[PATCH] dt-bindings: display: bridge: ldb: Require reg property only for i.MX6SX/8MP LDBs

[PATCH] dt-bindings: display: bridge: ldb: Require reg property only for i.MX6SX/8MP LDBs

[Liu Ying]

LDB's parent device could be a syscon which doesn't allow a reg property
to be present in it's child devices, e.g., NXP i.MX93 Media blk-ctrl
has a child device NXP i.MX93 Parallel Display Format Configuration(PDFC)
without a reg property(LDB is also a child device of the Media blk-ctrl).
To make the LDB schema be able to describe LDBs without the reg property
like i.MX93 LDB, require the reg property only for i.MX6SX/8MP LDBs.

Fixes: 8aa2f0ac08d3 ("dt-bindings: display: bridge: ldb: Add check for reg and reg-names")
Signed-off-by: Liu Ying <victor.liu@nxp.com>
---
 .../bindings/display/bridge/fsl,ldb.yaml           | 23 ++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
index 7f380879fffd..5f6dc2b11d7b 100644
--- a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
+++ b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
@@ -28,6 +28,7 @@ properties:
     const: ldb
 
   reg:
+    minItems: 1
     maxItems: 2
 
   reg-names:
@@ -68,7 +69,6 @@ required:
   - compatible
   - clocks
   - ports
-  - reg
 
 allOf:
   - if:
@@ -83,12 +83,23 @@ allOf:
         ports:
           properties:
             port@2: false
+
   - if:
-      not:
-        properties:
-          compatible:
-            contains:
-              const: fsl,imx6sx-ldb
+      properties:
+        compatible:
+          contains:
+            enum:
+              - fsl,imx6sx-ldb
+              - fsl,imx8mp-ldb
+    then:
+      required:
+        - reg
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: fsl,imx8mp-ldb
     then:
       required:
         - reg-names

---
base-commit: 3b058d1aeeeff27a7289529c4944291613b364e9
change-id: 20260329-fsl_ldb_schema_fix-4fe01c42bff3

Best regards,
-- 
Liu Ying <victor.liu@nxp.com>

Re: [PATCH] dt-bindings: display: bridge: ldb: Require reg property only for i.MX6SX/8MP LDBs

[Marco Felsch]

Hi Liu,

sorry for not writting back earlier, the last weeks were quite busy.

On 26-03-29, Liu Ying wrote:
> LDB's parent device could be a syscon which doesn't allow a reg property
> to be present in it's child devices, e.g., NXP i.MX93 Media blk-ctrl
> has a child device NXP i.MX93 Parallel Display Format Configuration(PDFC)
> without a reg property(LDB is also a child device of the Media blk-ctrl).
> To make the LDB schema be able to describe LDBs without the reg property
> like i.MX93 LDB, require the reg property only for i.MX6SX/8MP LDBs.

NACK, we want to describe the HW and from HW PoV the LDB is and was
always part of a syscon. This is the case for all SoCs i.MX6SX/8MP/93.

> Fixes: 8aa2f0ac08d3 ("dt-bindings: display: bridge: ldb: Add check for reg and reg-names")

Therefore I would just revert this patch completely.

Regards,
  Marco

> Signed-off-by: Liu Ying <victor.liu@nxp.com>
> ---
>  .../bindings/display/bridge/fsl,ldb.yaml           | 23 ++++++++++++++++------
>  1 file changed, 17 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
> index 7f380879fffd..5f6dc2b11d7b 100644
> --- a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
> +++ b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
> @@ -28,6 +28,7 @@ properties:
>      const: ldb
>  
>    reg:
> +    minItems: 1
>      maxItems: 2
>  
>    reg-names:
> @@ -68,7 +69,6 @@ required:
>    - compatible
>    - clocks
>    - ports
> -  - reg
>  
>  allOf:
>    - if:
> @@ -83,12 +83,23 @@ allOf:
>          ports:
>            properties:
>              port@2: false
> +
>    - if:
> -      not:
> -        properties:
> -          compatible:
> -            contains:
> -              const: fsl,imx6sx-ldb
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - fsl,imx6sx-ldb
> +              - fsl,imx8mp-ldb
> +    then:
> +      required:
> +        - reg
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: fsl,imx8mp-ldb
>      then:
>        required:
>          - reg-names
> 
> ---
> base-commit: 3b058d1aeeeff27a7289529c4944291613b364e9
> change-id: 20260329-fsl_ldb_schema_fix-4fe01c42bff3
> 
> Best regards,
> -- 
> Liu Ying <victor.liu@nxp.com>
> 
> 

-- 
#gernperDu 
#CallMeByMyFirstName

Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | https://www.pengutronix.de/ |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-9    |

Re: [PATCH] dt-bindings: display: bridge: ldb: Require reg property only for i.MX6SX/8MP LDBs

[Marek Vasut]

On 3/29/26 7:42 PM, Marco Felsch wrote:

Hello Marco,

> sorry for not writting back earlier, the last weeks were quite busy.

