Re: [PATCH] MIPS: mm: tlbex: Replace cpu_has_mips_r2_exec_hazard with cpu_has_mips_r2_r6

[David Daney <ddaney@caviumnetworks.com>]

On 03/13/2015 07:44 AM, Ralf Baechle wrote:
> On Fri, Mar 13, 2015 at 09:18:08AM +0000, Markos Chandras wrote:
>
>> Commit 77f3ee59ee7cf ("MIPS: mm: tlbex: Use cpu_has_mips_r2_exec_hazard
>> for the EHB instruction") replaced cpu_has_mips_r2 with
>> cpu_has_mips_r2_exec_hazard to indicate whether the ISA has the EHB
>> instruction. However, the meaning of the cpu_has_mips_r2_exec_hazard
>> is different. It was meant to be used as an indication on whether the
>> running processor needs to run the EHB instruction instead of checking
>> whether the EHB is available on the ISA. This broke processors that do
>> not define cpu_has_mips_r2_exec_hazard. We fix this by replacing the
>> said macro with cpu_has_mips_r2_r6 which covers R2 and R6 processors.
>>
>> Fixes: 77f3ee59ee7cf ("MIPS: mm: tlbex: Use cpu_has_mips_r2_exec_hazard for the EHB instruction")
>> Cc: David Daney <david.daney@cavium.com>
>> Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
>
> Either of this David's revert or this patch applied will leave
> cpu_has_mips_r2_exec_hazard unused which at a glance doesn't seem to
> be right and defeats David's old patches 9e290a19 / 41f0e4d0 from working.
>
> cpu_has_mips_r2_exec_hazard was made unused by 625c0a21 which I think
> should be reverted and cpu_has_mips_r2_exec_hazard be defined to be something
> like
>
> #define cpu_has_mips_r2_exec_hazard					\
> ({									\
> 	int __res;							\
> 									\
> 	switch (current_cpu_type()) {					\
> 	case CPU_M14KC:							\
> 	case CPU74K:							\
> 	case CPU_CAVIUM_OCTEON:						\
> 	case CPU_CAVIUM_OCTEON_PLUS:					\
>          case CPU_CAVIUM_OCTEON2:					\
> 	case CPU_CAVIUM_OCTEON3:					\

The four octeon models are already covered in 
arch/mips/include/asm/mach-cavium-octeon/cpu-feature-overrides.h

> 		__res = 0;						\
> 		break;							\
> 									\
> 	default:							\
> 		__res = 1;						\
> 	}								\
> 									\
> 	__res;								\
> })
>
> ?
>

Something like that is needed somewhere

I would suggest having the default definition contain some 
generalizations about where it should return true, and 
arch/mips/include/asm/mach-*/cpu-feature-overrides.h isolate the 
specific models for each sub-architecture.

David Daney

>    Ralf
>