linux-kernel - Re: [PATCH] mips: remove reference to "newer Loongson-3"

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Message-ID: <b32c0d64-77b2-d054-afcf-7d006eba3418@flygoat.com>
Date:   Mon, 30 Aug 2021 10:32:03 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     Xi Ruoyao <xry111@...gyan1223.wang>, linux-mips@...r.kernel.org
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-kernel@...r.kernel.org, Huacai Chen <chenhuacai@...nel.org>
Subject: Re: [PATCH] mips: remove reference to "newer Loongson-3"


在 2021/8/29 20:49, Xi Ruoyao 写道:
> Newest Loongson-3 processors have moved to use LoongArch architecture.
> Sadly, the LL/SC issue is still existing on both latest Loongson-3
> processors using MIPS64 (Loongson-3A4000) and LoongArch
> (Loongson-3A5000).
LLSC is fixed on Loongson-3A4000 as per CPUCFG report.
>
> As it's very unlikely there will be new Loongson-3 processors using
> MIPS64, let's stop people from false hoping.
>
> Signed-off-by: Xi Ruoyao <xry111@...gyan1223.wang>
> Cc: Huacai Chen <chenhuacai@...nel.org>
> ---
>
> Huacai: how's the status of LL/SC issue on Loongson-2K?  If
> the issue exists on it as well, we can just force
> CPU_LOONGSON3_WORKAROUNDS when CONFIG_CPU_LOONGSON64 and
> CONFIG_SMP are both selected.

Loongson-2K do need LLSC workaround, although the reason behind the 
workaround seems different...

Thanks.

- Jiaxun

>
>   arch/mips/Kconfig | 9 ++-------
>   1 file changed, 2 insertions(+), 7 deletions(-)
>
> diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> index 6dfb27d531dd..ff5f344a371e 100644
> --- a/arch/mips/Kconfig
> +++ b/arch/mips/Kconfig
> @@ -1433,19 +1433,14 @@ config LOONGSON3_ENHANCEMENT
>   	  new Loongson-3 machines only, please say 'Y' here.
>   
>   config CPU_LOONGSON3_WORKAROUNDS
> -	bool "Old Loongson-3 LLSC Workarounds"
> +	bool "Loongson-3 LLSC Workarounds"
>   	default y if SMP
>   	depends on CPU_LOONGSON64
>   	help
>   	  Loongson-3 processors have the llsc issues which require workarounds.
>   	  Without workarounds the system may hang unexpectedly.
>   
> -	  Newer Loongson-3 will fix these issues and no workarounds are needed.
> -	  The workarounds have no significant side effect on them but may
> -	  decrease the performance of the system so this option should be
> -	  disabled unless the kernel is intended to be run on old systems.
> -
> -	  If unsure, please say Y.
> +	  Say Y, unless you know what you are doing.
>   
>   config CPU_LOONGSON3_CPUCFG_EMULATION
>   	bool "Emulate the CPUCFG instruction on older Loongson cores"