Tell me about it ...

> On 26-03-29, Liu Ying wrote:
>> LDB's parent device could be a syscon which doesn't allow a reg property
>> to be present in it's child devices, e.g., NXP i.MX93 Media blk-ctrl
>> has a child device NXP i.MX93 Parallel Display Format Configuration(PDFC)
>> without a reg property(LDB is also a child device of the Media blk-ctrl).
>> To make the LDB schema be able to describe LDBs without the reg property
>> like i.MX93 LDB, require the reg property only for i.MX6SX/8MP LDBs.
> 
> NACK, we want to describe the HW and from HW PoV the LDB is and was
> always part of a syscon. This is the case for all SoCs i.MX6SX/8MP/93.
> 
>> Fixes: 8aa2f0ac08d3 ("dt-bindings: display: bridge: ldb: Add check for reg and reg-names")
> 
> Therefore I would just revert this patch completely.
Last time, I pointed out the hardware is part of syscon, but as a 
subnode and therefore with reg properties. What is the problem there ?

Re: [PATCH] dt-bindings: display: bridge: ldb: Require reg property only for i.MX6SX/8MP LDBs

[Marco Felsch]

Hi Marek,

On 26-03-29, Marek Vasut wrote:
> On 3/29/26 7:42 PM, Marco Felsch wrote:
> 
> Hello Marco,
> 
> > sorry for not writting back earlier, the last weeks were quite busy.
> 
> Tell me about it ...

^^

> > On 26-03-29, Liu Ying wrote:
> > > LDB's parent device could be a syscon which doesn't allow a reg property
> > > to be present in it's child devices, e.g., NXP i.MX93 Media blk-ctrl
> > > has a child device NXP i.MX93 Parallel Display Format Configuration(PDFC)
> > > without a reg property(LDB is also a child device of the Media blk-ctrl).
> > > To make the LDB schema be able to describe LDBs without the reg property
> > > like i.MX93 LDB, require the reg property only for i.MX6SX/8MP LDBs.
> > 
> > NACK, we want to describe the HW and from HW PoV the LDB is and was
> > always part of a syscon. This is the case for all SoCs i.MX6SX/8MP/93.
> > 
> > > Fixes: 8aa2f0ac08d3 ("dt-bindings: display: bridge: ldb: Add check for reg and reg-names")
> > 
> > Therefore I would just revert this patch completely.
> Last time, I pointed out the hardware is part of syscon, but as a subnode
> and therefore with reg properties. What is the problem there ?

To quote the DT spec here:

"""
The reg property describes the address of the device’s resources within
the address space defined by its parent bus.
"""

The parent bus is not the parent iomuxc (i.MX6X) nor the blk-ctrl
(i.MX8MP/93) device. Therefore this is wrong IMHO and should be dropped.

There will be no regression from driver POV since your patchset which
would add the support to parse the reg is not merged yet.

Regards,
  Marco

-- 
#gernperDu 
#CallMeByMyFirstName

Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | https://www.pengutronix.de/ |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-9    |

Re: [PATCH] dt-bindings: display: bridge: ldb: Require reg property only for i.MX6SX/8MP LDBs

[Marek Vasut]

On 3/30/26 8:29 AM, Marco Felsch wrote:

