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Date: Thu, 27 Jan 2022 23:21:27 +0800
From: Chun-Kuang Hu <chunkuang.hu@...nel.org>
To: AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com>
Cc: DRI Development <dri-devel@...ts.freedesktop.org>,
Chun-Kuang Hu <chunkuang.hu@...nel.org>,
David Airlie <airlied@...ux.ie>,
linux-kernel <linux-kernel@...r.kernel.org>,
andrzej.hajda@...el.com,
"moderated list:ARM/Mediatek SoC support"
<linux-mediatek@...ts.infradead.org>,
Jagan Teki <jagan@...rulasolutions.com>,
Matthias Brugger <matthias.bgg@...il.com>,
Collabora Kernel ML <kernel@...labora.com>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3] drm/mediatek: mtk_dsi: Avoid EPROBE_DEFER loop with
external bridge
Hi, Angelo:
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.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?
Regards,
Chun-Kuang.
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> Reviewed-by: Andrzej Hajda <andrzej.hajda@...el.com>
> Reviewed-by: Jagan Teki <jagan@...rulasolutions.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
>
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