[PATCH] ARM: make head.S less dependent on the compile time PHYS_OFFSET define

[Russell King - ARM Linux]

On Thu, Jan 13, 2011 at 05:04:28PM -0500, Nicolas Pitre wrote:
> +	.macro phys_offset, rd
> +	mov	\rd, pc
> +	and	\rd, \rd, #0xf8000000
> +	.endm

We can do loads better than that, as the p2v fixup code has proven.
Now that r8 has been eliminated, I may rebase the p2v stuff ontop of
that commit, and move the computation of phys_offset out of the p2v
fixup code - and have it in r8 for __create_page_tables to use.

FYI, the real PHYS_OFFSET value can be found by (eg):

1:	.long	.
	.long	PAGE_OFFSET

	adr	r0, 1b
	ldmia	r0, {r1, r2}
	sub	r1, r0, r1
	add	r3, r2, r1

r1 now contains the offset between virtual and physical spaces, r2
contains the compile-time PAGE_OFFSET constant, and r3 the runtime
equivalent of PHYS_OFFSET.

None of this uses troublesome masking which will trip up on platforms
such as MSM - we really must stop writing code which assumes that
physical memory is aligned to >= 32MB.