linux-kernel - Re: [PATCH v3 2/3] riscv: add ISA extension parsing for bfloat16 ISA extension

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Message-ID: <374d3b07-e16c-4468-828a-a2a542cd88ac@rivosinc.com>
Date: Mon, 10 Feb 2025 15:38:58 +0100
From: Clément Léger <cleger@...osinc.com>
Cc: linux-doc@...r.kernel.org, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 Yixun Lan <dlan@...too.org>, Longbin Li <looong.bin@...il.com>,
 Jesse Taube <jesse@...osinc.com>, Yong-Xuan Wang <yongxuan.wang@...ive.com>,
 Samuel Holland <samuel.holland@...ive.com>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Evan Green <evan@...osinc.com>,
 Andrew Jones <ajones@...tanamicro.com>,
 Alexandre Ghiti <alexghiti@...osinc.com>, Andy Chiu <andybnac@...il.com>,
 Charlie Jenkins <charlie@...osinc.com>, Conor Dooley <conor+dt@...nel.org>,
 Rob Herring <robh@...nel.org>, Albert Ou <aou@...s.berkeley.edu>,
 Palmer Dabbelt <palmer@...belt.com>, Paul Walmsley
 <paul.walmsley@...ive.com>, Jonathan Corbet <corbet@....net>,
 Chen Wang <unicorn_wang@...look.com>, Inochi Amaoto <inochiama@...il.com>
Subject: Re: [PATCH v3 2/3] riscv: add ISA extension parsing for bfloat16 ISA
 extension



On 06/12/2024 06:58, Inochi Amaoto wrote:
> Add parsing for Zfbmin, Zvfbfmin, Zvfbfwma ISA extension which
> were ratified in 4dc23d62 ("Added Chapter title to BF16") of
> the riscv-isa-manual.
> 
> Signed-off-by: Inochi Amaoto <inochiama@...il.com>
> ---
>  arch/riscv/include/asm/hwcap.h | 3 +++
>  arch/riscv/kernel/cpufeature.c | 3 +++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
> index 869da082252a..14cc29f2a723 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -100,6 +100,9 @@
>  #define RISCV_ISA_EXT_ZICCRSE		91
>  #define RISCV_ISA_EXT_SVADE		92
>  #define RISCV_ISA_EXT_SVADU		93
> +#define RISCV_ISA_EXT_ZFBFMIN		94
> +#define RISCV_ISA_EXT_ZVFBFMIN		95
> +#define RISCV_ISA_EXT_ZVFBFWMA		96
>  
>  #define RISCV_ISA_EXT_XLINUXENVCFG	127
>  
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index c0916ed318c2..5cfcab139568 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -341,6 +341,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>  	__RISCV_ISA_EXT_DATA(zacas, RISCV_ISA_EXT_ZACAS),
>  	__RISCV_ISA_EXT_DATA(zawrs, RISCV_ISA_EXT_ZAWRS),
>  	__RISCV_ISA_EXT_DATA(zfa, RISCV_ISA_EXT_ZFA),
> +	__RISCV_ISA_EXT_DATA(zfbfmin, RISCV_ISA_EXT_ZFBFMIN),

Hi Inochi,

You could add a validation callback to that extension:

static int riscv_ext_f_depends(const struct riscv_isa_ext_data *data,
			       const unsigned long *isa_bitmap)
{
	if (__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_f))
		return 0;

	return -EPROBE_DEFER;
}

  ...
  __RISCV_ISA_EXT_DATA_VALIDATE(zfbfmin, RISCV_ISA_EXT_ZFBFMIN,
riscv_ext_f_depends),


But I'm ok with the current state of that patch since I have the same
thing coming for other extensions as well. So with or without my
previous comment fixed:

Reviewed-by: Clément Léger <cleger@...osinc.com>

Thanks,

Clément

>  	__RISCV_ISA_EXT_DATA(zfh, RISCV_ISA_EXT_ZFH),
>  	__RISCV_ISA_EXT_DATA(zfhmin, RISCV_ISA_EXT_ZFHMIN),
>  	__RISCV_ISA_EXT_DATA(zca, RISCV_ISA_EXT_ZCA),
> @@ -373,6 +374,8 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>  	__RISCV_ISA_EXT_SUPERSET(zve64d, RISCV_ISA_EXT_ZVE64D, riscv_zve64d_exts),
>  	__RISCV_ISA_EXT_SUPERSET(zve64f, RISCV_ISA_EXT_ZVE64F, riscv_zve64f_exts),
>  	__RISCV_ISA_EXT_SUPERSET(zve64x, RISCV_ISA_EXT_ZVE64X, riscv_zve64x_exts),
> +	__RISCV_ISA_EXT_DATA(zvfbfmin, RISCV_ISA_EXT_ZVFBFMIN),
> +	__RISCV_ISA_EXT_DATA(zvfbfwma, RISCV_ISA_EXT_ZVFBFWMA),
>  	__RISCV_ISA_EXT_DATA(zvfh, RISCV_ISA_EXT_ZVFH),
>  	__RISCV_ISA_EXT_DATA(zvfhmin, RISCV_ISA_EXT_ZVFHMIN),
>  	__RISCV_ISA_EXT_DATA(zvkb, RISCV_ISA_EXT_ZVKB),