The role of drm_bridge_add/remove() is more complex now after having added
the lingering list. Update the kdoc accordingly.
Also stop mentioning the global list(s) in the first line of the docs: the
most important thing to mention here is that bridges are registered and
deregistered, lists are just the type of container used to implement such
(de)registration.
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20250915-drm-bridge-debugfs-removed-v9-3-6e5c0aff5de9@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
The usefulness of /sys/kernel/debug/dri/bridges is limited as it only shows
bridges between drm_bridge_add() and drm_bridge_remove(). However
refcounted bridges can stay allocated and lingering for a long time after
drm_bridge_remove(), and a memory leak due to a missing drm_bridge_put()
would not be visible in this debugfs file.
Add lingering bridges to the /sys/kernel/debug/dri/bridges output.
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20250915-drm-bridge-debugfs-removed-v9-2-6e5c0aff5de9@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Between drm_bridge_add() and drm_bridge_remove() bridges are registered to
the DRM core via the global bridge_list and visible in
/sys/kernel/debug/dri/bridges. However between drm_bridge_remove() and the
last drm_bridge_put() memory is still allocated even though the bridge is
not registered, i.e. not in bridges_list, and also not visible in
debugfs. This prevents debugging refcounted bridges lifetime, especially
leaks due to a missing drm_bridge_put().
In order to allow debugfs to also show the removed bridges, move such
bridges into a new ad-hoc list until they are eventually freed.
Note this requires adding INIT_LIST_HEAD(&bridge->list) in the bridge
initialization code. The lack of such init was not exposing any bug so far,
but it would with the new code, for example when a bridge is allocated and
then freed without calling drm_bridge_add(), which is common on probe
errors.
drm_bridge_add() needs special care for bridges being added after having
been previously added and then removed. This happens for example for many
non-DCS DSI host bridge drivers like samsung-dsim which
drm_bridge_add/remove() themselves every time the DSI device does a DSI
attaches/detach. When the DSI device is hot-pluggable this happens multiple
times in the lifetime of the DSI host bridge. On every attach after the
first one, drm_bridge_add() finds bridge->list in the removed list, not at
the initialized state as drm_bridge_add() currently expects. Add a
list_del_init() to remove the bridge from the lingering list and bring
bridge->list back to the initialized state.
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20250915-drm-bridge-debugfs-removed-v9-1-6e5c0aff5de9@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
drm-misc-next for v6.18:
UAPI Changes:
- Add DRM_IOCTL_GEM_CHANGE_HANDLE for reassigning GEM handles
- Document DRM_MODE_PAGE_FLIP_EVENT
Cross-subsystem Changes:
fbcon:
- Add missing declarations in fbcon.h
Core Changes:
bridge:
- Fix ref counting
panel:
- Replace and remove mipi_dsi_generic_write_{seq/_chatty}()
sched:
- Fixes
Rust:
- Drop Opaque<> from ioctl arguments
Driver Changes:
amdxdma:
- Support buffers allocated by user space
- Streamline PM interfaces
- Fixes
bridge:
- cdns-dsi: Various improvements to mode setting
- Support Solomon SSD2825 plus DT bindings
- Support Waveshare DSI2DPI plus DT bindings
gud:
- Fixes
ivpu:
- Fixes
nouveau:
- Use GSP firmware by default
- Fixes
panel:
- panel-edp: Support mt8189 Chromebooks; Support BOE NV140WUM-N64;
Support SHP LQ134Z1; Fixes
- panel-simple: Support Olimex LCD-OLinuXino-5CTS plus DT bindings
- Support Samsung AMS561RA01
- Support Hydis HV101HD1 plus DT bindings
panthor:
- Print task/pid on errors
- Fixes
renesas:
- convert to RUNTIME_PM_OPS
repaper:
- Use shadow-plane helpers
rocket:
- Add driver for Rockchip NPU plus DT bindings
sharp-memory:
- Use shadow-plane helpers
simpledrm:
- Use of_reserved_mem_region_to_resource() helper
tidss:
- Use crtc_ fields for programming display mode
- Remove other drivers from aperture
v3d:
- Support querying nubmer of GPU resets for KHR_robustness
vmwgfx:
- Fixes
Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20250814072454.GA18104@linux.fritz.box
In some application scenarios, we hope to get the corresponding
connector when the bridge's detect hook is invoked.
In most cases, we can get the connector by drm_atomic_get_connector_for_encoder
if the encoder attached to the bridge is enabled, however there will
still be some scenarios where the detect hook of the bridge is called
but the corresponding encoder has not been enabled yet. For instance,
this occurs when the device is hot plug in for the first time.
