[PATCH] ARM: Fix SMP_ON_UP for non ARM ltd. implementations

[Will Deacon]

> > As an optimisation, we could also check that bit 30 is zero so that
> > we patch out the SMP stuff for single-core A5/A9/A15. Up to you.
> 
> Ok, so with that added, it becomes:
> 
>  arch/arm/kernel/head.S |   22 ++++++++++------------
>  1 files changed, 10 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
> index f17d9a0..c0225da 100644
> --- a/arch/arm/kernel/head.S
> +++ b/arch/arm/kernel/head.S
> @@ -392,24 +392,22 @@ ENDPROC(__turn_mmu_on)
> 
>  #ifdef CONFIG_SMP_ON_UP
>  __fixup_smp:
> -	mov	r4, #0x00070000
> -	orr	r3, r4, #0xff000000	@ mask 0xff070000
> -	orr	r4, r4, #0x41000000	@ val 0x41070000
> -	and	r0, r9, r3
> -	teq	r0, r4			@ ARM CPU and ARMv6/v7?
> +	and	r3, r9, #0x000f0000	@ architecture version
> +	teq	r3, #0x000f0000		@ CPU ID supported?
>  	bne	__fixup_smp_on_up	@ no, assume UP
> 
> -	orr	r3, r3, #0x0000ff00
> -	orr	r3, r3, #0x000000f0	@ mask 0xff07fff0
> +	bic	r3, r9, #0x00ff0000
> +	bic	r3, r3, #0x0000000f	@ mask 0xff00fff0
> +	mov	r4, #0x41000000
>  	orr	r4, r4, #0x0000b000
> -	orr	r4, r4, #0x00000020	@ val 0x4107b020
> -	and	r0, r9, r3
> -	teq	r0, r4			@ ARM 11MPCore?
> +	orr	r4, r4, #0x00000020	@ val 0x4100b020
> +	teq	r3, r4			@ ARM 11MPCore?
>  	moveq	pc, lr			@ yes, assume SMP
> 
>  	mrc	p15, 0, r0, c0, c0, 5	@ read MPIDR
> -	tst	r0, #1 << 31
> -	movne	pc, lr			@ bit 31 => SMP
> +	and	r0, r0, #0xc0000000	@ multiprocessing extensions and
> +	teq	r0, #0x80000000		@ not part of a uniprocessor system?
> +	moveq	pc, lr			@ yes, assume SMP
> 
>  __fixup_smp_on_up:
>  	adr	r0, 1f

That should do the trick.

Acked-by: Will Deacon <will.deacon at arm.com>

Thanks,

Will