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

From: [email-masked] (Santosh Shilimkar)
Date: Tue, 25 Jun 2013 10:10:45 -0400

On Tuesday 25 June 2013 10:07 AM, Dave Martin wrote:
> 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 <[email-masked]>
>>>> Cc: Santosh Shilimkar <[email-masked]>
>>>>
>>>> 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).
> 
Yep. Separate .S file patch is already submitted. Thanks

Regards,
Santosh