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From:   Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
To:     Vineet Gupta <Vineet.Gupta1@synopsys.com>
CC:     Alexey Brodkin <Alexey.Brodkin@synopsys.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-snps-arc@lists.infradead.org" 
        <linux-snps-arc@lists.infradead.org>
Subject: Re: [PATCH] ARC: guard dsp early init against non ARCv2
Thread-Topic: [PATCH] ARC: guard dsp early init against non ARCv2
Thread-Index: AQHWHY4Y5ZyBXjai50SPknapsyYH3KiO8C2AgAFm5lA=
Date:   Wed, 29 Apr 2020 17:12:54 +0000
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Hi Vineet, =0A=
=0A=
> From: Vineet Gupta <vgupta@synopsys.com>=0A=
> Sent: Tuesday, April 28, 2020 22:46=0A=
> To: Eugeniy Paltsev; linux-snps-arc@lists.infradead.org=0A=
> Cc: Alexey Brodkin; linux-kernel@vger.kernel.org=0A=
> Subject: Re: [PATCH] ARC: guard dsp early init against non ARCv2=0A=
> =0A=
> On 4/28/20 11:50 AM, Eugeniy Paltsev wrote:=0A=
> > As of today we guard early DSP init code with=0A=
> > ARC_AUX_DSP_BUILD (0x7A) BCR check to verify that we have=0A=
> > CPU with DSP configured. However that's not enough as in=0A=
> > ARCv1 CPU the same BCR (0x7A) is used for checking MUL/MAC=0A=
> > instructions presence.=0A=
> >=0A=
> > So, let's guard DSP early init against non ARCv2.=0A=
> >=0A=
> > Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>=0A=
> > ---=0A=
> >  arch/arc/include/asm/dsp-impl.h | 2 ++=0A=
> >  1 file changed, 2 insertions(+)=0A=
> >=0A=
> > diff --git a/arch/arc/include/asm/dsp-impl.h b/arch/arc/include/asm/dsp=
-impl.h=0A=
> > index e1aa212ca6eb..e64d945ae7df 100644=0A=
> > --- a/arch/arc/include/asm/dsp-impl.h=0A=
> > +++ b/arch/arc/include/asm/dsp-impl.h=0A=
> > @@ -15,12 +15,14 @@=0A=
> >=0A=
> >  /* clobbers r5 register */=0A=
> >  .macro DSP_EARLY_INIT=0A=
> > +#if defined(CONFIG_ISA_ARCV2)=0A=
> =0A=
> ifdef is the canonical way for a single macro to check.=0A=
> =0A=
> Also, this needs to be finer grained, i.e. CONFIG_ARC_DSP_KERNEL which is=
 already=0A=
> tied to ARCV2 only configs.=0A=
=0A=
We shouldn't limit the scope of this code part [dsp early init] to the case=
s=0A=
were DSP support is enabled in kconfig - and that is the reason why this co=
de=0A=
initially was guarded with BCR check only.=0A=
=0A=
So, I change the check to=0A=
=0A=
#if defined(CONFIG_ARC_DSP_HANDLED) || defined(CONFIG_ARC_DSP_NONE)=0A=
=0A=
which is actually the equivalent to=0A=
=0A=
#if defined(CONFIG_ISA_ARCV2)=0A=
=0A=
but I don't think it's worth thing to do.=0A=
=0A=
> =0A=
> >       lr      r5, [ARC_AUX_DSP_BUILD]=0A=
> >       bmsk    r5, r5, 7=0A=
> >       breq    r5, 0, 1f=0A=
> >       mov     r5, DSP_CTRL_DISABLED_ALL=0A=
> >       sr      r5, [ARC_AUX_DSP_CTRL]=0A=
> >  1:=0A=
> > +#endif=0A=
> >  .endm=0A=
> >=0A=
> >  /* clobbers r10, r11 registers pair */=0A=
=0A=
---=0A=
 Eugeniy Paltsev=