lcdif_attach_bridge() uses dev_err_probe() on all its error returns to
store a specific deferral message.
However its caller lcdif_load() calls dev_err_probe() again on error,
overwriting the specific deferral messages with a unique, unavoidably
generic, message.
Make the specific deferral message visible by using a plain 'return ret' on
the caller.
Acked-by: Liu Ying <victor.liu@nxp.com>
Link: https://patch.msgid.link/20260619-drm-lcdif-deferral-msg-v1-1-ce2392dca985@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().
Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. To achieve this, instead of
adding an explicit drm_bridge_put(), migrate to the bridge::next_bridge
pointer which is automatically put when the bridge is eventually freed.
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patch.msgid.link/20260511-drm-bridge-alloc-getput-panel_or_bridge-v6-10-f61c9e498b3f@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().
Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. To achieve this, instead of
adding an explicit drm_bridge_put(), migrate to the bridge::next_bridge
pointer which is automatically put when the bridge is eventually freed.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://patch.msgid.link/20260511-drm-bridge-alloc-getput-panel_or_bridge-v6-9-f61c9e498b3f@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().
Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. To achieve this, instead of
adding an explicit drm_bridge_put(), migrate to the bridge::next_bridge
pointer which is automatically put when the bridge is eventually freed.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://patch.msgid.link/20260511-drm-bridge-alloc-getput-panel_or_bridge-v6-7-f61c9e498b3f@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().
Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. To achieve this, instead of
adding an explicit drm_bridge_put(), migrate to the bridge::next_bridge
pointer which is automatically put when the bridge is eventually freed.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://patch.msgid.link/20260511-drm-bridge-alloc-getput-panel_or_bridge-v6-6-f61c9e498b3f@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().
Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. To achieve this, instead of
adding an explicit drm_bridge_put(), migrate to the bridge::next_bridge
pointer which is automatically put when the bridge is eventually freed.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://patch.msgid.link/20260511-drm-bridge-alloc-getput-panel_or_bridge-v6-5-f61c9e498b3f@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
This driver calls drm_of_find_panel_or_bridge() with a NULL pointer in the
@panel parameter, thus using a reduced feature set of that function.
Replace this call with the simpler of_drm_get_bridge_by_endpoint().
Since of_drm_get_bridge_by_endpoint() increases the refcount of the
returned bridge, ensure it is put on removal. Here the bridge pointer is
only stored in a temporary variable, so a cleanup action is enough.
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Link: https://patch.msgid.link/20260511-drm-bridge-alloc-getput-panel_or_bridge-v6-4-f61c9e498b3f@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
drm_of_find_panel_or_bridge() is widely used, but many callers pass NULL
into the @panel or the @bridge arguments, thus making a very partial usage
of this rather complex function.
Besides, the bridge returned in @bridge is not refcounted, thus making this
API unsafe when DRM bridge hotplug will be introduced.
Solve both issues for the cases of calls to drm_of_find_panel_or_bridge()
with a NULL @panel pointer by adding a new function that only looks for
bridges (and is thus much simpler) and increments the refcount of the
returned bridge.
The new function is identical to drm_of_find_panel_or_bridge() except it:
- handles bridge refcounting: uses of_drm_find_and_get_bridge() instead of
of_drm_find_bridge() internally to return a refcounted bridge
- is simpler to use: just takes no @panel parameter, returns the pointer
in the return value instead of a double pointer argument
- has a simpler implementation: it is equal to
drm_of_find_panel_or_bridge() after removing the code that becomes dead
when @panel == NULL
Also add this function to drm_bridge.c and not drm_of.c because it returns
bridges only.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Link: https://patch.msgid.link/20260511-drm-bridge-alloc-getput-panel_or_bridge-v6-2-f61c9e498b3f@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
shmob_drm_connector_create() can init the connector in two ways, based on
the 'if (sdev->pdata)':
1. manually in shmob_drm_connector_create(), or
2. delegating to drm_bridge_connector_init()
Whichever branch is taken, drm_connector_attach_encoder() is called
immediately after to attach the connector to the encoder.
