[PATCH 0/4] i.MX LDB DT cleanups

[PATCH 0/4] i.MX LDB DT cleanups

[Marco Felsch]

Hi,

this cleanup prepares the LDB dt-bindings for the upcoming i.MX93 and
i.MX94 LDB support and is a different abborach than [1]. This approach
should be easier to maintain [2] and far more flexible for upcoming
BLK-CTRL or IOMUX_GPR syscon sub-devices.

Please be informed: I didn't do runtime tests but since the LDB driver
never used the reg (nor reg-names) property, it should be safe to remove
them.

Regards,
  Marco

[1] https://lore.kernel.org/all/20260329-fsl_ldb_schema_fix-v1-1-351372754bc0@nxp.com/
[2] https://lore.kernel.org/all/2mkih6id2cfqjfksfvvitzlcnyfz7r4rs4f7bhtvdhf7scwzue@bb4ucnfxa4l4/#t

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
---
Marco Felsch (4):
      Revert "dt-bindings: display: bridge: ldb: Add check for reg and reg-names"
      Revert "dt-bindings: display: bridge: ldb: Fill in reg property"
      ARM: dts: imx6sx: remove LDB reg property
      arm64: dts: imx8mp: remove LDB reg and reg-names property

 .../bindings/display/bridge/fsl,ldb.yaml           | 25 +---------------------
 arch/arm/boot/dts/nxp/imx/imx6sx.dtsi              |  3 +--
 arch/arm64/boot/dts/freescale/imx8mp.dtsi          |  4 +---
 3 files changed, 3 insertions(+), 29 deletions(-)
---
base-commit: 254f49634ee16a731174d2ae34bc50bd5f45e731
change-id: 20260504-v7-1-topic-ldb-fixes-8b3042dc50de

Best regards,
-- 
Marco Felsch <m.felsch@pengutronix.de>

[PATCH 1/4] Revert "dt-bindings: display: bridge: ldb: Add check for reg and reg-names"

[Marco Felsch]

This reverts commit 8aa2f0ac08d3b207ba54e98698c9d696b86452a7.

The LDB is either part of the IOMUX_GPR (i.MX6SX) or the BLKCTRL
(i.MX8MP, i.MX93) register space. Both IOMUX_GPR and BLKCTRL are
register ranges with loose register definitions. E.g.

  - On the i.MX8MP there is one register which controls the AXI
    threshold for two different IPs (BIT(31:16) - IP1, BIT(15:0) - IP2).
  - On the i.MX6SX IOMUXC_GPR5 controlls: CSI2 mux, WDOG3 settings, PXP
    handshake, ...

In conclusion: it can't be ensured that one register belongs to one
dedicated IP and the LDB is rather an exception than the rule.

Therefore remove the 'reg' and 'reg-names' property requirement.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
---
 Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
index 7f380879fffdfef28d9a35d7fbf87fdf28377b43..828b7a40e9b6cf27f76d1cd3009505b03cbe09f1 100644
--- a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
@@ -68,7 +68,6 @@ required:
   - compatible
   - clocks
   - ports
-  - reg
 
 allOf:
   - if:
@@ -83,15 +82,6 @@ allOf:
         ports:
           properties:
             port@2: false
-  - if:
-      not:
-        properties:
-          compatible:
-            contains:
-              const: fsl,imx6sx-ldb
-    then:
-      required:
-        - reg-names
 
   - if:
       properties:

-- 
2.47.3

[PATCH 2/4] Revert "dt-bindings: display: bridge: ldb: Fill in reg property"

[Marco Felsch]

This reverts commit 16c8d76abe83d75b578d72ee22d25a52c764e14a.

Remove the 'reg' and 'reg-names' property from the LDB.

The LDB is either part of the IOMUX_GPR (i.MX6SX) or the BLKCTRL
(i.MX8MP, i.MX93) register space. Both IOMUX_GPR and BLKCTRL are
register ranges with loose register definitions. E.g.