Hello Marco,

>>> On 26-03-29, Liu Ying wrote:
>>>> LDB's parent device could be a syscon which doesn't allow a reg property
>>>> to be present in it's child devices, e.g., NXP i.MX93 Media blk-ctrl
>>>> has a child device NXP i.MX93 Parallel Display Format Configuration(PDFC)
>>>> without a reg property(LDB is also a child device of the Media blk-ctrl).
>>>> To make the LDB schema be able to describe LDBs without the reg property
>>>> like i.MX93 LDB, require the reg property only for i.MX6SX/8MP LDBs.
>>>
>>> NACK, we want to describe the HW and from HW PoV the LDB is and was
>>> always part of a syscon. This is the case for all SoCs i.MX6SX/8MP/93.
>>>
>>>> Fixes: 8aa2f0ac08d3 ("dt-bindings: display: bridge: ldb: Add check for reg and reg-names")
>>>
>>> Therefore I would just revert this patch completely.
>> Last time, I pointed out the hardware is part of syscon, but as a subnode
>> and therefore with reg properties. What is the problem there ?
> 
> To quote the DT spec here:
> 
> """
> The reg property describes the address of the device’s resources within
> the address space defined by its parent bus.
> """

That parent bus would be the syscon, wouldn't it.

> The parent bus is not the parent iomuxc (i.MX6X) nor the blk-ctrl
> (i.MX8MP/93) device. Therefore this is wrong IMHO and should be dropped.

How so ? What is the parent bus ?

Re: [PATCH] dt-bindings: display: bridge: ldb: Require reg property only for i.MX6SX/8MP LDBs

[Laurentiu Palcu]

Hi Marco, Marek, Ying,

On Tue, Mar 31, 2026 at 01:22:19AM +0200, Marek Vasut wrote:
> On 3/30/26 8:29 AM, Marco Felsch wrote:
> 
> Hello Marco,
> 
> > > > On 26-03-29, Liu Ying wrote:
> > > > > LDB's parent device could be a syscon which doesn't allow a reg property
> > > > > to be present in it's child devices, e.g., NXP i.MX93 Media blk-ctrl
> > > > > has a child device NXP i.MX93 Parallel Display Format Configuration(PDFC)
> > > > > without a reg property(LDB is also a child device of the Media blk-ctrl).
> > > > > To make the LDB schema be able to describe LDBs without the reg property
> > > > > like i.MX93 LDB, require the reg property only for i.MX6SX/8MP LDBs.
> > > > 
> > > > NACK, we want to describe the HW and from HW PoV the LDB is and was
> > > > always part of a syscon. This is the case for all SoCs i.MX6SX/8MP/93.
> > > > 
> > > > > Fixes: 8aa2f0ac08d3 ("dt-bindings: display: bridge: ldb: Add check for reg and reg-names")
> > > > 
> > > > Therefore I would just revert this patch completely.
> > > Last time, I pointed out the hardware is part of syscon, but as a subnode
> > > and therefore with reg properties. What is the problem there ?
> > 
> > To quote the DT spec here:
> > 
> > """
> > The reg property describes the address of the device’s resources within
> > the address space defined by its parent bus.
> > """
> 
> That parent bus would be the syscon, wouldn't it.
> 
> > The parent bus is not the parent iomuxc (i.MX6X) nor the blk-ctrl
> > (i.MX8MP/93) device. Therefore this is wrong IMHO and should be dropped.
> 
> How so ? What is the parent bus ?

It looks like the discussion is stuck on 2 things:

1. DT spec argument hasn't been fully addressed: Marek asked "what is
   the parent bus if not the syscon?". That question is still open. Syscon
   children carrying 'reg' to express their offset within the parent's MMIO
   range is a common upstream pattern. Marco, can you explain why syscon
   doesn't qualify as the address space provider here?

2. Regardless of (1), removing 'reg' from the imx6sx/imx8mp DT nodes is
   an ABI break, those nodes are already upstream. Ying's patch is
   the minimal fix that respects that constraint while unblocking imx93.

Marco, a broader cleanup of 'reg' from imx6sx/imx8mp would need to be a
separate patch with an explicit plan for the ABI impact... So, for now, my
suggestion is to move forward with Ying's solution.

-- 
Thanks,
Laurentiu

Re: [PATCH] dt-bindings: display: bridge: ldb: Require reg property only for i.MX6SX/8MP LDBs

[Liu Ying]

