Mapping an arbitrary SDRAM block outside TZDRAM

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?

Thanks in advance; Your help is highly appreciated.

With kind regards,

Robert.