Re: [PATCH v2 4/7] ARM: update MPIDR accessors macro

From: Christoffer Dall <christoffer.dall@linaro.org>
To: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: marc.zyngier@arm.com, andre.przywara@arm.com,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 4/7] ARM: update MPIDR accessors macro
Date: Mon, 5 Sep 2016 13:29:09 +0200	[thread overview]
Message-ID: <20160905112909.GI26366@cbox> (raw)
In-Reply-To: <1471344418-19568-5-git-send-email-vladimir.murzin@arm.com>

The title of this patch is quite generic, especially the 'update'.
Perhaps say: 

"ARM: Change MPIDR_AFFINITY_LEVEL to ignore Aff3"

On Tue, Aug 16, 2016 at 11:46:55AM +0100, Vladimir Murzin wrote:
> vgic-v3 driver queries CPU affinity level up to Aff3, which is valid for arm64.
> However, for arm up to Aff2 levels are supported, so querying for 3rd level
> ends with upper bits of MPIDR are treated as valid affinity level which
> is not true. So, report zero for any affinity level above 2.
> 
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
> ---
>  arch/arm/include/asm/cputype.h |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/include/asm/cputype.h b/arch/arm/include/asm/cputype.h
> index 1ee94c7..96cef49 100644
> --- a/arch/arm/include/asm/cputype.h
> +++ b/arch/arm/include/asm/cputype.h
> @@ -55,9 +55,10 @@
>  
>  #define MPIDR_LEVEL_BITS 8
>  #define MPIDR_LEVEL_MASK ((1 << MPIDR_LEVEL_BITS) - 1)
> +#define MPIDR_LEVEL_SHIFT(level) (MPIDR_LEVEL_BITS * level)
>  
>  #define MPIDR_AFFINITY_LEVEL(mpidr, level) \
> -	((mpidr >> (MPIDR_LEVEL_BITS * level)) & MPIDR_LEVEL_MASK)
> +	((level < 3) ? ((mpidr >> MPIDR_LEVEL_SHIFT(level)) & MPIDR_LEVEL_MASK) : 0)

Instead of using a conditional here, you could just apply the
MPIDR_HWID_BITMASK to the mpidr argument instead.

>  
>  #define ARM_CPU_IMP_ARM			0x41
>  #define ARM_CPU_IMP_INTEL		0x69
> -- 
> 1.7.9.5
> 