Now drm_bridge_connector_init() calls drm_connector_attach_encoder() on the
connector so it is not needed anymore in case 2 and should be removed, but
it is still needed in case 1. Move drm_connector_attach_encoder() from the
common path to inside shmob_drm_connector_create() in order to get back to
a single drm_connector_attach_encoder() in both cases.
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://patch.msgid.link/20260423115550.444930-7-luca.ceresoli@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Currently all users of the bridge-connector must call
drm_connector_attach_encoder() immediately after a successful
drm_bridge_connector_init().
This is an unnecessary burden for users. Move the call to the end of
drm_bridge_connector_init() so all callers can be simplified.
Update documentation accordingly, rewording a bit the whole paragraph which
would otherwise become poorly readable due to the growing list of actions.
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://patch.msgid.link/20260423-drm-bridge-connector-attach_encoder-v2-1-2ae6ca69b390@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
of_drm_find_bridge() is deprecated. Move to its replacement
of_drm_find_and_get_bridge() which gets a bridge reference, and ensure it
is put when done.
We need to handle the two cases: when a panel_bridge is added and when it
isn't. So:
* in the 'else' case a panel_bridge is not added and bridge is found: use
of_drm_find_and_get_bridge() to get a reference to the found bridge
* in the 'then' case a panel_bridge is found using a devm function which
already takes a refcount and will put it on removal, but we need to take
another so the following code in this function always get exactly one
reference that it needs to put
In order to put the reference, add the needed drm_bridge_put() calls in the
existing cleanup function.
Reviewed-by: Linus Walleij <linusw@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Link: https://patch.msgid.link/20260409-drm-bridge-alloc-getput-drm_of_find_bridge-4-v5-2-d7381c07788a@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
of_drm_find_bridge() is deprecated. Move to its replacement
of_drm_find_and_get_bridge() which gets a bridge reference, and ensure it
is put when done.
This is made somewhat simpler by the fact that 'bridge' is a local
variable.
However we need to handle both branches of the main if().
In the 'else' case, just switch to of_drm_find_and_get_bridge() to ensure
the bridge is not freed while in use in the function tail
(drm_bridge_attach() mainly).
In the 'then' case, devm_drm_panel_bridge_add_typed() already increments
the refcount using devres which ties the bridge allocation lifetime to the
device lifetime, so we would not need to do anything. However to have the
same behaviour in both branches take an additional reference here, so that
the bridge needs to be put whichever branch is taken without more
complicated logic.
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Tested-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Link: https://patch.msgid.link/20260409-drm-bridge-alloc-getput-drm_of_find_bridge-4-v5-1-d7381c07788a@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Take the encoder chain mutex while iterating over the encoder chain in
drm_atomic_bridge_chain_pre_enable() and
drm_atomic_bridge_chain_post_disable() to ensure the lists won't change
while being inspected.
These functions have nested list_for_each_*() loops, which makes them
complicated. list_for_each_entry_from() loops could be replaced by
drm_for_each_bridge_in_chain_from(), but it would not work in a nested way
in its current implementation. Besides, there is no "_reverse" variant of
drm_for_each_bridge_in_chain_from().
Keep code simple and readable by explicitly locking around the outer
loop. Thankfully there are no break or return points inside the loops, so
the change is trivial and readable.
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Link: https://patch.msgid.link/20260324-drm-bridge-alloc-encoder-chain-mutex-v5-7-8bf786c5c7e6@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
These loops in drm_bridge.c iterate over the encoder chain using
list_for_each_entry_reverse(), which does not prevent changes to the bridge
chain while iterating over it.
Take the encoder chain mutex while iterating to avoid chain changes while
iterating.
All the "simple" loops are converted. drm_atomic_bridge_chain_pre_enable()
and drm_atomic_bridge_chain_post_disable() are handled by a separate
commit.
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Link: https://patch.msgid.link/20260324-drm-bridge-alloc-encoder-chain-mutex-v5-6-8bf786c5c7e6@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
These loops in drm_bridge.c iterate over the encoder chain using
list_for_each_entry_from(), which does not prevent changes to the bridge
chain while iterating over it.
Convert most of those loops to instead use
drm_for_each_bridge_in_chain_from(), which locks the chain.
This also simplifies code.
