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Date:   Wed, 21 Feb 2018 11:43:26 +0000
From:   James Hogan <jhogan@kernel.org>
To:     "Maciej W. Rozycki" <macro@mips.com>
Cc:     Huacai Chen <chenhc@lemote.com>,
        Ralf Baechle <ralf@linux-mips.org>,
        "Steven J . Hill" <Steven.Hill@cavium.com>,
        linux-mips@linux-mips.org, Fuxin Zhang <zhangfx@lemote.com>,
        Zhangjin Wu <wuzhangjin@gmail.com>
Subject: Re: [PATCH V2 12/12] MIPS: Loongson: Introduce and use WAR_LLSC_MB
Message-ID: <20180221114326.GJ6245@saruman>
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On Wed, Feb 21, 2018 at 10:09:06AM +0000, Maciej W. Rozycki wrote:
> On Tue, 20 Feb 2018, James Hogan wrote:
>=20
> > > diff --git a/arch/mips/loongson64/Platform b/arch/mips/loongson64/Pla=
tform
> > > index 0fce460..3700dcf 100644
> > > --- a/arch/mips/loongson64/Platform
> > > +++ b/arch/mips/loongson64/Platform
> > > @@ -23,6 +23,9 @@ ifdef CONFIG_CPU_LOONGSON2F_WORKAROUNDS
> > >  endif
> > > =20
> > >  cflags-$(CONFIG_CPU_LOONGSON3)	+=3D -Wa,--trap
> > > +ifneq ($(call as-option,-Wa$(comma)-mfix-loongson3-llsc,),)
> > > +  cflags-$(CONFIG_CPU_LOONGSON3) +=3D -Wa$(comma)-mno-fix-loongson3-=
llsc
> > > +endif
> >=20
> > Could this be a separate patch?
> >=20
> > This needs more explanation.
> > - What does this do exactly?
> > - Why are you turning *OFF* the compiler fix?
> > - Was some fix we don't want already in use by default?
>=20
>  FYI, support for `-mfix-loongson3-llsc' in GAS has only recently been=20
> proposed: <https://sourceware.org/ml/binutils/2018-01/msg00303.html> and=
=20
> is still pending review.

Thanks for that link Maciej. GNU changelogs are useless, so this is the
interesting bit:
> +@item -mfix-loongson3-llsc
> +@itemx -mno-fix-loongson3-llsc
> +Insert @code{sync} instruction before @samp{ll} or @samp{lld} instrction
> +to work around Loongson3 @samp{LL}/@samp{SC} errata.
> +This issue exists in all Loongson3 CPUs.

Cheers
James

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