linux-kernel - Re: [PATCH] ARM: Fix SMP_ON_UP for non ARM ltd. implementations

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Date:	Mon, 31 Jan 2011 13:33:30 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: Fix SMP_ON_UP for non ARM ltd. implementations

On 01/30/2011 08:40 AM, Russell King - ARM Linux wrote:
> 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

Great. Looks good to me too. If I had know that ARM 11MPCore had an 0xf
in the architecture bits I would have suggested this fix instead.

Also, I wasn't sure if we should send fixes for EXPERIMENTAL features to
the stable tree. If its appropriate, please Cc stable when the patch
goes in.

Reported-and-Tested-by: Stephen Boyd <sboyd@...eaurora.org>

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

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