On Thu, Apr 16, 2026 at 01:20:20PM +0300, Laurentiu Palcu wrote:
> Hi Marco, Marek, Ying,
> 
> On Tue, Mar 31, 2026 at 01:22:19AM +0200, Marek Vasut wrote:
> > On 3/30/26 8:29 AM, Marco Felsch wrote:
> > 
> > Hello Marco,
> > 
> > > > > On 26-03-29, Liu Ying wrote:
> > > > > > LDB's parent device could be a syscon which doesn't allow a reg property
> > > > > > to be present in it's child devices, e.g., NXP i.MX93 Media blk-ctrl
> > > > > > has a child device NXP i.MX93 Parallel Display Format Configuration(PDFC)
> > > > > > without a reg property(LDB is also a child device of the Media blk-ctrl).
> > > > > > To make the LDB schema be able to describe LDBs without the reg property
> > > > > > like i.MX93 LDB, require the reg property only for i.MX6SX/8MP LDBs.
> > > > > 
> > > > > NACK, we want to describe the HW and from HW PoV the LDB is and was
> > > > > always part of a syscon. This is the case for all SoCs i.MX6SX/8MP/93.
> > > > > 
> > > > > > Fixes: 8aa2f0ac08d3 ("dt-bindings: display: bridge: ldb: Add check for reg and reg-names")
> > > > > 
> > > > > Therefore I would just revert this patch completely.
> > > > Last time, I pointed out the hardware is part of syscon, but as a subnode
> > > > and therefore with reg properties. What is the problem there ?
> > > 
> > > To quote the DT spec here:
> > > 
> > > """
> > > The reg property describes the address of the device’s resources within
> > > the address space defined by its parent bus.
> > > """
> > 
> > That parent bus would be the syscon, wouldn't it.
> > 
> > > The parent bus is not the parent iomuxc (i.MX6X) nor the blk-ctrl
> > > (i.MX8MP/93) device. Therefore this is wrong IMHO and should be dropped.
> > 
> > How so ? What is the parent bus ?
> 
> It looks like the discussion is stuck on 2 things:
> 
> 1. DT spec argument hasn't been fully addressed: Marek asked "what is
>    the parent bus if not the syscon?". That question is still open. Syscon
>    children carrying 'reg' to express their offset within the parent's MMIO
>    range is a common upstream pattern. Marco, can you explain why syscon
>    doesn't qualify as the address space provider here?
> 
> 2. Regardless of (1), removing 'reg' from the imx6sx/imx8mp DT nodes is
>    an ABI break, those nodes are already upstream. Ying's patch is
>    the minimal fix that respects that constraint while unblocking imx93.

Yes, I don't want to break ABI by removing the 'reg' property from i.MX6SX
and i.MX8MP LDB DT nodes.  And, I don't see a way to remove it, which
doesn't break ABI.

Laurentiu, Marek, can you please provide your A-b or R-b tags if you are
fine with my patch?  I see your positive opinion on the idea of this
patch, based on previous discussion[1][2].

[1] https://lore.kernel.org/all/p7glzm344tiu76zm5aa7qq4lswdcjuqlqel3hl3tr3s2cllltj@i2eyzuux4cj3/
[2] https://lore.kernel.org/all/a4a5284d-6004-46c5-b5a3-f8eb4d9b3680@nabladev.com/

> 
> Marco, a broader cleanup of 'reg' from imx6sx/imx8mp would need to be a
> separate patch with an explicit plan for the ABI impact... So, for now, my
> suggestion is to move forward with Ying's solution.

I'm open to any better idea than my patch to support i.MX93 LDB in DT.
If there is any, I'd like to see plan/discussion/patch for that.

> 
> -- 
> Thanks,
> Laurentiu

-- 
Regards,
Liu Ying

Re: [PATCH] dt-bindings: display: bridge: ldb: Require reg property only for i.MX6SX/8MP LDBs

[Liu Ying]

On Sun, Mar 29, 2026 at 07:42:23PM +0200, Marco Felsch wrote:
> Hi Liu,

Hi Marco,

> 
> sorry for not writting back earlier, the last weeks were quite busy.
> 
> On 26-03-29, Liu Ying wrote:
>> LDB's parent device could be a syscon which doesn't allow a reg property
>> to be present in it's child devices, e.g., NXP i.MX93 Media blk-ctrl
>> has a child device NXP i.MX93 Parallel Display Format Configuration(PDFC)
>> without a reg property(LDB is also a child device of the Media blk-ctrl).
>> To make the LDB schema be able to describe LDBs without the reg property
>> like i.MX93 LDB, require the reg property only for i.MX6SX/8MP LDBs.
> 
> NACK, we want to describe the HW and from HW PoV the LDB is and was
> always part of a syscon. This is the case for all SoCs i.MX6SX/8MP/93.

