Hi,

On 10.12.2021 12:36, AngeloGioacchino Del Regno wrote:

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).

Signed-off-by: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com

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..2ff347da35c2 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);
  

Here we have implicit assumption that port node (0,0) points always to the 'device'. I guess it is true for now, but could bite someday. Anyway improving it  would require adding some additional helper for getting bridge based on mipi_dsi_device and should be done in separate patchset.

• 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);
• drm_bridge_remove(&dsi->bridge);
• component_del(host->dev, &mtk_dsi_component_ops);

Order should be reversed.

With this fixed:

Reviewed-by: Andrzej Hajda andrzej.hajda@intel.com

Regards

Andrzej

• 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;