  - On the i.MX8MP there is one register which controls the AXI
    threshold for two different IPs (BIT(31:16) - IP1, BIT(15:0) - IP2).
  - On the i.MX6SX IOMUXC_GPR5 controlls: CSI2 mux, WDOG3 settings, PXP
    handshake, ...

In conclusion: it can't be ensured that one register belongs to one
dedicated IP and the LDB is rather an exception than the rule.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
---
 .../devicetree/bindings/display/bridge/fsl,ldb.yaml       | 15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
index 828b7a40e9b6cf27f76d1cd3009505b03cbe09f1..e04df77af756f1dc46fc098d765502d44cc2de00 100644
--- a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
@@ -27,14 +27,6 @@ properties:
   clock-names:
     const: ldb
 
-  reg:
-    maxItems: 2
-
-  reg-names:
-    items:
-      - const: ldb
-      - const: lvds
-
   nxp,enable-termination-resistor:
     type: boolean
     description:
@@ -99,15 +91,10 @@ examples:
     #include <dt-bindings/clock/imx8mp-clock.h>
 
     blk-ctrl {
-        #address-cells = <1>;
-        #size-cells = <1>;
-
-        bridge@5c {
+        bridge {
             compatible = "fsl,imx8mp-ldb";
             clocks = <&clk IMX8MP_CLK_MEDIA_LDB>;
             clock-names = "ldb";
-            reg = <0x5c 0x4>, <0x128 0x4>;
-            reg-names = "ldb", "lvds";
 
             ports {
                 #address-cells = <1>;

-- 
2.47.3

[PATCH 3/4] ARM: dts: imx6sx: remove LDB reg property

[Marco Felsch]

The iomux-gpr syscon device has a very loose register definition. Many
registers have a multi purpose, e.g. one register controlls the WDG
behavior and the CSI2 mux settings. This would lead into multiple
sub-devices which use the same 'reg' which is wrong.

Instead of specifying the 'reg' in the OF each sub-device driver needs
to handle the correct bits on their own. Therefore drop the 'reg'
porperty from the bridge node as well as the @18 register suffix.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
---
 arch/arm/boot/dts/nxp/imx/imx6sx.dtsi | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm/boot/dts/nxp/imx/imx6sx.dtsi b/arch/arm/boot/dts/nxp/imx/imx6sx.dtsi
index aefae5a3a6bebd43c67070376196db559d0d20cb..4b974b54195950e8bd2ef6d590f3530b2a43106e 100644
--- a/arch/arm/boot/dts/nxp/imx/imx6sx.dtsi
+++ b/arch/arm/boot/dts/nxp/imx/imx6sx.dtsi
@@ -850,9 +850,8 @@ gpr: syscon@20e4000 {
 				#size-cells = <1>;
 				reg = <0x020e4000 0x4000>;
 
-				lvds_bridge: bridge@18 {
+				lvds_bridge: bridge {
 					compatible = "fsl,imx6sx-ldb";
-					reg = <0x18 0x4>;
 					clocks = <&clks IMX6SX_CLK_LDB_DI0>;
 					clock-names = "ldb";
 					status = "disabled";

-- 
2.47.3

[PATCH 4/4] arm64: dts: imx8mp: remove LDB reg and reg-names property

[Marco Felsch]

The blk-ctrl syscon device(s) have a very loose register definition, e.g
one register configures the USB PHY clock source, the PCIe EP ready bit
and enables PCIe and USB clocks. This would lead into multiple
sub-devices which use the same 'reg' which is wrong.

Instead of specifying the 'reg' in the OF each sub-device driver needs
to handle the correct bits on their own. Therefore drop the 'reg' and
'reg-names' porperty from the bridge node as well as the '@5c' register
suffix.

