linux-kernel - Re: [PATCH v5 1/6] riscv: asm: alternative-macros: Introduce ALTERNATIVE

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Message-ID: <Y543kM4070CSDtZi@spud>
Date:   Sat, 17 Dec 2022 21:41:36 +0000
From:   Conor Dooley <conor@...nel.org>
To:     Prabhakar <prabhakar.csengg@...il.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Samuel Holland <samuel@...lland.org>,
        Guo Ren <guoren@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jisheng Zhang <jszhang@...nel.org>,
        Atish Patra <atishp@...osinc.com>,
        Anup Patel <apatel@...tanamicro.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Philipp Tomsich <philipp.tomsich@...ll.eu>,
        devicetree@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Biju Das <biju.das.jz@...renesas.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v5 1/6] riscv: asm: alternative-macros: Introduce
 ALTERNATIVE_3() macro

On Mon, Dec 12, 2022 at 11:55:00AM +0000, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> 
> Introduce ALTERNATIVE_3() macro.
> 
> A vendor wants to replace an old_content, but another vendor has used
> ALTERNATIVE_2() to patch its customized content at the same location.
> In this case, this vendor can use macro ALTERNATIVE_3() and then replace
> ALTERNATIVE_2() with ALTERNATIVE_3() to append its customized content.
> 
> While at it update comment above ALTERNATIVE_2() macro and make it generic
> so that the comment holds good for any new addition of ALTERNATIVE_X()
> macros.
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
> v4->v5
> * Rebased the patch on top of Andrew's series (now in Palmers for next-branch)
> * Updated comment for ALTERNATIVE_x() as suggested by Heiko
> 
> RFC v3 -> v4
> * New patch
> ---
>  arch/riscv/include/asm/alternative-macros.h | 46 ++++++++++++++++++---
>  1 file changed, 41 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/alternative-macros.h b/arch/riscv/include/asm/alternative-macros.h
> index 7226e2462584..a5b4691520da 100644
> --- a/arch/riscv/include/asm/alternative-macros.h
> +++ b/arch/riscv/include/asm/alternative-macros.h
> @@ -50,8 +50,17 @@
>  	ALT_NEW_CONTENT \vendor_id_2, \errata_id_2, \enable_2, \new_c_2
>  .endm
>  
> +.macro ALTERNATIVE_CFG_3 old_c, new_c_1, vendor_id_1, errata_id_1, enable_1,	\
> +				new_c_2, vendor_id_2, errata_id_2, enable_2,	\
> +				new_c_3, vendor_id_3, errata_id_3, enable_3
> +       ALTERNATIVE_CFG_2 \old_c, \new_c_1, \vendor_id_1, \errata_id_1, \enable_1,	\
> +                                 \new_c_2, \vendor_id_2, \errata_id_2, \enable_2
> +       ALT_NEW_CONTENT \vendor_id_3, \errata_id_3, \enable_3, \new_c_3
> +.endm
> +
>  #define __ALTERNATIVE_CFG(...)		ALTERNATIVE_CFG __VA_ARGS__
>  #define __ALTERNATIVE_CFG_2(...)	ALTERNATIVE_CFG_2 __VA_ARGS__
> +#define __ALTERNATIVE_CFG_3(...)	ALTERNATIVE_CFG_3 __VA_ARGS__
>  
>  #else /* !__ASSEMBLY__ */
>  
> @@ -98,6 +107,13 @@
>  	__ALTERNATIVE_CFG(old_c, new_c_1, vendor_id_1, errata_id_1, enable_1)	\
>  	ALT_NEW_CONTENT(vendor_id_2, errata_id_2, enable_2, new_c_2)
>  
> +#define __ALTERNATIVE_CFG_3(old_c, new_c_1, vendor_id_1, errata_id_1, enable_1,	\
> +				   new_c_2, vendor_id_2, errata_id_2, enable_2,	\
> +				   new_c_3, vendor_id_3, errata_id_3, enable_3)	\
> +	__ALTERNATIVE_CFG_2(old_c, new_c_1, vendor_id_1, errata_id_1, enable_1,	\
> +                                   new_c_2, vendor_id_2, errata_id_2, enable_2)	\
> +	ALT_NEW_CONTENT(vendor_id_3, errata_id_3, enable_3, new_c_3)
> +
>  #endif /* __ASSEMBLY__ */
>  
>  #define _ALTERNATIVE_CFG(old_c, new_c, vendor_id, errata_id, CONFIG_k)	\
> @@ -108,6 +124,13 @@
>  	__ALTERNATIVE_CFG_2(old_c, new_c_1, vendor_id_1, errata_id_1, IS_ENABLED(CONFIG_k_1),	\
>  				   new_c_2, vendor_id_2, errata_id_2, IS_ENABLED(CONFIG_k_2))
>  
> +#define _ALTERNATIVE_CFG_3(old_c, new_c_1, vendor_id_1, errata_id_1, CONFIG_k_1,		\
> +				  new_c_2, vendor_id_2, errata_id_2, CONFIG_k_2,		\
> +				  new_c_3, vendor_id_3, errata_id_3, CONFIG_k_3)		\
> +	__ALTERNATIVE_CFG_3(old_c, new_c_1, vendor_id_1, errata_id_1, IS_ENABLED(CONFIG_k_1),	\
> +				   new_c_2, vendor_id_2, errata_id_2, IS_ENABLED(CONFIG_k_2),	\
> +				   new_c_3, vendor_id_3, errata_id_3, IS_ENABLED(CONFIG_k_3))
> +
>  #else /* CONFIG_RISCV_ALTERNATIVE */
>  #ifdef __ASSEMBLY__
>  
> @@ -152,15 +175,28 @@
>  	_ALTERNATIVE_CFG(old_content, new_content, vendor_id, errata_id, CONFIG_k)
>  
>  /*
> - * A vendor wants to replace an old_content, but another vendor has used
> - * ALTERNATIVE() to patch its customized content at the same location. In
> - * this case, this vendor can create a new macro ALTERNATIVE_2() based
> - * on the following sample code and then replace ALTERNATIVE() with
> - * ALTERNATIVE_2() to append its customized content.
> + * ALTERNATIVE_x macros allow providing multiple replacement options
> + * for an ALTERNATIVE code section. This is helpful if multiple
> + * implementation variants for the same functionality exist for
> + * different cpu cores.

