On Tue, Jan 17, 2012 at 8:47 PM, Russell King - ARM Linux
[off-list ref] wrote:

On Tue, Jan 17, 2012 at 04:27:21PM +0000, Catalin Marinas wrote:

quoted

Anyway, the first step is this API provided by the secure firmware.
Since such API may need to be called before the MMU is initialised,
Linux would need to have knowledge of the platform type early on. Having
some platform hook (asm macro) to call early on wouldn't work with the
single zImage configuration. Stack space is not an issue as we already
have one for ARMv7 for D-cache flushing (XIP kernels would work but they
aren't that many).

It _is_ a problem. ?How much stack space would these undefined platform
specific functions require? ?16 words? ?32 words? ?A page? ?Where does
this memory come from? ?The .data section, or are we going to stuff it
into what is supposed to be the read-only text section?

Stack requirement is limited to saving and restoring the processor
registers. There is no additional need. If this is an issue, we can also use
SRAM as a stack for this operation.

Regards
Santosh