Re: [CFT] Always enable SMP mode on MP capable CPUs

From: afzal mohammed <afzal.mohd.ma@gmail.com>
To: linux-omap@vger.kernel.org
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [CFT] Always enable SMP mode on MP capable CPUs
Date: Wed, 24 May 2017 21:20:45 +0530	[thread overview]
Message-ID: <20170524155045.GA4082@afzalpc> (raw)
In-Reply-To: <20170518105209.GN22219@n2100.armlinux.org.uk>

To make those handling AM43x aware, To'ing l-o

Hi,

On Thu, May 18, 2017 at 11:52:10AM +0100, 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@armlinux.org.uk>
> ---

> 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.

With this change, AM437x, i.e. the above mentioned SoC stops
booting (multi_v7 config)

afzal

> 
>  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
>  
>  /*
> 
> -- 
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
> according to speedtest.net.
> 
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