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
---
 arch/arm64/boot/dts/freescale/imx8mp.dtsi | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/arm64/boot/dts/freescale/imx8mp.dtsi b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
index 90d7bb8f5619e50d9fd65bcf18c083affe15e6f9..41649afff813833aeb1c0355827597578048b037 100644
--- a/arch/arm64/boot/dts/freescale/imx8mp.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
@@ -1999,10 +1999,8 @@ media_blk_ctrl: blk-ctrl@32ec0000 {
 						       <1039500000>;
 				#power-domain-cells = <1>;
 
-				lvds_bridge: bridge@5c {
+				lvds_bridge: bridge {
 					compatible = "fsl,imx8mp-ldb";
-					reg = <0x5c 0x4>, <0x128 0x4>;
-					reg-names = "ldb", "lvds";
 					clocks = <&clk IMX8MP_CLK_MEDIA_LDB_ROOT>;
 					clock-names = "ldb";
 					assigned-clocks = <&clk IMX8MP_CLK_MEDIA_LDB>;

-- 
2.47.3

Re: [PATCH 2/4] Revert "dt-bindings: display: bridge: ldb: Fill in reg property"

[Rob Herring (Arm)]

On Mon, 04 May 2026 22:21:42 +0200, Marco Felsch wrote:
> This reverts commit 16c8d76abe83d75b578d72ee22d25a52c764e14a.
> 
> Remove the 'reg' and 'reg-names' property from the LDB.
> 
> The LDB is either part of the IOMUX_GPR (i.MX6SX) or the BLKCTRL
> (i.MX8MP, i.MX93) register space. Both IOMUX_GPR and BLKCTRL are
> register ranges with loose register definitions. E.g.
> 
>   - On the i.MX8MP there is one register which controls the AXI
>     threshold for two different IPs (BIT(31:16) - IP1, BIT(15:0) - IP2).
>   - On the i.MX6SX IOMUXC_GPR5 controlls: CSI2 mux, WDOG3 settings, PXP
>     handshake, ...
> 
> In conclusion: it can't be ensured that one register belongs to one
> dedicated IP and the LDB is rather an exception than the rule.
> 
> Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> ---
>  .../devicetree/bindings/display/bridge/fsl,ldb.yaml       | 15 +--------------
>  1 file changed, 1 insertion(+), 14 deletions(-)
> 

My bot found errors running 'make dt_binding_check' on your patch:

yamllint warnings/errors:

dtschema/dtc warnings/errors:
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/soc/imx/fsl,imx8mp-media-blk-ctrl.example.dtb: blk-ctrl@32ec0000 (fsl,imx8mp-media-blk-ctrl): bridge@5c: 'reg', 'reg-names' do not match any of the regexes: '^pinctrl-[0-9]+$'
	from schema $id: http://devicetree.org/schemas/soc/imx/fsl,imx8mp-media-blk-ctrl.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/soc/imx/fsl,imx8mp-media-blk-ctrl.example.dtb: blk-ctrl@32ec0000 (fsl,imx8mp-media-blk-ctrl): bridge@5c: Unevaluated properties are not allowed ('reg', 'reg-names' were unexpected)
	from schema $id: http://devicetree.org/schemas/soc/imx/fsl,imx8mp-media-blk-ctrl.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/soc/imx/fsl,imx8mp-media-blk-ctrl.example.dtb: bridge@5c (fsl,imx8mp-ldb): 'reg', 'reg-names' do not match any of the regexes: '^pinctrl-[0-9]+$'
	from schema $id: http://devicetree.org/schemas/display/bridge/fsl,ldb.yaml

doc reference errors (make refcheckdocs):

See https://patchwork.kernel.org/project/devicetree/patch/20260504-v7-1-topic-ldb-fixes-v1-2-0125d937ff7f@pengutronix.de

The base for the series is generally the latest rc1. A different dependency
should be noted in *this* patch.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit after running the above command yourself. Note
that DT_SCHEMA_FILES can be set to your schema file to speed up checking
your schema. However, it must be unset to test all examples with your schema.

