linux-kernel - Re: [PATCH] loongarch/crypto: Clean up useless assignment operations

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Date: Mon, 26 Feb 2024 16:15:42 +0800
From: WANG Xuerui <kernel@...0n.name>
To: WangYuli <wangyuli@...ontech.com>, herbert@...dor.apana.org.au,
 davem@...emloft.net, chenhuacai@...nel.org
Cc: linux-crypto@...r.kernel.org, loongarch@...ts.linux.dev,
 linux-kernel@...r.kernel.org, Guan Wentao <guanwentao@...ontech.com>
Subject: Re: [PATCH] loongarch/crypto: Clean up useless assignment operations

On 2/26/24 16:03, WangYuli wrote:
> Both crc32 and crc32c hw accelerated funcs will calculate the
> remaining len. Those codes are derived from
> arch/mips/crypto/crc32-mips.c and "len -= sizeof(u32)" is not
> necessary for 64-bit CPUs.
> 
> Removing it can make context code style more unified and improve
> code readability.
> 
> Suggested-by: Guan Wentao <guanwentao@...ontech.com>
> Signed-off-by: WangYuli <wangyuli@...ontech.com>
> ---
>   arch/loongarch/crypto/crc32-loongarch.c | 2 --
>   1 file changed, 2 deletions(-)
> 
> diff --git a/arch/loongarch/crypto/crc32-loongarch.c b/arch/loongarch/crypto/crc32-loongarch.c
> index a49e507af38c..3eebea3a7b47 100644
> --- a/arch/loongarch/crypto/crc32-loongarch.c
> +++ b/arch/loongarch/crypto/crc32-loongarch.c
> @@ -44,7 +44,6 @@ static u32 crc32_loongarch_hw(u32 crc_, const u8 *p, unsigned int len)
>   
>   		CRC32(crc, value, w);
>   		p += sizeof(u32);
> -		len -= sizeof(u32);
>   	}
>   
>   	if (len & sizeof(u16)) {
> @@ -80,7 +79,6 @@ static u32 crc32c_loongarch_hw(u32 crc_, const u8 *p, unsigned int len)
>   
>   		CRC32C(crc, value, w);
>   		p += sizeof(u32);
> -		len -= sizeof(u32);
>   	}
>   
>   	if (len & sizeof(u16)) {

Sure, but IIRC Loongson still has hopes in having 32-bit-only models 
support upstream? The possibility cannot be ruled out because from 
public information (e.g. the 2023-11-28 news event), Loongson is known 
to be actively licensing their reduced 32-bit-only IP cores to third 
parties.

Ultimately whether we want to imply 64-bit operation with the crc32 
module is up to Loongson to decide, and I think Huacai may have 
something to add, but IMO at least we could gate the statement with 
#ifdef's so we don't outright lose 32-bit compatibility with this code.

-- 
WANG "xen0n" Xuerui

Linux/LoongArch mailing list: https://lore.kernel.org/loongarch/