Since the call to bridge's detect is initiated by the connector, passing
down the corresponding connector directly will make things simpler.
Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250703125027.311109-3-andyshrk@163.com
[DB: added the chunk to the cdn-dp driver]
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
To the best of my knowledge, all drivers in the mainline kernel adding a
DRM bridge are now converted to using devm_drm_bridge_alloc() for
allocation and initialization. Among others this ensures initialization of
the bridge refcount, allowing dynamic allocation lifetime.
devm_drm_bridge_alloc() is now mandatory for all new bridges. Code using
the old pattern ([devm_]kzalloc + filling the struct fields +
drm_bridge_add) is not allowed anymore.
Any drivers that might have been missed during the conversion, patches in
flight towards mainline and out-of-tre drivers still using the old pattern
will already be caught by a warning looking like:
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 2 PID: 83 at lib/refcount.c:25 refcount_warn_saturate+0x120/0x148
[...]
Call trace:
refcount_warn_saturate+0x120/0x148 (P)
drm_bridge_get.part.0+0x70/0x98 [drm]
drm_bridge_add+0x34/0x108 [drm]
sn65dsi83_probe+0x200/0x480 [ti_sn65dsi83]
[...]
This warning comes from the refcount code and happens because
drm_bridge_add() is increasing the refcount, which is uninitialized and
thus initially zero.
Having a warning and the corresponding stack trace is surely useful, but
the warning text does not clarify the root problem nor how to fix it.
Add a DRM_WARN() just before increasing the refcount, so the log will be
much more readable:
[drm] DRM bridge corrupted or not allocated by devm_drm_bridge_alloc()
------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
[...etc...]
A DRM_WARN is used because drm_warn and drm_WARN require a struct
drm_device pointer which is not yet available when adding a bridge.
Do not print the dev_name() in the warning because struct drm_bridge has no
pointer to the struct device. The affected driver should be easy to catch
based on the following stack trace however.
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20250620-drm-bridge-alloc-getput-drm-bridge-c-v9-3-ca53372c9a84@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Fix compile-time warnings
drivers/gpu/drm/bridge/analogix/analogix-i2c-dptx.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/bridge/analogix/analogix_dp_core.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/bridge/aux-bridge.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/bridge/aux-hpd-bridge.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/bridge/imx/imx-legacy-bridge.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/bridge/panel.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/bridge/samsung-dsim.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/bridge/synopsys/dw-hdmi.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi2.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/drm_bridge.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
drivers/gpu/drm/drm_bridge_helper.c: warning: EXPORT_SYMBOL() is used, but #include <linux/export.h> is missing
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: a934a57a42 ("scripts/misc-check: check missing #include <linux/export.h> when W=1")
Reviewed-by: André Almeida <andrealmeid@igalia.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20250612121633.229222-4-tzimmermann@suse.de
Bridges obtained via devm_drm_bridge_alloc(dev, ...) will be put when the
requesting device (@dev) is removed.
However drivers which obtained them may need to put the obtained reference
explicitly. One such case is if they bind the devm removal action to a
different device than the one implemented by the driver itself and which
might be removed at a different time, such as bridge/panel.c.
Add devm_drm_put_bridge() to manually release a devm-obtained bridge in
such cases.
This function is considered only a temporary workaround until the panel
bridge is reworked and should be removed afterwards.
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20250509-drm-bridge-convert-to-alloc-api-v3-20-b8bc1f16d7aa@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
DRM bridges are currently considered as a fixed element of a DRM card, and
thus their lifetime is assumed to extend for as long as the card
exists. New use cases, such as hot-pluggable hardware with video bridges,
require DRM bridges to be added to and removed from a DRM card without
tearing the card down. This is possible for connectors already (used by DP
MST), it is now needed for DRM bridges as well.
As a first preliminary step, make bridges reference-counted to allow a
struct drm_bridge (along with the private driver structure embedding it) to
stay allocated even after the driver has been removed, until the last
reference is put.
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250326-drm-bridge-refcount-v9-2-5e0661fe1f84@bootlin.com
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
Add a macro to allocate and initialize a DRM bridge embedded within a
private driver struct.
Compared to current practice, which is based on [devm_]kzalloc() allocation
followed by open-coded initialization of fields, this allows to have a
common and explicit API to allocate and initialize DRM bridges.
Besides being useful to consolidate bridge driver code, this is a
fundamental step in preparation for adding dynamic lifetime to bridges
based on refcount.
