Re: [PATCH v4 3/4] ARM: dts: imx6ull-colibri: Set LCDIF bus-width

[Luca Ceresoli]

Hi Francesco,

On Wed Sep 16, 2026 at 11:22 AM CEST, Francesco Dolcini wrote:
> Hi Luca,
> thanks for the review.
>
> On Wed, Sep 16, 2026 at 10:42:13AM +0200, Luca Ceresoli wrote:
>> > The lcd DPI interface on colibri imx6ull uses a 18-bit width bus, set
>> > the bus-width property accordingly.
>> >
>> > Signed-off-by: Francesco Dolcini <francesco.dolcini@xxxxxxxxxxx>
>> >
>> > diff --git a/arch/arm/boot/dts/nxp/imx/imx6ull-colibri.dtsi b/arch/arm/boot/dts/nxp/imx/imx6ull-colibri.dtsi
>> > index ec3c1e7301f4..1eb1cf2d7395 100644
>> > --- a/arch/arm/boot/dts/nxp/imx/imx6ull-colibri.dtsi
>> > +++ b/arch/arm/boot/dts/nxp/imx/imx6ull-colibri.dtsi
>> > @@ -229,6 +229,7 @@ &lcdif {
>> >
>> >  	port {
>> >  		lcdif_out: endpoint {
>> > +			bus-width = <18>;
>>
>> I don't know the hardware in detail, but the datasheet [0] mentions 16, 18
>> and 24 bits, and says "Up to 24-bit color (18-bit recommended)". More
>> details in ection 5.6.1.
>>
>> This patch would force 18 bits, but "recommended" suggests 24 bits makes
>> sense in some cases, no?
>>
>> Can you elaborate on this?
>
> The colibri family standard defines only 18-bit for the parallel RGB
> interface on the edge connector, the additional 6-bit are mapped on
> different pins that are not on fixed position, depend on the actual SoM
> and can also be not present at all. The standard/generic colibri family
> carrier boards can only rely on the 18-bits being available therefore.
>
> 24-bit is possible and makes sense only on a specific combo
> carrier+module, and not as a generic SoM feature. Assuming you would
> have such combo you should just override the property on the carrier
> board dts file deviating from the standard colibri family.

Ah, that's clear now, thanks!

> let me know if you want such detailed explanation in the commit message

Yes please. With that added you can add:
+Reviewed-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx>

Same for patch 4.

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com