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

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Message-ID: <20250211-dizziness-eclair-2ef49cc5ad0e@spud>
Date: Tue, 11 Feb 2025 13:45:06 +0000
From: Conor Dooley <conor@...nel.org>
To: Inochi Amaoto <inochiama@...il.com>
Cc: Clément Léger <cleger@...osinc.com>,
	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>
Subject: Re: [PATCH v3 2/3] riscv: add ISA extension parsing for bfloat16 ISA
 extension

On Tue, Feb 11, 2025 at 08:42:39AM +0800, Inochi Amaoto wrote:
> On Mon, Feb 10, 2025 at 03:38:58PM +0100, Clément Léger wrote:
> > 
> > 
> > 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. 
> 
> 
> I think it is good for me to add the check, and I wonder it is possible
> to add the extra check for zvfbfmin and zvfbfwma like this:
> 
> static int riscv_ext_zvfbfmin_validate(const struct riscv_isa_ext_data *data,
> 				       const unsigned long *isa_bitmap)
> {
> 	if (__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_v))
> 		return 0;

This is not needed I think, V "turns on" Zve32f. If anything, you should
be checking for CONFIG_RISCV_ISA_V here ^^

You /could/ call the resulting riscv_vector_f_validate(), since this is
nothing specific to Zvfvfmin, and could be used for another extension
that requires a Zve32f or Zve64 minimum base.

> 
> 	if (__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZVE32F))
> 		return 0;
> 
> 	return -EPROBE_DEFER;
> }
> 
> static int riscv_ext_zvfbfwma_validate(const struct riscv_isa_ext_data *data,
> 				       const unsigned long *isa_bitmap)
> {
> 	if (__riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZFBFMIN) &&
> 	    __riscv_isa_extension_available(isa_bitmap, RISCV_ISA_EXT_ZVFBFMIN))
> 		return 0;
> 
> 	return -EPROBE_DEFER;
> }
> 
> > So with or without my previous comment fixed:
> > 
> > Reviewed-by: Clément Léger <cleger@...osinc.com>
> > 
> > Thanks,
> > 
> > Clément
> > 
> 
> Thanks,
> 
> Regards,
> Inochi
> 
> > >  	__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),
> > 

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