All the "simple" loops are converted here. The only ones not touched are
those in drm_atomic_bridge_chain_pre_enable() and
drm_atomic_bridge_chain_post_disable(), because they have nested loops
which are not well handled by drm_for_each_bridge_in_chain_from(). Those
two functions are handled by a separate commit.
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Link: https://patch.msgid.link/20260324-drm-bridge-alloc-encoder-chain-mutex-v5-5-8bf786c5c7e6@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
drm_for_each_bridge_in_chain_scoped() and
drm_for_each_bridge_in_chain_from() currently get/put the bridge at each
iteration. But they don't protect the encoder chain, so it could change
(bridges added/removed) while some code is iterating over the list
itself. Such code can then derail on incorrect pointers.
To make iterations safe, augment these for_each macros to lock the encoder
chain mutex at the beginning and unlock it at the end of the loop (be it at
the end of the list, or earlier due to a 'break' or 'return' statement).
This change requires more operations when starting and ending the loop. To
avoid making the macros even more complex, move these operations to helper
functions. Also remname some of the existing helper functions for
consistency.
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Link: https://patch.msgid.link/20260324-drm-bridge-alloc-encoder-chain-mutex-v5-4-8bf786c5c7e6@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
drm_encoder_cleanup() modifies the encoder chain by removing bridges via
drm_bridge_detach(). Protect this whole operation by taking the mutex, so
that:
* any users iterating over the chain will not access it during the change
* other code willing to modify the list (drm_bridge_attach()) will wait
until drm_encoder_cleanup() is done
Note that the _safe macro in use here is providing a different and
orthogonal kind of protection than the mutex:
1. list_for_each_entry_safe() allows removing the current entry from the
list it is iterating on, synchronously; the non-safe version would be
unable to find the next entry after the current entry has been removed
2. the mutex being added allows to ensure that the list is not used
asynchronously by other code while it is being modified; this prevents
such other concurrent code to derail because it is iterating over an
element while it is removed
The _safe macro, which works by taking the "next" pointer in addition to
the "current" one, does not even try to provide the protection at item 2
above. This is visible e.g. when the "next" element is removed by other
concurrent code. This is what would happen without the added mutex:
1. start loop: list_for_each_entry_safe(pos, n, ...) sets:
pos = list_first_entry() = (bridge 1)
n = list_next_entry(pos) = (bridge 2)
2. enter the loop 1st time, do something with *pos (bridge 1)
3. in the meanwhile bridge 2 is hot-unplugged
-> another thread removes bridge 2
-> drm_bridge_detach()
-> list_del() sets (bridge 2)->next = LIST_POISON1
4. loop iteration 1 finishes, list_for_each_entry_safe() sets:
pos = n (previously set to bridge 2)
n = (bridge 2)->next = LIST_POISON1
5. enter the loop 2nd time, do something with *pos (bridge 2)
6. loop iteration 2 finishes, list_for_each_entry_safe() sets:
pos = n = LIST_POISON1 ==> bug!
However, simply adding mutex_[un]lock(&encoder->bridge_chain_mutex)
before/after the list_for_each_entry_safe() seems a simple and good
solution, but it is introducing a possible ABBA deadlock (found by
PROVE_LOCKING). The two code paths involved are:
* drm_encoder_cleanup():
- takes the bridge_chain_mutex (A)
- calls drm_bridge_detach -> drm_atomic_private_obj_fini ->
DRM_MODESET_LOCK_ALL_BEGIN() which takes all locks in the
acquisition context (B)
* drm_mode_getconnector() (and other code paths):
- calls drm_helper_probe_single_connector_modes() which:
- takes a drm_modeset_lock in the acquisition context (B)
- calls __drm_helper_update_and_validate ->
drm_bridge_chain_mode_valid -> drm_for_each_bridge_in_chain_from()
which takes the bridge_chain_mutex (A)
To avoid this potential ABBA deadlock, move all list items to a temporary
list while holding the bridge_chain_mutex, then detach all elements from
the temporary list without the mutex.
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Link: https://patch.msgid.link/20260324-drm-bridge-alloc-encoder-chain-mutex-v5-2-8bf786c5c7e6@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Convert this driver to DRM_BRIDGE_ATTACH_NO_CONNECTOR and to the
drm_bridge_connector framework which is the current DRM bridge best
practice.
