linux-kernel - Re: [PATCH] ARC: guard dsp early init against non ARCv2

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Date:   Tue, 28 Apr 2020 19:46:01 +0000
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
CC:     Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARC: guard dsp early init against non ARCv2

On 4/28/20 11:50 AM, Eugeniy Paltsev wrote:
> As of today we guard early DSP init code with
> ARC_AUX_DSP_BUILD (0x7A) BCR check to verify that we have
> CPU with DSP configured. However that's not enough as in
> ARCv1 CPU the same BCR (0x7A) is used for checking MUL/MAC
> instructions presence.
>
> So, let's guard DSP early init against non ARCv2.
>
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> ---
>  arch/arc/include/asm/dsp-impl.h | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/arc/include/asm/dsp-impl.h b/arch/arc/include/asm/dsp-impl.h
> index e1aa212ca6eb..e64d945ae7df 100644
> --- a/arch/arc/include/asm/dsp-impl.h
> +++ b/arch/arc/include/asm/dsp-impl.h
> @@ -15,12 +15,14 @@
>  
>  /* clobbers r5 register */
>  .macro DSP_EARLY_INIT
> +#if defined(CONFIG_ISA_ARCV2)

ifdef is the canonical way for a single macro to check.

Also, this needs to be finer grained, i.e. CONFIG_ARC_DSP_KERNEL which is already
tied to ARCV2 only configs.

>  	lr	r5, [ARC_AUX_DSP_BUILD]
>  	bmsk	r5, r5, 7
>  	breq    r5, 0, 1f
>  	mov	r5, DSP_CTRL_DISABLED_ALL
>  	sr	r5, [ARC_AUX_DSP_CTRL]
>  1:
> +#endif
>  .endm
>  
>  /* clobbers r10, r11 registers pair */