Re: [PATCH v8 1/9] dt-bindings: display: fsl,ldb: Add i.MX94 LDB

[Marek Vasut <marex@nabladev.com>]

On 3/20/26 9:23 AM, Marco Felsch wrote:

Hello Marco,

>> The LDB driver was always written with parsing 'reg' out of the DT, so
> 
> Not sure what you mean by always.

By always, I mean since the very beginning.

> I re-checked the imx6qdl.dtsi which
> uses the ipuv3/imx-ldb.c driver. These platforms don't use the 'reg'
> property either.

Which is a different driver, although for a similar IP. We are however 
currently talking about drivers/gpu/drm/bridge/fsl-ldb.c , right ?

>> encoding the register offsets into the driver was a mistake. The LDB
>> controls two registers, which can be comfortably described in DT.
> 
> Sorry but I have to disagree on this. It's no about if it's possible,
> it's about if the abstraction is correct and IMHO the LDB is just one
> subdevice of the syscon. For i.MX6SX the syscon is the iomuxc-gpr for
> the i.MX8M and i.MX9 this is now a blkctrl.

Right, and the "reg" DT property specifies at which offsets are the LDB 
control registers from the start of that blkctrl. What is the problem 
with that ?

Look at e.g. imx8mp.dtsi as an example with blkctrl and LDB as a subnode 
with "reg" DT properties:

1938                         media_blk_ctrl: blk-ctrl@32ec0000 {
1939                                 compatible = 
"fsl,imx8mp-media-blk-ctrl",
1940                                              "syscon";
...
2003                                 lvds_bridge: bridge@5c {
2004                                         compatible = "fsl,imx8mp-ldb";
2005                                         reg = <0x5c 0x4>, <0x128 0x4>;
2006                                         reg-names = "ldb", "lvds";