The reality is that i.MX6SX and i.MX8MP LDB DT nodes are already in-tree.
People may take them as ABI(not only for Linux, but also for other
potential projects which use the LDB schema and/or the DT nodes).

> 
>> Fixes: 8aa2f0ac08d3 ("dt-bindings: display: bridge: ldb: Add check for reg and reg-names")
> 
> Therefore I would just revert this patch completely.

IMHO, it doesn't make too much difference between my patch and reverting
this offending patch, because of the ABI, i.e., the reg properties in
i.MX6SX and i.MX8MP LDB DT nodes are supposed to be stable.

I feel that what you are asking for is even more than simply reverting
this offending patch, that is to say, completely disallowing the reg and
reg-names properties for LDBs across all SoCs.  But again, that would
break the ABI.

> 
> Regards,
>   Marco
> 
>> Signed-off-by: Liu Ying <victor.liu@nxp.com>
>> ---
>>  .../bindings/display/bridge/fsl,ldb.yaml           | 23 ++++++++++++++++------
>>  1 file changed, 17 insertions(+), 6 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
>> index 7f380879fffd..5f6dc2b11d7b 100644
>> --- a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
>> +++ b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
>> @@ -28,6 +28,7 @@ properties:
>>      const: ldb
>>  
>>    reg:
>> +    minItems: 1
>>      maxItems: 2
>>  
>>    reg-names:
>> @@ -68,7 +69,6 @@ required:
>>    - compatible
>>    - clocks
>>    - ports
>> -  - reg
>>  
>>  allOf:
>>    - if:
>> @@ -83,12 +83,23 @@ allOf:
>>          ports:
>>            properties:
>>              port@2: false
>> +
>>    - if:
>> -      not:
>> -        properties:
>> -          compatible:
>> -            contains:
>> -              const: fsl,imx6sx-ldb
>> +      properties:
>> +        compatible:
>> +          contains:
>> +            enum:
>> +              - fsl,imx6sx-ldb
>> +              - fsl,imx8mp-ldb
>> +    then:
>> +      required:
>> +        - reg
>> +
>> +  - if:
>> +      properties:
>> +        compatible:
>> +          contains:
>> +            const: fsl,imx8mp-ldb
>>      then:
>>        required:
>>          - reg-names
>>
>> ---
>> base-commit: 3b058d1aeeeff27a7289529c4944291613b364e9
>> change-id: 20260329-fsl_ldb_schema_fix-4fe01c42bff3
>>
>> Best regards,
>> -- 
>> Liu Ying <victor.liu@nxp.com>
>>
>>
> 

-- 
Regards,
Liu Ying

Re: [PATCH] dt-bindings: display: bridge: ldb: Require reg property only for i.MX6SX/8MP LDBs

[Marco Felsch]

On 26-03-30, Liu Ying wrote:
> On Sun, Mar 29, 2026 at 07:42:23PM +0200, Marco Felsch wrote:
> > Hi Liu,
> 
> Hi Marco,
> 
> > 
> > sorry for not writting back earlier, the last weeks were quite busy.
> > 
> > On 26-03-29, Liu Ying wrote:
> >> LDB's parent device could be a syscon which doesn't allow a reg property
> >> to be present in it's child devices, e.g., NXP i.MX93 Media blk-ctrl
> >> has a child device NXP i.MX93 Parallel Display Format Configuration(PDFC)
> >> without a reg property(LDB is also a child device of the Media blk-ctrl).
> >> To make the LDB schema be able to describe LDBs without the reg property
> >> like i.MX93 LDB, require the reg property only for i.MX6SX/8MP LDBs.
> > 
> > NACK, we want to describe the HW and from HW PoV the LDB is and was
> > always part of a syscon. This is the case for all SoCs i.MX6SX/8MP/93.
> 
> The reality is that i.MX6SX and i.MX8MP LDB DT nodes are already in-tree.

What do you mean by 'already in-tee'?

> People may take them as ABI(not only for Linux, but also for other
> potential projects which use the LDB schema and/or the DT nodes).

Not sure about this. The DT sould be backward compatible, meaning an old
DT shouldn't break new users e.g. old DT with 'reg' property present
shouldn't break new u-boot/barebox/linux/... drivers. But a new DT could
fix/change the behavior for new u-boot/barebox/linux/... drivers.

So no, I don't see a problem here.

