[Skiboot] [PATCH 14/15] libstb/drivers: Add ROM code driver

Oliver O'Halloran oohall at gmail.com
Sat Sep 3 13:38:04 AEST 2016

On Thu, Aug 11, 2016 at 3:23 PM, Claudio Carvalho
<cclaudio at linux.vnet.ibm.com> wrote:
> +       /**
> +        * We use memcpy_ci to copy the verification code from the secure ROM
> +        * to memory. Due to performance issues we opted to run it from memory.
> +        */
> +       chip = next_chip(NULL);
> +       xscom_read(chip->id, reg_addr, &reg_data);
> +        memcpy_ci(romcode_base_addr, (void*) reg_data,
> +                 ROMCODE_MEMORY_SIZE);

Could you document why accessing the ROM needs to be done with CI
loads? We use them when dealing with MMIO registers (like the XSCOMs)
to ensure loads and stores go to/from the actual register rather than
the cache, but I don't see why this is necessary for a ROM.

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