From: Luca Ceresoli <luca.ceresoli@bootlin•com>
To: Maarten Lankhorst <maarten.lankhorst@linux•intel.com>,
Maxime Ripard <mripard@kernel•org>,
Thomas Zimmermann <tzimmermann@suse•de>,
David Airlie <airlied@gmail•com>,
Simona Vetter <simona@ffwll•ch>,
Andrzej Hajda <andrzej.hajda@intel•com>,
Neil Armstrong <neil.armstrong@linaro•org>,
Robert Foss <rfoss@kernel•org>,
Laurent Pinchart <Laurent.pinchart@ideasonboard•com>,
Jonas Karlman <jonas@kwiboo•se>,
Jernej Skrabec <jernej.skrabec@gmail•com>,
Inki Dae <inki.dae@samsung•com>,
Jagan Teki <jagan@amarulasolutions•com>,
Marek Szyprowski <m.szyprowski@samsung•com>,
Marek Vasut <marex@denx•de>, Stefan Agner <stefan@agner•ch>,
Frank Li <Frank.Li@nxp•com>,
Sascha Hauer <s.hauer@pengutronix•de>,
Pengutronix Kernel Team <kernel@pengutronix•de>,
Fabio Estevam <festevam@gmail•com>
Cc: Hui Pu <Hui.Pu@gehealthcare•com>,
Ian Ray <ian.ray@gehealthcare•com>,
Thomas Petazzoni <thomas.petazzoni@bootlin•com>,
dri-devel@lists•freedesktop.org, linux-kernel@vger•kernel.org,
imx@lists•linux.dev, linux-arm-kernel@lists•infradead.org,
Luca Ceresoli <luca.ceresoli@bootlin•com>
Subject: [PATCH 19/37] drm/bridge: samsung-dsim: move drm_bridge_add() call to probe
Date: Tue, 19 May 2026 12:37:36 +0200 [thread overview]
Message-ID: <20260519-drm-bridge-hotplug-v1-19-45e2bdb3dfb4@bootlin.com> (raw)
In-Reply-To: <20260519-drm-bridge-hotplug-v1-0-45e2bdb3dfb4@bootlin.com>
This bridge driver calls drm_bridge_add() in the DSI host .attach callback
instead of in the probe function.
This works for current use cases but is problematic for supporting hotplug
of DRM bridges. The problematic case is when this DSI host is always
present while its DSI device is hot-pluggable. In such case with the
current code the DRM card will not be populated until after the DSI device
attaches to the host, which could happen a very long time after booting, or
even not happen at all.
The reason is that the previous pipeline component (the encoder in this
case) when probing cannot find the samsung-dsim bridge. What happens is:
[1 and 2 can happen in any order, same result]
1) samsung-dsim probes (does not drm_bridge_add() itself)
2) The lcdif starts probing multiple times, but
lcdif_probe
-> lcdif_load
-> lcdif_attach_bridge
-> devm_drm_of_get_bridge() returns -EPROBE_DEFER because
the samsung-dsim is not in the global bridge_list
(deferred probe pending: imx-lcdif: Cannot connect bridge)
The samsung-dsim will not drm_bridge_add() itself until a DSI device will
try to mipi_dsi_attach() to the DSI Host, which can happen arbitratily late
on hot-pluggable hardware.
As a preliminary step to supporting hotplug move drm_bridge_add() at probe
time, so that the samsung-dsim DSI host bridge is available during boot,
even without a connected DSI device. This results in:
1) samsung-dsim probes (and adds to drm_bridge_add() itself)
2) The lcdif starts probing multiple times, but
lcdif_probe
-> lcdif_load
-> lcdif_attach_bridge
-> devm_drm_of_get_bridge() --> OK, returns samsung-dsim ptr
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin•com>
---
drivers/gpu/drm/bridge/samsung-dsim.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index 2af287221e22..cefb20ec68ad 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1980,8 +1980,6 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host,
mipi_dsi_pixel_format_to_bpp(device->format),
device->mode_flags);
- drm_bridge_add(&dsi->bridge);
-
/*
* This is a temporary solution and should be made by more generic way.