Based on the in-tree dts[i] files this introduces no regression. Based on
the kernel doc of drm_bridge_connector.c:
* To make use of this helper, all bridges in the chain shall report bridge
* operation flags (&drm_bridge->ops) and bridge output type
* (&drm_bridge->type), as well as the DRM_BRIDGE_ATTACH_NO_CONNECTOR attach
* flag (none of the bridges shall create a DRM connector directly).
and each of the 3 LCDIF blocks in the i.MX8MP, all of them comply with the
above requirement:
* For the LCDIF3, the pipeline is:
LCDIF3 -> fsl,imx8mp-hdmi-pvi -> fsl,imx8mp-hdmi-tx -> HDMI connector
And the involved bridges are:
* fsl,imx8mp-hdmi-pvi has ops = 0 (it doesn't set it) because it
implements none the optional features mentioned by those flags, and it
honors the DRM_BRIDGE_ATTACH_NO_CONNECTOR by propagating it
* fsl,imx8mp-hdmi-tx is implemented based on dw-hdmi, which sets ops as
appropriate and also propagates the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag
* display-connector (enabled via the DT overlay if needed) sets ops and
makes DRM_BRIDGE_ATTACH_NO_CONNECTOR mandatory
* The LCDIF2 involves the panel-bridge, display-connector and lvds-decoder
(even though only the pane-bridge is currently supported), and all these
three also set ops as needed and propagate
DRM_BRIDGE_ATTACH_NO_CONNECTOR or make it mandatory.
* The LCDIF1 is used with the adv7511, tc358767 and the panel bridge
drivers which also comply with the requirements.
Tested-by: Martyn Welch <martyn.welch@collabora.com>
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com> # TQMa8MPxL/MBa8MPxL
Reviewed-by: Liu Ying <victor.liu@nxp.com>
Link: https://patch.msgid.link/20260407-drm-lcdif-dbanc-v4-11-247a16e61ef9@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
The imx8mp-hdmi-tx one of many drivers based on dw-hdmi. dw-hdmi in turn
can operate in two different modes, depending on the platform data as set
by the driver:
A. hdmi->plat_data->output_port = 0:
the HDMI output (port@1) in device tree is not used [0]
B. hdmi->plat_data->output_port = 1:
the HDMI output (port@1) is parsed to find the next bridge
The imx8mp-hdmi-tx driver falls in case A. Switching to case B, which is
the current best practice, requires that the HDMI connector is always
described in the live device tree, and a previous commit ensured this is
always the case by adding an overlay in case the device tree does not
comply.
So now we can simply switch to the new mode and support
DRM_BRIDGE_ATTACH_NO_CONNECTOR.
Reviewed-by: Liu Ying <victor.liu@nxp.com>
Link: https://patch.msgid.link/20260407-drm-lcdif-dbanc-v4-10-247a16e61ef9@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Describing the HDMI connector in device tree is recommended. While the
overlay insertion is a workaround to avoid breaking existing devices, every
dts should be improved by adding a connector description.
Add a warning to make users aware as far as possible.
As a warning line cannot hold all the relevant info, add a detailed comment
in the code so it easy to find when the warning is seen.
Reviewed-by: Liu Ying <victor.liu@nxp.com>
Link: https://patch.msgid.link/20260407-drm-lcdif-dbanc-v4-9-247a16e61ef9@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
The imx8mp-hdmi-tx is one of many drivers based on dw-hdmi. dw-hdmi in turn
can operate in two different modes, depending on the platform data as set
by the driver:
A. hdmi->plat_data->output_port = 0:
the HDMI output (port@1) in device tree is not used [0]
B. hdmi->plat_data->output_port = 1:
the HDMI output (port@1) is parsed to find the next bridge
The imx8mp-hdmi-tx driver falls in case A. This implies next_bridge will
always be NULL, and so dw_hdmi_bridge_attach() [1] will always fail if
called with the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag.
In fact case A assumes that DRM_BRIDGE_ATTACH_NO_CONNECTOR is not set and
in that case it adds an HDMI Type A connector programmatically at bridge
attach time.
