[PATCH 1/3] arm64: add MIDR_EL1 field accessors

[will.deacon@arm.com (Will Deacon)]

On Mon, May 12, 2014 at 03:37:48PM +0100, Mark Rutland wrote:
> The MIDR_EL1 register is composed of a number of bitfields, and uses of
> the fields has so far involved open-coding of the shifts and masks
> required.
> 
> This patch adds shifts and masks for each of the MIDR_EL1 subfields, and
> also provides accessors built atop of these. Existing uses within
> cputype.h are updated to use these accessors.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> ---
>  arch/arm64/include/asm/cputype.h | 27 +++++++++++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/cputype.h b/arch/arm64/include/asm/cputype.h
> index c404fb0..541b829 100644
> --- a/arch/arm64/include/asm/cputype.h
> +++ b/arch/arm64/include/asm/cputype.h
> @@ -36,6 +36,25 @@
>  	__val;								\
>  })
>  
> +#define MIDR_REVISION_MASK	0xf
> +#define MIDR_REVISION(midr)	((midr) & MIDR_REVISION_MASK)
> +#define MIDR_PARTNUM_SHIFT	4
> +#define MIDR_PARTNUM_MASK	(0xfff << MIDR_PARTNUM_SHIFT)
> +#define MIDR_PARTNUM(midr)	\
> +	(((midr) & MIDR_PARTNUM_MASK) >> MIDR_PARTNUM_SHIFT)
> +#define MIDR_ARCHITECTURE_SHIFT	16
> +#define MIDR_ARCHITECTURE_MASK	(0xf << MIDR_ARCHITECTURE_SHIFT)
> +#define MIDR_ARCHITECTURE(midr)	\
> +	(((midr) & MIDR_ARCHITECTURE_MASK) >> MIDR_ARCHITECTURE_SHIFT)
> +#define MIDR_VARIANT_SHIFT	20
> +#define MIDR_VARIANT_MASK	(0xf << MIDR_VARIANT_SHIFT)
> +#define MIDR_VARIANT(midr)	\
> +	(((midr) & MIDR_VARIANT_MASK) >> MIDR_VARIANT_SHIFT)
> +#define MIDR_IMPLEMENTOR_SHIFT	24
> +#define MIDR_IMPLEMENTOR_MASK	(0xff << MIDR_IMPLEMENTOR_SHIFT)
> +#define MIDR_IMPLEMENTOR(midr)	\
> +	(((midr) & MIDR_IMPLEMENTOR_MASK) >> MIDR_IMPLEMENTOR_SHIFT)
> +
>  #define ARM_CPU_IMP_ARM		0x41
>  #define ARM_CPU_IMP_APM		0x50
>  
> @@ -64,12 +83,16 @@ static inline u64 __attribute_const__ read_cpuid_mpidr(void)
>  
>  static inline unsigned int __attribute_const__ read_cpuid_implementor(void)
>  {
> -	return (read_cpuid_id() & 0xFF000000) >> 24;
> +	return MIDR_IMPLEMENTOR(read_cpuid_id());
>  }
>  
>  static inline unsigned int __attribute_const__ read_cpuid_part_number(void)
>  {
> -	return (read_cpuid_id() & 0xFFF0);
> +	/*
> +	 * The part number field is used in-place as a userspace ABI, so we
> +	 * cannot use MIDR_PARTNUM() here.
> +	 */
> +	return (read_cpuid_id() & MIDR_PARTNUM_MASK);

Where is this used as ABI? c_show is open-coded and kvm_target_cpu could
just add a shift left.

Will