Subject: [PATCH] arm64: Add support for Half precision floating point

From: [email-masked] (Will Deacon)
Date: Tue, 26 Jan 2016 16:02:58 +0000

Hi Suzuki,

On Tue, Jan 26, 2016 at 03:52:46PM +0000, Suzuki K Poulose wrote:
> ARMv8.2 extensions [1] include an optional feature, which supports
> half precision(16bit) floating point/asimd data processing
> instructions. This patch adds support for detecting and exposing
> the same to the userspace via HWCAPs
> 
> [1] https://community.arm.com/groups/processors/blog/2016/01/05/armv8-a-architecture-evolution
> 
> Signed-off-by: Suzuki K. Poulose <[email-masked]>
> ---
>  arch/arm64/include/uapi/asm/hwcap.h |    2 ++
>  arch/arm64/kernel/cpufeature.c      |    2 ++
>  arch/arm64/kernel/cpuinfo.c         |    2 ++
>  3 files changed, 6 insertions(+)
> 
> diff --git a/arch/arm64/include/uapi/asm/hwcap.h b/arch/arm64/include/uapi/asm/hwcap.h
> index 361c8a8..a739287 100644
> --- a/arch/arm64/include/uapi/asm/hwcap.h
> +++ b/arch/arm64/include/uapi/asm/hwcap.h
> @@ -28,5 +28,7 @@
>  #define HWCAP_SHA2		(1 << 6)
>  #define HWCAP_CRC32		(1 << 7)
>  #define HWCAP_ATOMICS		(1 << 8)
> +#define HWCAP_FPHP		(1 << 9)
> +#define HWCAP_ASIMDHP		(1 << 10)

Where did we get to with the mrs trapping you proposed here?

  http://lists.infradead.org/pipermail/linux-arm-kernel/2015-October/374609.html

At some point, we need to consider whether or not we want to continue
adding new HWCAPs or whether your suggestion above is actually useful
to userspace.

Did the libc guys get anywhere with a prototype? What do we need to do
to make progress with it?

Will