Support for DRM_BRIDGE_ATTACH_NO_CONNECTOR is implemented by dw-hdmi.c in
case B. However switching to base B requires that port@1 is connected to a
"next bridge" DT node, typically the HDMI connector, because dw-hdmi won't
add the connector when using DRM_BRIDGE_ATTACH_NO_CONNECTOR.
Many dts files for imx8mp-based boards in the kernel have such a connector
described and linked to port@1, so the pipeline will be fully attached up
to a display-connector and a drm_connector added by the
bridge-connector. Sadly some of those dts files don't have the connector
described. Adding it would solve the problem easily, but this would break
existing devices which do not update the dtb when upgrading to a newer
kernel.
In preparation for switching to case B while preserving backward
compatibility for such devices, introduce a module adding the
hdmi-connector node to the live device tree at init time. This will allow
the dw-hdmi code to find the next bridge (the one wrapping the
hdmi-connector) and let the pipeline work as before.
The module is inserted only if there is no endpoint in port@1. So boards
whose device tree describe the connector will not have the device tre
modified, and will start isntantiating the correct HDMI connector type as
described in the device tree.
For boards lacking a connector description in DT the overlay will be added,
abd the HDMI connector will be Type A, which is a reasonable fallback and
is what the driver is currently doing.
[0] https://elixir.bootlin.com/linux/v7.0-rc1/source/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c#L3310
[1] https://elixir.bootlin.com/linux/v7.0-rc1/source/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c#L2907
Reviewed-by: Liu Ying <victor.liu@nxp.com>
Link: https://patch.msgid.link/20260407-drm-lcdif-dbanc-v4-8-247a16e61ef9@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
This driver looks up the next_bridge at probe time and stores it in
hdmi->bridge.next_bridge, but only uses the stored value when attaching,
and only in the DRM_BRIDGE_ATTACH_NO_CONNECTOR case.
This will be problematic with an upcoming change, adding an hdmi-connector
using a device tree overlay when not present. That change is in turn
necessary to migrate the i.MX LCDIF driver to the bridge-connector.
The problem is that, adding the hdmi-connector via an overlay, devlink
considers hdmi-connector a consumer of the dw-hdmi device, generating a
chicken-egg problem:
* hdmi-connector probe won't be tried until dw-hdmi is probed (devlink)
* dw-hdmi probe will defer until it finds the next_bridge (the
hdmi-connector wrapper bridge)
In preparation for those changes, move the next_bridge lookup from probe to
attach, when it is actually used. This allows dw-hdmi to probe, so that the
hdmi-connector can probe as well.
Also avoid storing the pointer in hdmi->bridge.next_bridge: the value is
computed when needed, thus a local variable is enough.
Finally, this also allows to slightly improve the code by not doing any DT
lookup in the !DRM_BRIDGE_ATTACH_NO_CONNECTOR case.
Tested-by: Martyn Welch <martyn.welch@collabora.com>
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com> # TQMa8MPxL/MBa8MPxL
Acked-by: Liu Ying <victor.liu@nxp.com>
Tested-by: Damon Ding <damon.ding@rock-chips.com> # rk3399
Link: https://patch.msgid.link/20260407-drm-lcdif-dbanc-v4-7-247a16e61ef9@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
dw-hdmi can operate in two different modes, depending on the platform data
as set by the driver:
A. hdmi->plat_data->output_port = 0:
the HDMI output (port@1) in device tree is not used
B. hdmi->plat_data->output_port = 1:
the HDMI output (port@1) is parsed to find the next bridge
Only case B is supported when the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag is
passed to the attach callback. Emit a warning when this is violated. Also
return -EINVAL which would be returned by drm_bridge_attach() right after
anyway.
Reviewed-by: Liu Ying <victor.liu@nxp.com>
Tested-by: Martyn Welch <martyn.welch@collabora.com>
Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com> # TQMa8MPxL/MBa8MPxL
Tested-by: Damon Ding <damon.ding@rock-chips.com> # rk3399
Link: https://patch.msgid.link/20260407-drm-lcdif-dbanc-v4-6-247a16e61ef9@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
drm_bridge_get and drm_bridge_put() do nothing when they are passed a NULL
pointer, and they do so since their initial addition in commit 30d1b37d4c
("drm/bridge: add support for refcounting").
