Hi Robert,
Comments below.
On Mon, Dec 28, 2020 at 7:49 PM Robert Delien via OP-TEE op-tee@lists.trustedfirmware.org wrote:
Hi,
As discussed earlier, our application requires secured display contents and is using a secure frame buffer.
Now to transit from U-Boot to Op-tee as smoothly as possible, I would like to copy the contents from the U-Boot frame buffer into the Optee frame buffer upon LCD driver initialisation.
The U-Boot frame buffer address is calculated at run time and I haven't found a hand-off mechanism, but the physical address can be easily read from the LCDIF peripheral's registers. Unfortunately, no MMU mapping is present per default for this physical address outside the TZDRAM area.
Is it possible to temporarily map this rather arbitrary non-secure physical DDR address outside TZDRAM, so I can access it through a virtual address? Preferably in a way that I can also remove this mapping after copying the frame buffer?
Yes, it's actually easier than one might first imagine. I assume you will interact with OP-TEE via a Pseudo TA. This framebuffer is normal non-secure DDR from OP-TEE point of view, so it should be possible to just supply it as a memref parameter when invoking the PTA.
Cheers, Jens