I think this last sentence should be:
"This is helpful if multiple implementation variants exist for the same
functionality."
I don't think CPU cores is the right level of "granularity".

> + *
> + * Usage:
> + *   ALTERNATIVE_x(old_content,
> + *      new_content1, vendor_id1, errata_id1, CONFIG_k1,
> + *      new_content2, vendor_id2, errata_id2, CONFIG_k2,
> + *      ...
> + *      new_contentx, vendor_idx, errata_idx, CONFIG_kx)
>   */
>  #define ALTERNATIVE_2(old_content, new_content_1, vendor_id_1, errata_id_1, CONFIG_k_1,		\
>  				   new_content_2, vendor_id_2, errata_id_2, CONFIG_k_2)		\
>  	_ALTERNATIVE_CFG_2(old_content, new_content_1, vendor_id_1, errata_id_1, CONFIG_k_1,	\
>  					new_content_2, vendor_id_2, errata_id_2, CONFIG_k_2)
>  
> +#define ALTERNATIVE_3(old_content, new_content_1, vendor_id_1, errata_id_1, CONFIG_k_1,		\
> +				   new_content_2, vendor_id_2, errata_id_2, CONFIG_k_2,		\
> +				   new_content_3, vendor_id_3, errata_id_3, CONFIG_k_3)		\
> +       _ALTERNATIVE_CFG_3(old_content, new_content_1, vendor_id_1, errata_id_1, CONFIG_k_1,	\
> +                                       new_content_2, vendor_id_2, errata_id_2, CONFIG_k_2,	\
> +                                       new_content_3, vendor_id_3, errata_id_3, CONFIG_k_3)

btw, why is this indented with spaces when the line above it is indented
with tabs? (At least, that is how it appears in mutt).

With those minor bits & the suggested fixes from Drew/Geert:
Reviewed-by: Conor Dooley <conor.dooley@...rochip.com>

Thanks,
Conor.

> +
>  #endif
> -- 
> 2.25.1
> 

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