This allows simpler code in various places when using these
functions. However it's not documented, so it's not clear whether it is
part of the API "contract" or just a current implementation detail that
might change in the future.
There is no visible reason to remove this NULL check, so document it,
making it part of the contract, letting users count on it.
Reviewed-by: Liu Ying <victor.liu@nxp.com>
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Link: https://patch.msgid.link/20260324-drm-bridge-alloc-getput-document-null-check-v1-1-fb0877c49d7e@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
of_drm_find_bridge() is deprecated. Move to its replacement
of_drm_find_and_get_bridge() which gets a bridge reference, and ensure it
is put when done.
omapdss_device_init_output() can take one bridge pointer in out->bridge or
two pointers in out->bridge and out->next_bridge. Ensure each has a
corresponding drm_bridge_get() and add drm_bridge_put() calls in the
cleanup code.
Also slightly change the initial code assigning out->panel and out->bridge
to ensure and clarify that either out->panel or out->bridge is set in the
function prologue, not both. If both were set, the 'if (out->panel){...}'
code that follows would overwrite out->bridge without having put the
reference.
Finally, take a reference in case a panel_bridge is added using
drm_panel_bridge_add(). This ensures we always need to put a reference,
which came either from of_drm_find_and_get_bridge() or by the
drm_panel_bridge_add+drm_bridge_get() branch.
Reviewed-by: Louis Chauvet <louis.chauvet@bootlin.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Link: https://patch.msgid.link/20260402-drm-bridge-alloc-getput-drm_of_find_bridge-4-v4-4-421781c8c061@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Drivers having a struct drm_bridge pointer pointing to a bridge in many
cases hold that reference until the owning device is removed. In those
cases the reference to the bridge can be put in the .remove callback
(possibly using devm actions) or in the .destroy func (possibly with the
help of struct drm_bridge::next_bridge). At those moments the driver should
not be operating anymore and won't dereference the bridge pointer after it
is put.
However there are cases when drivers need to stop holding a reference to a
bridge even when their device is not being removed. This is the case for
bridge hot-unplug, when a bridge is removed but the previous entity (bridge
or encoder) is staying. In such case the "previous entity" needs to put it
but cannot do it via devm or .destroy, because it is not being removed.
The easy way to dispose of such pointer is:
drm_bridge_put(my_priv->some_bridge);
my_priv->some_bridge = NULL;
However this is risky because there is a time window between the two lines
where the reference is put, and thus the bridge could be deallocated, but
the pointer is still assigned. If other functions of the same driver were
invoked concurrently they might dereference my_priv->some_bridge during
that window, resulting in use-after-free.
A correct solution is to clear the pointer before putting the reference,
but that needs a temporary variable:
struct drm_bridge *temp = my_priv->some_bridge;
my_priv->some_bridge = NULL;
drm_bridge_put(temp);
This solution is however annoying to write, so the incorrect version might
still sneak in.
Add a simple, easy to use function to put a bridge after setting its
pointer to NULL in the correct way.
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://patch.msgid.link/20260310-drm-bridge-atomic-vs-remove-clear_and_put-v2-1-51fe222f3cf0@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Dual LVDS output (available on the SN65DSI84) requires HSYNC_PULSE_WIDTH
and HORIZONTAL_BACK_PORCH to be divided by two with respect to the values
used for single LVDS output.
While not clearly stated in the datasheet, this is needed according to the
DSI Tuner [0] output. It also makes sense intuitively because in dual LVDS
output two pixels at a time are output and so the output clock is half of
the pixel clock.
Some dual-LVDS panels refuse to show any picture without this fix.
Divide by two HORIZONTAL_FRONT_PORCH too, even though this register is used
only for test pattern generation which is not currently implemented by this
driver.
[0] https://www.ti.com/tool/DSI-TUNER
Fixes: ceb515ba29 ("drm/bridge: ti-sn65dsi83: Add TI SN65DSI83 and SN65DSI84 driver")
Cc: stable@vger.kernel.org
Reviewed-by: Marek Vasut <marek.vasut@mailbox.org>
Link: https://patch.msgid.link/20260226-ti-sn65dsi83-dual-lvds-fixes-and-test-pattern-v1-2-2e15f5a9a6a0@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
The DSI frequency must be in the range:
(CHA_DSI_CLK_RANGE * 5 MHz) <= DSI freq < ((CHA_DSI_CLK_RANGE + 1) * 5 MHz)
So the register value should point to the lower range value, but
DIV_ROUND_UP() rounds the division to the higher range value, resulting in
an excess of 1 (unless the frequency is an exact multiple of 5 MHz).
