Hi Sahil,
Am 2022-01-06 07:09, schrieb Sahil Malhotra (OSS):
I don't know I follow. u-boot and linux should have the same device
tree;
regardless if that device is used or not. So applying the overlay just
for linux isn't
enough here.
Ok, I don't think that as of now, in all platforms uboot and linux
have same devie
tree.
That doesn't mean it is ok to diverge again. I put a lot of effort in
syncing uboot's LS1028A device tree with linux.
But I will try to address your concern, but I don’t know how to apply
overlay to
dtb which is embedded in u-boot binary, Can you please point me to one
reference
which is doing this thing, I will take reference from there.
Sorry I can't advise you with that. There is board_fix_fdt() maybe
that will help. But I'm not conviced this is the correct approach,
see below.
> We don't use DTB in OP-TEE, but when we use CAAM in OP-TEE, OP-TEE
> reserves One Job Ring for its use and that is communicated to Kernel
> using DTB overlay.
>
>> what if the overlay doesn't match the dtb?
> I didn't get this point, can you please elaborate a little.
You are merging a dtb fragment with an unknown dtb, right? Who says
they
match? you might have an old dtb where the supplied dtb fragment
doesn't
make any sense.
I might be missing something here. Eg. where is the linux dtb supposed
to come
from? This patchset is really missing an example and a description how
things
should work.
If supplied DTB does not match with DTB overlay fragment. then overlay
will not get applied.
I don't think this is what happens here. fdt_overlay_apply() will
mark the fdt as damaged and there will be no fdt at all.
We don't have any control on where user picks the DTB, but we can only
make sure DTB
overlay feature must work with DTBs which are upstreamed
If user makes its own customized DTB, we cannot make sure that things
will work.
Again. Is there any documentation on how this should all work
together? Where does optee get its device tree from? Shouldn't
it be the same device tree as u-boot and linux? Shouldn't optee
modify the device tree in place before jumping back to u-boot?
Andrey, do you know how this works on imx?
-michael
