Re: [PATCH 2/6] arm64/cpufeature: Add DIT and CSV2 feature bits in ID_PFR0 register

[Will Deacon]

On Tue, Jan 28, 2020 at 06:09:05PM +0530, Anshuman Khandual wrote:
> Enable DIT and CSV2 feature bits in ID_PFR0 register as per ARM DDI 0487E.a
> specification. Except RAS and AMU, all other feature bits are now enabled.
> 
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> ---
>  arch/arm64/include/asm/sysreg.h | 3 +++
>  arch/arm64/kernel/cpufeature.c  | 2 ++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 054aab7ebf1b..469d61c8fabf 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -718,6 +718,9 @@
>  #define ID_ISAR6_DP_SHIFT		4
>  #define ID_ISAR6_JSCVT_SHIFT		0
>  
> +#define ID_PFR0_DIT_SHIFT		24
> +#define ID_PFR0_CSV2_SHIFT		16
> +
>  #define ID_PFR2_SSBS_SHIFT		4
>  #define ID_PFR2_CSV3_SHIFT		0
>  
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index c1e837fc8f97..9e4dab15c608 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -341,6 +341,8 @@ static const struct arm64_ftr_bits ftr_id_isar6[] = {
>  };
>  
>  static const struct arm64_ftr_bits ftr_id_pfr0[] = {
> +	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_PFR0_DIT_SHIFT, 4, 0),
> +	ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, ID_PFR0_CSV2_SHIFT, 4, 0),

Same comment as CSV3 here. Why is CSV2 being treated as strict here, but not
in the aa64* register?

Will