*
@@ -2014,7 +2012,6 @@ static int samsung_dsim_host_attach(struct mipi_dsi_host *host,
if (!(device->mode_flags & MIPI_DSI_MODE_VIDEO))
samsung_dsim_unregister_te_irq(dsi);
err_remove_panel_bridge:
- drm_bridge_remove(&dsi->bridge);
if (dsi->panel_bridge_added) {
drm_panel_bridge_remove(next_bridge);
dsi->panel_bridge_added = false;
@@ -2040,8 +2037,6 @@ static int samsung_dsim_host_detach(struct mipi_dsi_host *host,
samsung_dsim_unregister_te_irq(dsi);
- drm_bridge_remove(&dsi->bridge);
-
return 0;
}
@@ -2242,6 +2237,8 @@ int samsung_dsim_probe(struct platform_device *pdev)
goto err_disable_runtime;
}
+ drm_bridge_add(&dsi->bridge);
+
return 0;
err_disable_runtime:
@@ -2255,6 +2252,8 @@ void samsung_dsim_remove(struct platform_device *pdev)
{
struct samsung_dsim *dsi = platform_get_drvdata(pdev);
+ drm_bridge_remove(&dsi->bridge);
+
pm_runtime_disable(&pdev->dev);
if (dsi->plat_data->host_ops && dsi->plat_data->host_ops->unregister_host)
--
2.54.0
next prev parent reply other threads:[~2026-05-19 10:39 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-19 10:37 [PATCH 00/37] drm bridge hotplug Luca Ceresoli
2026-05-19 10:37 ` [PATCH 01/37] drm/connector: split drmm_connector_hdmi_init() in 3 parts Luca Ceresoli
2026-05-19 10:37 ` [PATCH 02/37] drm/connector: add drm_connector_hdmi_dynamic_init() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 03/37] drm/display: bridge-connector: rename variable for consistency Luca Ceresoli
2026-05-19 10:37 ` [PATCH 04/37] drm/display: bridge-connector: store the drm_device pointer Luca Ceresoli
2026-05-19 10:37 ` [PATCH 05/37] drm/display: bridge-connector: split code creating the connector to a subfunction Luca Ceresoli
2026-05-19 10:37 ` [PATCH 06/37] drm/display: bridge-connector: use a drm_bridge_connector internally, not a drm_connector Luca Ceresoli
2026-05-19 10:37 ` [PATCH 07/37] drm/display: bridge-connector: extract drm_bridge_connector_get_bridges() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 08/37] drm/display: bridge-connector: return int from drm_bridge_connector_get_bridges() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 09/37] drm/display: bridge-connector: extract drm_bridge_connector_init_hdmi_audio_cec() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 10/37] drm/display: bridge-connector: return int from drm_bridge_connector_init_hdmi_audio_cec() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 11/37] drm/display: bridge-connector: return int from drm_bridge_connector_add_connector() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 12/37] drm/display: bridge-connector: hoist error management to common code Luca Ceresoli
2026-05-19 10:37 ` [PATCH 13/37] drm/display: bridge-connector: move drm_bridge_connector_put_bridges() definition eariler Luca Ceresoli
2026-05-19 10:37 ` [PATCH 14/37] drm/display: bridge-connector: add non-drmm variant of drm_bridge_connector_put_bridges() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 15/37] drm/display: bridge-connector: allocate the connector dynamically Luca Ceresoli
2026-05-19 10:37 ` [PATCH 16/37] drm/display: bridge-connector: move per-connector fields to the dynamic connector Luca Ceresoli
2026-05-19 10:37 ` [PATCH 17/37] drm/display: bridge-connector: protect dynconn creation and destruction with a mutex Luca Ceresoli
2026-05-19 10:37 ` [PATCH 18/37] drm/bridge: samsung-dsim: remove the panel_bridge on host_detach Luca Ceresoli
2026-05-19 10:37 ` Luca Ceresoli [this message]
2026-05-19 10:37 ` [PATCH 20/37] drm/bridge: samsung-dsim: attach: return -EPROBE_DEFER is next bridge not yet available Luca Ceresoli
2026-05-19 10:37 ` [PATCH 21/37] drm/bridge: initialize chain_node list head on allocation Luca Ceresoli
2026-05-19 10:37 ` [PATCH 22/37] drm/bridge: initialize chain_node list head on detach and attach errors Luca Ceresoli
2026-05-19 10:37 ` [PATCH 23/37] drm/encoder: add drm_encoder_cleanup_from() Luca Ceresoli
2026-05-19 10:37 ` [PATCH 24/37] drm/atomic: move drm_atomic_helper_disable_all() and drm_atomic_helper_shutdown() from drm_atomic_helper to drm_atomic Luca Ceresoli
2026-05-19 10:37 ` [PATCH 25/37] drm/bridge: shutdown and cleanup on bridge unplug Luca Ceresoli
2026-05-19 10:37 ` [PATCH 26/37] drm: event-notifier: add mechanism to notify about hotplug events Luca Ceresoli
2026-05-19 10:37 ` [PATCH 27/37] drm/bridge: notify about detached bridges Luca Ceresoli
2026-05-19 10:37 ` [PATCH 28/37] drm/mipi-dsi: turn DRM_MIPI_DSI into a tristate Luca Ceresoli
2026-05-19 10:37 ` [PATCH 29/37] drm/mipi-dsi: notify about DSI attach Luca Ceresoli
2026-05-19 10:37 ` [PATCH 30/37] drm/bridge: add drm_bridge_is_tail() to know whether a bridge completes the pipeline Luca Ceresoli
2026-05-19 10:37 ` [PATCH 31/37] drm/bridge: panel: implement .is_tail Luca Ceresoli
2026-05-19 15:12 ` Neil Armstrong
2026-05-19 10:37 ` [PATCH 32/37] drm/bridge: display-connector: " Luca Ceresoli
2026-05-19 10:37 ` [PATCH 33/37] drm/bridge: samsung-dsim: " Luca Ceresoli
2026-05-19 10:37 ` [PATCH 34/37] drm/bridge: ti-sn65dsi83: " Luca Ceresoli
2026-05-19 10:37 ` [PATCH 35/37] drm/bridge: drm_bridge_attach(): don't fail on -EPROBE_DEFER Luca Ceresoli
2026-05-19 10:37 ` [PATCH 36/37] drm/display: bridge-connector: handle bridge hotplug Luca Ceresoli
2026-05-19 10:37 ` [PATCH 37/37] drm/mxsfb/lcdif: enable " Luca Ceresoli
2026-06-01 15:44 ` [PATCH 00/37] drm " Luca Ceresoli
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