[CFT] Always enable SMP mode on MP capable CPUs

[Florian Fainelli]

On 05/18/2017 03:52 AM, Russell King - ARM Linux wrote:
> As a result of a recent bug report, it has been found that certain CPUs
> must always have SMP mode enabled in order for the caches to work.
> 
> Remove the conditional on setting the SMP bit(s).
> 
> Signed-off-by: Russell King <rmk+kernel at armlinux.org.uk>
> ---
> This needs to be tested on:
> 
> - Cortex A5MP
> - Cortex A9MP
> - Cortex R7MP
> - Cortex A7MP
> - Cortex A12MP
> - Cortex A15MP
> - Cortex A17MP
> - Brahma B15

Sorry just saw this, what kind of test do you want me to run on B15?
Should I build a !SMP kernel, or force a SMP kernel with maxcpus=1?

> 
> and any other CPU that mis-identifies itself with a MP-capable CPUID
> signature that might match one of those CPUs.  I'm aware of a Cortex
> A9 CPU out there that does mis-identify itself as SMP capable but
> isn't:
> 
>         @ Core indicates it is SMP. Check for Aegis SOC where a single
>         @ Cortex-A9 CPU is present but SMP operations fault.
> 
> This will also need testing.
> 
>  arch/arm/mm/proc-v7.S | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
> index 01d64c0b2563..4d48a4cf563b 100644
> --- a/arch/arm/mm/proc-v7.S
> +++ b/arch/arm/mm/proc-v7.S
> @@ -286,14 +286,10 @@ ENDPROC(cpu_pj4b_do_resume)
>  	stmia	r12, {r1-r6, lr}		@ v7_invalidate_l1 touches r0-r6
>  	bl      v7_invalidate_l1
>  	ldmia	r12, {r1-r6, lr}
> -#ifdef CONFIG_SMP
> +	mrc	p15, 0, r0, c1, c0, 1
>  	orr	r10, r10, #(1 << 6)		@ Enable SMP/nAMP mode
> -	ALT_SMP(mrc	p15, 0, r0, c1, c0, 1)
> -	ALT_UP(mov	r0, r10)		@ fake it for UP
>  	orr	r10, r10, r0			@ Set required bits
> -	teq	r10, r0				@ Were they already set?
> -	mcrne	p15, 0, r10, c1, c0, 1		@ No, update register
> -#endif
> +	mcr	p15, 0, r10, c1, c0, 1		@ No, update register
>  	b	__v7_setup_cont
>  
>  /*
> 


-- 
Florian