Re: [PATCH v2] arm64: v8.4: Support for new floating point multiplication instructions

[Dave Martin]

On Tue, Dec 12, 2017 at 10:36:59PM +0800, Dongjiu Geng wrote:
> ARM v8.4 extensions add new neon instructions for performing a
> multiplication of each FP16 element of one vector with the corresponding
> FP16 element of a second vector, and to add or subtract this without an
> intermediate rounding to the corresponding FP32 element in a third vector.
> 
> This patch detects this feature and let the userspace know about it via a
> HWCAP bit and MRS emulation.
> 
> Cc: Dave Martin <Dave.Martin@xxxxxxx>
> Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> Signed-off-by: Dongjiu Geng <gengdongjiu@xxxxxxxxxx>
> ---
> Change since v1:
> 1. Address Dave and Suzuki's comments to update the commit message.
> 2. Address Dave's comments to update Documentation/arm64/elf_hwcaps.txt.
> ---
>  Documentation/arm64/cpu-feature-registers.txt | 4 +++-
>  Documentation/arm64/elf_hwcaps.txt            | 4 ++++
>  arch/arm64/include/asm/sysreg.h               | 1 +
>  arch/arm64/include/uapi/asm/hwcap.h           | 1 +
>  arch/arm64/kernel/cpufeature.c                | 2 ++
>  arch/arm64/kernel/cpuinfo.c                   | 1 +
>  6 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/arm64/cpu-feature-registers.txt b/Documentation/arm64/cpu-feature-registers.txt
> index bd9b3fa..a70090b 100644
> --- a/Documentation/arm64/cpu-feature-registers.txt
> +++ b/Documentation/arm64/cpu-feature-registers.txt
> @@ -110,7 +110,9 @@ infrastructure:
>       x--------------------------------------------------x
>       | Name                         |  bits   | visible |
>       |--------------------------------------------------|
> -     | RES0                         | [63-48] |    n    |
> +     | RES0                         | [63-52] |    n    |
> +     |--------------------------------------------------|
> +     | FHM                          | [51-48] |    y    |
>       |--------------------------------------------------|
>       | DP                           | [47-44] |    y    |
>       |--------------------------------------------------|
> diff --git a/Documentation/arm64/elf_hwcaps.txt b/Documentation/arm64/elf_hwcaps.txt
> index 89edba1..987c40e 100644
> --- a/Documentation/arm64/elf_hwcaps.txt
> +++ b/Documentation/arm64/elf_hwcaps.txt
> @@ -158,3 +158,7 @@ HWCAP_SHA512
>  HWCAP_SVE
>  
>      Functionality implied by ID_AA64PFR0_EL1.SVE == 0b0001.
> +
> +HWCAP_FHM

This needs to match the name of the #define in hwcap.h.

With that change, Reviewed-by: Dave Martin <Dave.Martin@xxxxxxx>

Cheers
---Dave


> +
> +   Functionality implied by ID_AA64ISAR0_EL1.FHM == 0b0001.
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 08cc885..1818077 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -419,6 +419,7 @@
>  #define SCTLR_EL1_CP15BEN	(1 << 5)
>  
>  /* id_aa64isar0 */
> +#define ID_AA64ISAR0_FHM_SHIFT		48
>  #define ID_AA64ISAR0_DP_SHIFT		44
>  #define ID_AA64ISAR0_SM4_SHIFT		40
>  #define ID_AA64ISAR0_SM3_SHIFT		36
> diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
> index cda76fa..f018c3d 100644
> --- a/arch/arm64/include/uapi/asm/hwcap.h
> +++ b/arch/arm64/include/uapi/asm/hwcap.h
> @@ -43,5 +43,6 @@
>  #define HWCAP_ASIMDDP		(1 << 20)
>  #define HWCAP_SHA512		(1 << 21)
>  #define HWCAP_SVE		(1 << 22)
> +#define HWCAP_ASIMDFHM		(1 << 23)
>  
>  #endif /* _UAPI__ASM_HWCAP_H */
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index c5ba009..bc7e707 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -123,6 +123,7 @@ static int __init register_cpu_hwcaps_dumper(void)
>   * sync with the documentation of the CPU feature register ABI.
>   */
>  static const struct arm64_ftr_bits ftr_id_aa64isar0[] = {
> +	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_FHM_SHIFT, 4, 0),
>  	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_DP_SHIFT, 4, 0),
>  	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_SM4_SHIFT, 4, 0),
>  	ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64ISAR0_SM3_SHIFT, 4, 0),
> @@ -991,6 +992,7 @@ static bool has_no_fpsimd(const struct arm64_cpu_capabilities *entry, int __unus
>  	HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_SM3_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_SM3),
>  	HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_SM4_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_SM4),
>  	HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_DP_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_ASIMDDP),
> +	HWCAP_CAP(SYS_ID_AA64ISAR0_EL1, ID_AA64ISAR0_FHM_SHIFT, FTR_UNSIGNED, 1, CAP_HWCAP, HWCAP_ASIMDFHM),
>  	HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_FP_SHIFT, FTR_SIGNED, 0, CAP_HWCAP, HWCAP_FP),
>  	HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_FP_SHIFT, FTR_SIGNED, 1, CAP_HWCAP, HWCAP_FPHP),
>  	HWCAP_CAP(SYS_ID_AA64PFR0_EL1, ID_AA64PFR0_ASIMD_SHIFT, FTR_SIGNED, 0, CAP_HWCAP, HWCAP_ASIMD),
> diff --git a/arch/arm64/kernel/cpuinfo.c b/arch/arm64/kernel/cpuinfo.c
> index 1e25545..7f94623 100644
> --- a/arch/arm64/kernel/cpuinfo.c
> +++ b/arch/arm64/kernel/cpuinfo.c
> @@ -76,6 +76,7 @@
>  	"asimddp",
>  	"sha512",
>  	"sve",
> +	"asimdfhm",
>  	NULL
>  };
>  
> -- 
> 1.9.1
> 
> 
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