[PATCH] ARM: keystone: remove hand-coded smc instruction

[dave.martin@linaro.org (Dave Martin)]

On Fri, Jun 21, 2013 at 04:49:30PM -0400, Santosh Shilimkar wrote:
> On Friday 21 June 2013 04:35 PM, Arnd Bergmann wrote:
> > On Friday 21 June 2013, Arnd Bergmann wrote:
> >> This lets us build keystone with CONFIG_THUMB2_KERNEL enabled,
> >> without the patch we get this error:
> >>
> >> Error: cannot determine Thumb instruction size. Use .inst.n/.inst.w instead
> >>
> >> This follows the same change for all other platforms done
> >> earlier.
> >>
> >> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> >> Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
> >>
> >> diff --git a/arch/arm/mach-keystone/platsmp.c b/arch/arm/mach-keystone/platsmp.c
> >> index 630ab3bd..1800c33 100644
> >> --- a/arch/arm/mach-keystone/platsmp.c
> >> +++ b/arch/arm/mach-keystone/platsmp.c
> >> @@ -34,7 +34,7 @@ static int __cpuinit keystone_smp_boot_secondary(unsigned int cpu,
> >>  		"mov    r0, #0\n"	/* power on cmd	*/
> >>  		"mov    r1, %1\n"	/* cpu		*/
> >>  		"mov    r2, %2\n"	/* start	*/
> >> -		".inst  0xe1600070\n"	/* smc #0	*/
> >> +		"smc	#0\n"		/* smc #0	*/
> >>  		"mov    %0, r0\n"
> >>  		: "=r" (error)
> >>  		: "r"(cpu), "r"(start)
> > 
> > Ah, damm, now I get this error for building an ARMv6+ARMv7 combined kernel:
> > 
> > /tmp/ccSWHCik.s:55: Error: selected processor does not support ARM mode `smc #0'
> > 
> > I'll add a -march=armv7-a gcc flag as well.
> > 
> I was just typing about the error. I started with smc first but then
> hit the below one which lead me to write an opcode. I couldn't compile c file
> for v7 only build and hence letf it in encoded format.
> 
> I will be moving this code to separate asm file along with other smc
> API support.

I think the correct way to fix this is to use ".arch_extension sec" and "smc" in
the C inline asm, and put

	CFLAGS_platsmp.o := -march=armv7-a

in arch/arm/mach-keystone/Makefile

This approach is followed in a few other places.


Or put the SMC in a separate .S file with suitable AFLAGS if not on a
performance-critical hot path (for boot_secondary() it doesn't sounds
like a problem).

Cheers
---Dave