> >> Fixes: 8aa2f0ac08d3 ("dt-bindings: display: bridge: ldb: Add check for reg and reg-names")
> > 
> > Therefore I would just revert this patch completely.
> 
> IMHO, it doesn't make too much difference between my patch and reverting
> this offending patch, because of the ABI, i.e., the reg properties in
> i.MX6SX and i.MX8MP LDB DT nodes are supposed to be stable.

Please see above. If that would be the case, your DT must be rock-solid
bug-free from day one, which is highly unlikely.

> I feel that what you are asking for is even more than simply reverting
> this offending patch, that is to say, completely disallowing the reg and
> reg-names properties for LDBs across all SoCs.  But again, that would
> break the ABI.

Please see above. IMHO it's more confusing if the same "IP" requires the
'reg' for i.MX6SX/8MP but doesn't require it for the i.MX93. Therefore I
would like to keep it consistent.

Regards,
  Marco

> 
> > 
> > Regards,
> >   Marco
> > 
> >> Signed-off-by: Liu Ying <victor.liu@nxp.com>
> >> ---
> >>  .../bindings/display/bridge/fsl,ldb.yaml           | 23 ++++++++++++++++------
> >>  1 file changed, 17 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
> >> index 7f380879fffd..5f6dc2b11d7b 100644
> >> --- a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
> >> +++ b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
> >> @@ -28,6 +28,7 @@ properties:
> >>      const: ldb
> >>  
> >>    reg:
> >> +    minItems: 1
> >>      maxItems: 2
> >>  
> >>    reg-names:
> >> @@ -68,7 +69,6 @@ required:
> >>    - compatible
> >>    - clocks
> >>    - ports
> >> -  - reg
> >>  
> >>  allOf:
> >>    - if:
> >> @@ -83,12 +83,23 @@ allOf:
> >>          ports:
> >>            properties:
> >>              port@2: false
> >> +
> >>    - if:
> >> -      not:
> >> -        properties:
> >> -          compatible:
> >> -            contains:
> >> -              const: fsl,imx6sx-ldb
> >> +      properties:
> >> +        compatible:
> >> +          contains:
> >> +            enum:
> >> +              - fsl,imx6sx-ldb
> >> +              - fsl,imx8mp-ldb
> >> +    then:
> >> +      required:
> >> +        - reg
> >> +
> >> +  - if:
> >> +      properties:
> >> +        compatible:
> >> +          contains:
> >> +            const: fsl,imx8mp-ldb
> >>      then:
> >>        required:
> >>          - reg-names
> >>
> >> ---
> >> base-commit: 3b058d1aeeeff27a7289529c4944291613b364e9
> >> change-id: 20260329-fsl_ldb_schema_fix-4fe01c42bff3
> >>
> >> Best regards,
> >> -- 
> >> Liu Ying <victor.liu@nxp.com>
> >>
> >>
> > 
> 
> -- 
> Regards,
> Liu Ying
> 

-- 
#gernperDu 
#CallMeByMyFirstName

Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | https://www.pengutronix.de/ |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-9    |

Re: [PATCH] dt-bindings: display: bridge: ldb: Require reg property only for i.MX6SX/8MP LDBs

[Liu Ying]

Hi Marco,

On Mon, Mar 30, 2026 at 12:28:00PM +0200, Marco Felsch wrote:
> On 26-03-30, Liu Ying wrote:
>> On Sun, Mar 29, 2026 at 07:42:23PM +0200, Marco Felsch wrote:
>>> Hi Liu,
>>
>> Hi Marco,
>>
>>>
>>> sorry for not writting back earlier, the last weeks were quite busy.
>>>
>>> On 26-03-29, Liu Ying wrote:
>>>> LDB's parent device could be a syscon which doesn't allow a reg property
>>>> to be present in it's child devices, e.g., NXP i.MX93 Media blk-ctrl
>>>> has a child device NXP i.MX93 Parallel Display Format Configuration(PDFC)
>>>> without a reg property(LDB is also a child device of the Media blk-ctrl).
>>>> To make the LDB schema be able to describe LDBs without the reg property
>>>> like i.MX93 LDB, require the reg property only for i.MX6SX/8MP LDBs.
>>>
>>> NACK, we want to describe the HW and from HW PoV the LDB is and was
>>> always part of a syscon. This is the case for all SoCs i.MX6SX/8MP/93.
>>
>> The reality is that i.MX6SX and i.MX8MP LDB DT nodes are already in-tree.
> 
> What do you mean by 'already in-tee'?

