imx8m optee load address?

[Peng Fan]

On 6/16/2023 9:56 AM, Tim Harvey wrote:
> Greetings,
> 
> I've seen several IMX8M boards include a firmware/optee node in the
> U-Boot dt (git grep optee arch/arm/dts/imx8m*.dtsi) yet but none that
> I see configure binman to actually add the binary in the u-boot.dtsi,
> do anything to keep U-Boot from accessing the OPTEE memory, or
> document how to configure and build OPTEE for imx8m. I would like to
> add such support but I find it odd that OPTEE needs to be built
> differently depending on the dram size.
> 
> Prior to switching to binman (v2021.10)
> arch/arm/mach-imx/mkimage_fit_atf.sh [1] would include tee.bin in the
> FIT image if it was found in the current directory and it was expected
> that you provide a proper TEE_LOAD_ADDR via the env (commit
> a9eed6e1b8d8 ("imx: imx8m: introduce script to generate fit image").
> 
> According to the IMX OPTEE documentation [2] the size and location of
> OPTEE is hard coded (CFG_TZDRAM_START and CFG_TZDRAM_SIZE) but looking
> at the imx-optee source [3] this is calculated based off of
> CFG_DDR_SIZE (which you can provide via env at build time or just
> provide CFG_TZDRAM_START and CFG_TZDRAM_SIZE via env directly).

optee does not support PIE, it could only run at the address that built
time defined.

And the TZASC needs following it to protect the region properly.

> 
> This results in the OPTEE location of 0x7e000000 for 1GiB systems,
> 0xbe000000 for 2GiB systems, and 0x13e000000 for 4GiB systems for
> example. This dependence on dram size causes a couple of issues:
>   - OPTEE location depends on build-time configuration and several
> boards have run-time identification of their memory size
>   - for 4GiB systems the address 0x13e000000 crosses the 32bit address
> boundary and U-Boot hangs

imx optee seems has this. But for overlapping with U-Boot, I doubt that.

> 
> Is there any reason OPTEE can't be located wherever you want and not
> depend on dram size? 

You could , just modify the imx *.mk file per my recall.

I've tried to set it to 0x7e000000 (for a 1GiB
> board) on a 4GiB board and U-Boot hangs near the DRAM banner which is
> likely due to get_ram_size() stepping on OPTEE's memory range but then

You may give a try to disable TZASC settings in OP-TEE first.
And you also need to carve out the memory of OP-TEE from U-Boot MMU
to avoid prefetch.

> I'm not clear why that doesn't occur when OPTEE is located at the top
> of dram on a 1GiB and 2GiB system. How would I go about adding a
> carevout for this?

Are u using upstream optee or NXP downstream optee release?

Regards,
Peng.

> 
> Best Regards,
> 
> Tim
> [1] https://elixir.bootlin.com/u-boot/v2021.10/source/arch/arm/mach-imx/mkimage_fit_atf.sh
> [2] https://www.nxp.com/docs/en/user-guide/IMX_PORTING_GUIDE.pdf
> [3] https://github.com/nxp-imx/imx-optee-os