[PATCH v3 6/7] arm64: Advertise ARM64_HAS_DCPODP cpu feature

[Dave Martin]

On Mon, Apr 01, 2019 at 11:45:14AM +0100, Andrew Murray wrote:
> Advertise ARM64_HAS_DCPOP when both DC CVAP and DC CVADP are supported.

Do you mean ARM64_HAS_DCPODP?

And do we need this?  This capability flag doesn't currently appear to
be used for anything (which makes me wonder whether it _should_ be wired
up to something in the kernel).

Do we expect the kernel to do something special with this in the future?

OTOH, we get a nice printk when the feature is detected, and the code
size cost is insignificant.  So, if there's a reasonable expectation that
we will use it someday, I don't see a big problem with having it.

Cheers
---Dave

> 
> Signed-off-by: Andrew Murray <andrew.murray@arm.com>
> ---
>  arch/arm64/include/asm/cpucaps.h | 3 ++-
>  arch/arm64/kernel/cpufeature.c   | 9 +++++++++
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
> index f6a76e43f39e..defdc67d9ab4 100644
> --- a/arch/arm64/include/asm/cpucaps.h
> +++ b/arch/arm64/include/asm/cpucaps.h
> @@ -61,7 +61,8 @@
>  #define ARM64_HAS_GENERIC_AUTH_ARCH		40
>  #define ARM64_HAS_GENERIC_AUTH_IMP_DEF		41
>  #define ARM64_HAS_IRQ_PRIO_MASKING		42
> +#define ARM64_HAS_DCPODP			43
>  
> -#define ARM64_NCAPS				43
> +#define ARM64_NCAPS				44
>  
>  #endif /* __ASM_CPUCAPS_H */
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 5e27d2dbe45e..c74b25895c43 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1339,6 +1339,15 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
>  		.field_pos = ID_AA64ISAR1_DPB_SHIFT,
>  		.min_field_value = 1,
>  	},
> +	{
> +		.desc = "Data cache clean to Point of Deep Persistence",
> +		.capability = ARM64_HAS_DCPODP,
> +		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
> +		.matches = has_cpuid_feature,
> +		.sys_reg = SYS_ID_AA64ISAR1_EL1,
> +		.field_pos = ID_AA64ISAR1_DPB_SHIFT,
> +		.min_field_value = 2,
> +	},
>  #endif
>  #ifdef CONFIG_ARM64_SVE
>  	{
> -- 
> 2.21.0
>