[U-Boot] P2020 SPL L2 clearing

[Fabian Cenedese]

>>> I'm creating a SPL u-boot image for our board. In the file
>>> arch/powerpc/cpu/mpc85xx/cpu_init_nand.c is the setup for
>>> the L2 cache as SRAM. In the end is a loop that fills the
>>> cache with 0 (512KB in this case).
>>> 
>>> 1. Why is the access byte-wise and not dword-wise? This
>>> is only for mpc85xx and I think they all can access the cache
>>> with 32bits instead of just 8. That would speed up by factor 4
>>> (confirmed in my tests with P2020).
>
>No real reason, probably historic and no one noticed.  Patch welcome to change this to 32-bit accesses, not really sure why we just dont call memset.

I can try that too and see how it goes. I will test this for my board
and send a patch once I get my way around git (didn't use it so far).

>>> 2. Why does the cache to be cleared at all? L2-SRAM is usually
>>> just used to copy in the second part of the u-boot image, so
>>> the 0s will be overwritten again anyway.
>
>This needs to be done because we enable ECC.

Isn't this an optional feature? Shouldn't this loop be enclosed in
# ifdef CONFIG_DDR_ECC or doesn't this apply to L2-SRAM?

Thanks

bye  Fabi