I mean the LDB DT nodes are already present in device trees.

You may find the LDB DT nodes with the below command line.
git grep -A5 lvds_bridge arch/ | grep -E '6sx|8mp'

> 
>> People may take them as ABI(not only for Linux, but also for other
>> potential projects which use the LDB schema and/or the DT nodes).
> 
> Not sure about this. The DT sould be backward compatible, meaning an old
> DT shouldn't break new users e.g. old DT with 'reg' property present
> shouldn't break new u-boot/barebox/linux/... drivers. But a new DT could
> fix/change the behavior for new u-boot/barebox/linux/... drivers.
> 
> So no, I don't see a problem here.

An OS could try to get the LDB register(s) via the reg and reg-names
property which are currently present in i.MX6SX and i.MX8MP LDB DT nodes.
If we remove the properties from the DT nodes, then that OS would be broken.
That's the ABI breakage problem I talked about.

> 
>>>> Fixes: 8aa2f0ac08d3 ("dt-bindings: display: bridge: ldb: Add check for reg and reg-names")
>>>
>>> Therefore I would just revert this patch completely.
>>
>> IMHO, it doesn't make too much difference between my patch and reverting
>> this offending patch, because of the ABI, i.e., the reg properties in
>> i.MX6SX and i.MX8MP LDB DT nodes are supposed to be stable.
> 
> Please see above. If that would be the case, your DT must be rock-solid
> bug-free from day one, which is highly unlikely.
> 
>> I feel that what you are asking for is even more than simply reverting
>> this offending patch, that is to say, completely disallowing the reg and
>> reg-names properties for LDBs across all SoCs.  But again, that would
>> break the ABI.
> 
> Please see above. IMHO it's more confusing if the same "IP" requires the
> 'reg' for i.MX6SX/8MP but doesn't require it for the i.MX93. Therefore I
> would like to keep it consistent.

I agree that it's ideal to keep it consistent, however, in order to avoid
the fore-mentioned ABI breakage problem, we have to keep the reg property
being present in i.MX6SX and i.MX8MP LDB DT nodes.

> 
> Regards,
>   Marco
> 
>>
>>>
>>> Regards,
>>>   Marco
>>>
>>>> Signed-off-by: Liu Ying <victor.liu@nxp.com>
>>>> ---
>>>>  .../bindings/display/bridge/fsl,ldb.yaml           | 23 ++++++++++++++++------
>>>>  1 file changed, 17 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
>>>> index 7f380879fffd..5f6dc2b11d7b 100644
>>>> --- a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
>>>> +++ b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
>>>> @@ -28,6 +28,7 @@ properties:
>>>>      const: ldb
>>>>  
>>>>    reg:
>>>> +    minItems: 1
>>>>      maxItems: 2
>>>>  
>>>>    reg-names:
>>>> @@ -68,7 +69,6 @@ required:
>>>>    - compatible
>>>>    - clocks
>>>>    - ports
>>>> -  - reg
>>>>  
>>>>  allOf:
>>>>    - if:
>>>> @@ -83,12 +83,23 @@ allOf:
>>>>          ports:
>>>>            properties:
>>>>              port@2: false
>>>> +
>>>>    - if:
>>>> -      not:
>>>> -        properties:
>>>> -          compatible:
>>>> -            contains:
>>>> -              const: fsl,imx6sx-ldb
>>>> +      properties:
>>>> +        compatible:
>>>> +          contains:
>>>> +            enum:
>>>> +              - fsl,imx6sx-ldb
>>>> +              - fsl,imx8mp-ldb
>>>> +    then:
>>>> +      required:
>>>> +        - reg
>>>> +
>>>> +  - if:
>>>> +      properties:
>>>> +        compatible:
>>>> +          contains:
>>>> +            const: fsl,imx8mp-ldb
>>>>      then:
>>>>        required:
>>>>          - reg-names
>>>>
>>>> ---
>>>> base-commit: 3b058d1aeeeff27a7289529c4944291613b364e9
>>>> change-id: 20260329-fsl_ldb_schema_fix-4fe01c42bff3
>>>>
>>>> Best regards,
>>>> -- 
>>>> Liu Ying <victor.liu@nxp.com>
>>>>
>>>>
>>>
>>
>> -- 
>> Regards,
>> Liu Ying
>>
> 

-- 
Regards,
Liu Ying