Messages in this thread | | | Subject | Re: [PATCH v3] drm/mediatek: mtk_dsi: Avoid EPROBE_DEFER loop with external bridge | From | AngeloGioacchino Del Regno <> | Date | Thu, 27 Jan 2022 16:46:19 +0100 |
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Il 27/01/22 16:21, Chun-Kuang Hu ha scritto: > Hi, Angelo: > > AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> 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? >
I think you've missed my previous message on v2, so I will paste it here:
unfortunately I couldn't find a valid commit for a Fixes tag. This started being an issue at some point, when the DRM was changed to adhere to the documented probe sequence: the MediaTek DSI driver was not the only one that got broken/affected by these changes.
If you have any advice on which commit should be tagged, I'm open for any kind of suggestion.
I tried to check on other drivers which got fixed for the same behavior, for example drm/msm, but none of them had a Fixes tag. When the DRM got changed to adhere to this sequence, some drm/bridge drivers were also changed; this has created some incompatibilities with some drm drivers, including drm/msm and drm/mediatek.
This commit is not fixing a latent bug that was introduced in drm/mediatek but rather one that was induced by the new, fixed, probe flow that got recently documented - and to which drivers should adhere; failing to adhere to that will produce an endless -EPROBE_DEFER loop, due to other drivers (as mentioned, for example drm/bridge drivers) having been changed to use that probe sequence.
Regards, Angelo
> Regards, > Chun-Kuang. > >> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> >> Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com> >> Reviewed-by: Jagan Teki <jagan@amarulasolutions.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..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 >>
-- AngeloGioacchino Del Regno Software Engineer
Collabora Ltd. Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK Registered in England & Wales, no. 5513718
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