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Message-ID: <20755168cc2be0d1bb5e40907cfe27cea25a9363.camel@mediatek.com>
Date: Tue, 8 Feb 2022 16:20:58 +0800
From: CK Hu <ck.hu@...iatek.com>
To: AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com>,
<dri-devel@...ts.freedesktop.org>
CC: <chunkuang.hu@...nel.org>, <airlied@...ux.ie>,
<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>,
<andrzej.hajda@...el.com>, <linux-mediatek@...ts.infradead.org>,
Jagan Teki <jagan@...rulasolutions.com>,
<matthias.bgg@...il.com>, <kernel@...labora.com>,
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4] drm/mediatek: mtk_dsi: Avoid EPROBE_DEFER loop with
external bridge
Hi, Angelo:
On Mon, 2022-01-31 at 09:55 +0100, 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).
>
> Cc: <stable@...r.kernel.org> # 5.15.x
> 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);
> }
>
>
[snip]
> +
> 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);
The original would process panel. Why do you remove the panel part?
It's better that someone has a platform of DSI->Panel to test this
patch.
Regards,
CK
> + 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,
> };
>
>
[snip]
> -
> 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;
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