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250326-drm-bridge-refcount-v9-1-5e0661fe1f84@bootlin.com
Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
The drm_bridge structure contains an encoder pointer that is widely used
by bridge drivers. This pattern is largely documented as deprecated in
other KMS entities for atomic drivers.
However, one of the main use of that pointer is done in attach to just
call drm_bridge_attach on the next bridge to add it to the bridge list.
While this dereferences the bridge->encoder pointer, it's effectively
the same encoder the bridge was being attached to.
We can make it more explicit by adding the encoder the bridge is
attached to to the list of attach parameters. This also removes the need
to dereference bridge->encoder in most drivers.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250313-bridge-connector-v6-1-511c54a604fb@kernel.org
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Bridges having DRM_BRIDGE_OP_HDMI set in their ->ops are supposed to
rely on the ->supported_formats bitmask to advertise the permitted
colorspaces, including HDMI_COLORSPACE_YUV420.
However, a new flag ->ycbcr_420_allowed has been recently introduced,
which brings the necessity to require redundant and potentially
inconsistent information to be provided on HDMI bridges initialization.
Adjust ->ycbcr_420_allowed for HDMI bridges according to
->supported_formats, right before adding them to the global bridge list.
This keeps the initialization process straightforward and unambiguous,
thereby preventing any further confusion.
Fixes: 3ced1c6875 ("drm/display: bridge_connector: handle ycbcr_420_allowed")
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241224-bridge-conn-fmt-prio-v4-1-a9ceb5671379@collabora.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
For a given bridge pipeline if any bridge sets pre_enable_prev_first
flag then the pre_enable for the previous bridge will be called before
pre_enable of this bridge and opposite is done for post_disable.
These are the potential bridge flags to alter bridge init order in order
to satisfy the MIPI DSI host and downstream panel or bridge to function.
However the existing pre_enable_prev_first logic with associated bridge
ordering has broken for both pre_enable and post_disable calls.
[pre_enable]
The altered bridge ordering has failed if two consecutive bridges on a
given pipeline enables the pre_enable_prev_first flag.
Example:
- Panel
- Bridge 1
- Bridge 2 pre_enable_prev_first
- Bridge 3
- Bridge 4 pre_enable_prev_first
- Bridge 5 pre_enable_prev_first
- Bridge 6
- Encoder
In this example, Bridge 4 and Bridge 5 have pre_enable_prev_first.
The logic looks for a bridge which enabled pre_enable_prev_first flag
on each iteration and assigned the previou bridge to limit pointer
if the bridge doesn't enable pre_enable_prev_first flags.
If control found Bridge 2 is pre_enable_prev_first then the iteration
looks for Bridge 3 and found it is not pre_enable_prev_first and assigns
it's previous Bridge 4 to limit pointer and calls pre_enable of Bridge 3
and Bridge 2 and assign iter pointer with limit which is Bridge 4.
Here is the actual problem, for the next iteration control look for
Bridge 5 instead of Bridge 4 has iter pointer in previous iteration
moved to Bridge 4 so this iteration skips the Bridge 4. The iteration
found Bridge 6 doesn't pre_enable_prev_first flags so the limit assigned
to Encoder. From next iteration Encoder skips as it is the last bridge
for reverse order pipeline.
So, the resulting pre_enable bridge order would be,
- Panel, Bridge 1, Bridge 3, Bridge 2, Bridge 6, Bridge 5.
This patch fixes this by assigning limit to next pointer instead of
previous bridge since the iteration always looks for bridge that does
NOT request prev so assigning next makes sure the last bridge on a
given iteration what exactly the limit bridge is.
So, the resulting pre_enable bridge order with fix would be,
- Panel, Bridge 1, Bridge 3, Bridge 2, Bridge 6, Bridge 5, Bridge 4,
Encoder.
[post_disable]
The altered bridge ordering has failed if two consecutive bridges on a
given pipeline enables the pre_enable_prev_first flag.
Example:
- Panel
- Bridge 1
- Bridge 2 pre_enable_prev_first
- Bridge 3
- Bridge 4 pre_enable_prev_first
- Bridge 5 pre_enable_prev_first
- Bridge 6
- Encoder
In this example Bridge 5 and Bridge 4 have pre_enable_prev_first.
The logic looks for a bridge which enabled pre_enable_prev_first flags
on each iteration and assigned the previou bridge to next and next to
limit pointer if the bridge does enable pre_enable_prev_first flag.