For example for a 437100000 MHz clock CHA_DSI_CLK_RANGE should be 87 (0x57):
(87 * 5 = 435) <= 437.1 < (88 * 5 = 440)
but current code returns 88 (0x58).
Fix the computation by removing the DIV_ROUND_UP().
Fixes: ceb515ba29 ("drm/bridge: ti-sn65dsi83: Add TI SN65DSI83 and SN65DSI84 driver")
Cc: stable@vger.kernel.org
Reviewed-by: Marek Vasut <marek.vasut@mailbox.org>
Link: https://patch.msgid.link/20260226-ti-sn65dsi83-dual-lvds-fixes-and-test-pattern-v1-1-2e15f5a9a6a0@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
This driver obtains a bridge pointer from of_drm_find_bridge() in the probe
function and stores it until driver removal. of_drm_find_bridge() is
deprecated, so move to of_drm_find_and_get_bridge() for the bridge to be
refcounted and use bridge->next_bridge to put the reference on
deallocation.
To keep the code as simple and reliable as possible remove the intermediate
next_bridge and selected_bridge variables.
Get/put operations on the remaining pointer is pl->bridge.next_bridge,
which is tied to the struct imx8qxp_pixel_link lifetime, are:
- get reference when assigned (by of_drm_find_and_get_bridge())
- put reference before reassignment if reassignment happens
- put reference when the struct imx8qxp_pixel_link embedding the
struct drm_bridge is destroyed (struct drm_bridge::next_bridge)
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Acked-by: Liu Ying <victor.liu@nxp.com>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Link: https://lore.kernel.org/r/20260211-drm-bridge-alloc-getput-drm_of_find_bridge-v6-1-651ddfd13bdb@bootlin.com
of_drm_find_bridge() is deprecated. Move to its replacement
of_drm_find_and_get_bridge() which gets a bridge reference, and ensure it
is put when done.
We need to handle the two cases: when a panel is found and when it isn't,
even though the latter is not supported. So:
* in case a panel is not found and bridge is, get a reference to the
found bridge
* in case a panel is found, get a reference to the panel_bridge when it
is added, so the following code always get exactly one reference that
it needs to put
Finally, use the next_bridge pointer in struct drm_bridge in order to
simplify putting the reference.
Reviewed-by: Linus Walleij <linusw@kernel.org>
Link: https://patch.msgid.link/20260131-drm-bridge-alloc-getput-drm_of_find_bridge-4-v2-4-e081bcdc1467@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
mcde_dsi_bind() has a loop over all subnodes looking for a panel, but does
not exit when a match is found and only stores the last match. However this
will be problematic when introducing refcounting on the struct drm_device
pointer in a following commit, because of_drm_find_and_get_bridge() would
get a reference to multiple bridges.
There seem to be no real reason for looking for multiple panels, so just
break as soon as a match is found.
Reviewed-by: Linus Walleij <linusw@kernel.org>
Link: https://patch.msgid.link/20260131-drm-bridge-alloc-getput-drm_of_find_bridge-4-v2-3-e081bcdc1467@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
imx8qxp_pixel_link_find_next_bridge() uses a sophisticated logic to find
the preferred next bridge, using an array with two supporting index
variables. This is more sophisticated than required because we only ever
need a pointer to the "current" bridge and to the "best so far" bridge.
Additionally this logic is going to make the addition of proper refcounting
quite complex.
Rewrite the logic using two drm_bridge pointers, which is by itself
slightly simpler and is a preparation step for introducing bridge
refcounting in a later commit.
Also reword a comment to make it clearer.
Reviewed-by: Liu Ying <victor.liu@nxp.com>
Link: https://patch.msgid.link/20260107-drm-bridge-alloc-getput-drm_of_find_bridge-v4-1-a62b4399a6bf@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Luca Ceresoli