &mtk_dsi_component_ops);
> +       drm_bridge_remove(&dsi->bridge);
> +       return 0;
> +}
> +
>  static void mtk_dsi_wait_for_idle(struct mtk_dsi *dsi)
>  {
>         int ret;
> @@ -938,73 +1021,14 @@ static ssize_t mtk_dsi_host_transfer(struct mipi_dsi_host *host,
>
>  static const struct mipi_dsi_host_ops mtk_dsi_ops = {
>         .attach = mtk_dsi_host_attach,
> +       .detach = mtk_dsi_host_detach,
>         .transfer = mtk_dsi_host_transfer,
>  };
>
> -static int mtk_dsi_encoder_init(struct drm_device *drm, struct mtk_dsi *dsi)
> -{
> -       int ret;
> -
> -       ret = drm_simple_encoder_init(drm, &dsi->encoder,
> -                                     DRM_MODE_ENCODER_DSI);
> -       if (ret) {
> -               DRM_ERROR("Failed to encoder init to drm\n");
> -               return ret;
> -       }
> -
> -       dsi->encoder.possible_crtcs = mtk_drm_find_possible_crtc_by_comp(drm, dsi->host.dev);
> -
> -       ret = drm_bridge_attach(&dsi->encoder, &dsi->bridge, NULL,
> -                               DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> -       if (ret)
> -               goto err_cleanup_encoder;
> -
> -       dsi->connector = drm_bridge_connector_init(drm, &dsi->encoder);
> -       if (IS_ERR(dsi->connector)) {
> -               DRM_ERROR("Unable to create bridge connector\n");
> -               ret = PTR_ERR(dsi->connector);
> -               goto err_cleanup_encoder;
> -       }
> -       drm_connector_attach_encoder(dsi->connector, &dsi->encoder);
> -
> -       return 0;
> -
> -err_cleanup_encoder:
> -       drm_encoder_cleanup(&dsi->encoder);
> -       return ret;
> -}
> -
> -static int mtk_dsi_bind(struct device *dev, struct device *master, void *data)
> -{
> -       int ret;
> -       struct drm_device *drm = data;
> -       struct mtk_dsi *dsi = dev_get_drvdata(dev);
> -
> -       ret = mtk_dsi_encoder_init(drm, dsi);
> -       if (ret)
> -               return ret;
> -
> -       return device_reset_optional(dev);
> -}
> -
> -static void mtk_dsi_unbind(struct device *dev, struct device *master,
> -                          void *data)
> -{
> -       struct mtk_dsi *dsi = dev_get_drvdata(dev);
> -
> -       drm_encoder_cleanup(&dsi->encoder);
> -}
> -
> -static const struct component_ops mtk_dsi_component_ops = {
> -       .bind = mtk_dsi_bind,
> -       .unbind = mtk_dsi_unbind,
> -};
> -
>  static int mtk_dsi_probe(struct platform_device *pdev)
>  {
>         struct mtk_dsi *dsi;
>         struct device *dev = &pdev->dev;
> -       struct drm_panel *panel;
>         struct resource *regs;
>         int irq_num;
>         int ret;
> @@ -1021,19 +1045,6 @@ static int mtk_dsi_probe(struct platform_device *pdev)
>                 return ret;
>         }
>
> -       ret = drm_of_find_panel_or_bridge(dev->of_node, 0, 0,
> -                                         &panel, &dsi->next_bridge);
> -       if (ret)
> -               goto err_unregister_host;
> -
> -       if (panel) {
> -               dsi->next_bridge = devm_drm_panel_bridge_add(dev, panel);
> -               if (IS_ERR(dsi->next_bridge)) {
> -                       ret = PTR_ERR(dsi->next_bridge);
> -                       goto err_unregister_host;
> -               }
> -       }
> -
>         dsi->driver_data = of_device_get_match_data(dev);
>
>         dsi->engine_clk = devm_clk_get(dev, "engine");
> @@ -1098,14 +1109,6 @@ static int mtk_dsi_probe(struct platform_device *pdev)
>         dsi->bridge.of_node = dev->of_node;
>         dsi->bridge.type = DRM_MODE_CONNECTOR_DSI;
>
> -       drm_bridge_add(&dsi->bridge);
> -
> -       ret = component_add(&pdev->dev, &mtk_dsi_component_ops);
> -       if (ret) {
> -               dev_err(&pdev->dev, "failed to add component: %d\n", ret);
> -               goto err_unregister_host;
> -       }
> -
>         return 0;
>
>  err_unregister_host:
> @@ -1118,8 +1121,6 @@ static int mtk_dsi_remove(struct platform_device *pdev)
>         struct mtk_dsi *dsi = platform_get_drvdata(pdev);
>
>         mtk_output_dsi_disable(dsi);
> -       drm_bridge_remove(&dsi->bridge);
> -       component_del(&pdev->dev, &mtk_dsi_component_ops);
>         mipi_dsi_host_unregister(&dsi->host);
>
>         return 0;
> --
> 2.33.1
>




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