[PATCH v2] ARM: Define wfi() macro for v6 processors

On Tuesday 08 February 2011 17:32:29 Russell King - ARM Linux wrote:

On Tue, Feb 08, 2011 at 04:17:58PM +0100, Arnd Bergmann wrote:

quoted

On Tuesday 08 February 2011, Dave Martin wrote:

quoted

CFLAGS_cpu_specific_object.o        += -march=armv7-a

Whether it's safe to do it depends on whether code from that file
could ever get run on other processors.  I'm not so sure of the answer
to that..., but perhaps someone else has a better idea.

We already do this a lot from arch/arm/mm/Makefile, and those
files are typically just one function per file, so they can easily
be proven to be safe that way.

No, we do that with assembly files.  It doesn't work soo well with
C files as we really don't want GCC itself to generate v7 instructions
unless we explicitly ask for them.

The other issue here is that somtimes generating code with different
-march options leads to the linker refusing to link them together...

Ok, I see. Is that a bug in existing toolchains, or something more
fundamental?

I would have expected that you could at least mix all compiler options
that don't impact the ABI or the instruction set like -mthumb.

Also, I think we can still build with e.g. "-march=armv6 -Wa,-march=armv7",
which should tell the compiler to only emit armv6 instructions, but make
the assembler more permissive for inline assembly.

	Arnd