If control starts from Bridge 6 then it found next Bridge 5 is
pre_enable_prev_first and immediately the next assigned to previous
Bridge 6 and limit assignments to next Bridge 6 and call post_enable
of Bridge 6 even though the next consecutive Bridge 5 is enabled with
pre_enable_prev_first. This clearly misses the logic to find the state
of next conducive bridge as everytime the next and limit assigns
previous bridge if given bridge enabled pre_enable_prev_first.
So, the resulting post_disable bridge order would be,
- Encoder, Bridge 6, Bridge 5, Bridge 4, Bridge 3, Bridge 2, Bridge 1,
Panel.
This patch fixes this by assigning next with previou bridge only if the
bridge doesn't enable pre_enable_prev_first flag and the next further
assign it to limit. This way we can find the bridge that NOT requested
prev to disable last.
So, the resulting pre_enable bridge order with fix would be,
- Encoder, Bridge 4, Bridge 5, Bridge 6, Bridge 2, Bridge 3, Bridge 1,
Panel.
Validated the bridge init ordering by incorporating dummy bridges in
the sun6i-mipi-dsi pipeline
Fixes: 4fb912e5e1 ("drm/bridge: Introduce pre_enable_prev_first to alter bridge init order")
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Michael Trimarchi <michael@amarulasolutions.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230328170752.1102347-1-jagan@amarulasolutions.com
Instead of having a single file with all bridge chains, list bridges
under a corresponding per-encoder debugfs directory.
While we are at it, also slightly improve the formatting of the bridge
data: split a single line entry into multiple lines, include the symbol
name of the bridge funcs and add the textual representation of the
bridge ops.
Example of the listing:
$ cat /sys/kernel/debug/dri/0/encoder-0/bridges
bridge[0]: dsi_mgr_bridge_funcs
type: [0] Unknown
ops: [0]
bridge[1]: lt9611uxc_bridge_funcs
type: [11] HDMI-A
OF: /soc@0/geniqup@9c0000/i2c@994000/hdmi-bridge@2b:lontium,lt9611uxc
ops: [7] detect edid hpd
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231203115315.1306124-3-dmitry.baryshkov@linaro.org
Instead of the per minor directories only create a single debugfs
directory for the whole device directly when the device is initialized.
For DRM devices each minor gets a symlink to the per device directory
for now until we can be sure that this isn't useful any more in any way.
Accel devices create only the per device directory and also drops the mid
layer callback to create driver specific files.
v2: cleanup accel component as well
v3: fix typo when debugfs is disabled
v4: call drm_debugfs_dev_fini() during release as well,
some kerneldoc typos fixed
v5: rebased and one more kerneldoc fix
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230829110115.3442-4-christian.koenig@amd.com
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
DRM bridges are not visible to the userspace and it may not be
immediately clear if the chain is somehow constructed incorrectly. I
have had two separate instances of a bridge driver failing to do a
drm_bridge_attach() call, resulting in the bridge connector not being
part of the chain. In some situations this doesn't seem to cause issues,
but it will if DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is used.
Add a debugfs file to print the bridge chains. For me, on this TI AM62
based platform, I get the following output:
encoder[39]
bridge[0] type: 0, ops: 0x0
bridge[1] type: 0, ops: 0x0, OF: /bus@f0000/i2c@20000000/dsi@e:toshiba,tc358778
bridge[2] type: 0, ops: 0x3, OF: /bus@f0000/i2c@20010000/hdmi@48:lontium,lt8912b
bridge[3] type: 11, ops: 0x7, OF: /hdmi-connector:hdmi-connector
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230802-drm-bridge-chain-debugfs-v4-1-7e3ae3d137c0@ideasonboard.com
DSI sink devices typically want the DSI host powered up and configured
before they are powered up. pre_enable is the place this would normally
happen, but they are called in reverse order from panel/connector towards
the encoder, which is the "wrong" order.
Add a new flag pre_enable_prev_first that any bridge can set
to swap the order of pre_enable (and post_disable) for that and the
immediately previous bridge.
Should the immediately previous bridge also set the
pre_enable_prev_first flag, the previous bridge to that will be called
before either of those which requested pre_enable_prev_first.
eg:
- Panel
- Bridge 1
- Bridge 2 pre_enable_prev_first
- Bridge 3
- Bridge 4 pre_enable_prev_first
- Bridge 5 pre_enable_prev_first
- Bridge 6
- Encoder
Would result in pre_enable's being called as Panel, Bridge 1, Bridge 3,
Bridge 2, Bridge 6, Bridge 5, Bridge 4, Encoder.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Link: https://lore.kernel.org/r/20221205173328.1395350-5-dave.stevenson@raspberrypi.com
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