Re: [PATCH 2/4] Revert "dt-bindings: display: bridge: ldb: Fill in reg property"

[Rob Herring]

On Mon, May 04, 2026 at 10:21:42PM +0200, Marco Felsch wrote:
> This reverts commit 16c8d76abe83d75b578d72ee22d25a52c764e14a.
> 
> Remove the 'reg' and 'reg-names' property from the LDB.
> 
> The LDB is either part of the IOMUX_GPR (i.MX6SX) or the BLKCTRL
> (i.MX8MP, i.MX93) register space. Both IOMUX_GPR and BLKCTRL are
> register ranges with loose register definitions. E.g.
> 
>   - On the i.MX8MP there is one register which controls the AXI
>     threshold for two different IPs (BIT(31:16) - IP1, BIT(15:0) - IP2).
>   - On the i.MX6SX IOMUXC_GPR5 controlls: CSI2 mux, WDOG3 settings, PXP
>     handshake, ...
> 
> In conclusion: it can't be ensured that one register belongs to one
> dedicated IP and the LDB is rather an exception than the rule.

It is fine if there's a child node for LDB if the LDB registers are 
consistent, but the other misc things are represented by the parent 
node. It is certainly not a requirement that either everything be in 
child nodes or nothing be in child nodes.

What I don't see in this series is what problem does this fix? If you 
are going to break compatibility, then there had better be a good 
reason.

Rob

Re: [PATCH 2/4] Revert "dt-bindings: display: bridge: ldb: Fill in reg property"

[Marco Felsch]

On 26-05-05, Rob Herring wrote:
> On Mon, May 04, 2026 at 10:21:42PM +0200, Marco Felsch wrote:
> > This reverts commit 16c8d76abe83d75b578d72ee22d25a52c764e14a.
> > 
> > Remove the 'reg' and 'reg-names' property from the LDB.
> > 
> > The LDB is either part of the IOMUX_GPR (i.MX6SX) or the BLKCTRL
> > (i.MX8MP, i.MX93) register space. Both IOMUX_GPR and BLKCTRL are
> > register ranges with loose register definitions. E.g.
> > 
> >   - On the i.MX8MP there is one register which controls the AXI
> >     threshold for two different IPs (BIT(31:16) - IP1, BIT(15:0) - IP2).
> >   - On the i.MX6SX IOMUXC_GPR5 controlls: CSI2 mux, WDOG3 settings, PXP
> >     handshake, ...
> > 
> > In conclusion: it can't be ensured that one register belongs to one
> > dedicated IP and the LDB is rather an exception than the rule.
> 
> It is fine if there's a child node for LDB if the LDB registers are 
> consistent, but the other misc things are represented by the parent 
> node. It is certainly not a requirement that either everything be in 
> child nodes or nothing be in child nodes.
> 
> What I don't see in this series is what problem does this fix? If you 
> are going to break compatibility, then there had better be a good 
> reason.

Hi Rob,

with the upcoming i.MX9x SoCs the parent syscon (BLKCTRL) controlls
multiple other IPs, e.g. a DPI mux added by commit 3feaa4342637
("dt-bindings: soc: imx93-media-blk-ctrl: Add PDFC subnode to schema and
example").

During the discussion of the above commit we agreed that the sub-devices
of the syscon shall not use the reg property due to the fact that one
register serves multiple purposes. In the above case the same register
controlling the dpi-mux also controlls MIPI-DSI bits. The MIPI-DSI bits
can be abstracted as drm-bridge as well. Two sub-devs using the same
'reg' property below the same parent seems odd and I don't know if this
allowed either.

Now the LDB is also part of this BLKCTRL syscon device but requires the
reg property. TBH, I don't know why the reg property was added in the
first place, due to the above fact (multiple sub-devs - same register).

Of course, we could limit the breakage to i.MX9* SoCs only which is done
by:
 - https://lore.kernel.org/all/20260329-fsl_ldb_schema_fix-v1-1-351372754bc0@nxp.com/

but I don't think that this would be nice from user and from maintainer
perspective, because:
 1) The same LDB "IP" would have a different dt-binding
    (user perspective)
 2) It introduces another dimension drivers need to care about
    (maintainer perspective)

Therefore I went this way to drop it all together to make it easier for
the user and the maintainers.

Regards,
  Marco



> 
> Rob
> 

-- 
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