Re: [PATCH 1/2] fsl-layerscape: add dtb overlay feature

[Michael Walle <michael@walle.cc>]

Hi Sahil,

Am 2021-11-17 19:11, schrieb Sahil Malhotra (OSS):
>> Could you please add some description what this is doing and for what
>> this is intended? To have a "DTB overlay feature", it is enough to 
>> just
>> enable CONFIG_OF_LIBFDT_OVERLAY.
> I will add some description, and yes for DTB overlay feature, it is
> enough to enable CONFIG_OF_LIBFDT_OVERLAY but we need to do this step
> before booting the kernel that's why also have to enable
> CONFIG_OF_SYSTEM_SETUP.

Ok. What will the overlay do? Could you give an example?

>> Apparently you're adding an overlay passed by optee. Doesn't this
>> have to be applied to u-boot's control dtb too?
> Yes, we will be applying the overlay passed by optee, yes it will be
> applied to dtb which will be passed to uboot for kernel booting.

If I read this patch correctly, you're modifying the DT before you
jump to linux. But I was asking whether you also have to modify
the DT which is used by u-boot. Eg. if you disable some kind of
crypto nodes (because optee will use them in secure world), this
also have to communicated to u-boot, not only linux, no?

But until you've explained what this is about, this is only
guesswork.

-michael