Date: Wed, 27 Sep 2017 14:39:32 +0100
From: Mark Rutland <mark.rutland@arm.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Al Stone <ahs3@redhat.com>, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>
Subject: Re: [PATCH 3/3] arm64: cpuinfo: display product info in /proc/cpuinfo
Message-ID: <20170927133931.GH32150@leverpostej>
References: <20170926222324.17409-1-ahs3@redhat.com>
 <20170926222324.17409-4-ahs3@redhat.com>
 <f09e55d8-28ba-30e3-d58a-ad125fd73019@arm.com>
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Hi,

On Wed, Sep 27, 2017 at 11:42:07AM +0100, Robin Murphy wrote:
> On 26/09/17 23:23, Al Stone wrote:
> > +			seq_printf(m, ", ARM 8.%d (r%dp%d) CPU",
> > +				   MIDR_VARIANT(midr),
> > +				   MIDR_VARIANT(midr),
> > +				   MIDR_REVISION(midr));
> 
> What is "ARM 8.1" meant to infer for, say, a typical Cortex-A57?

Just to make Robin's point a little clearer, MIDR_EL1.Variant is
IMPLEMENTATION DEFINED, and doesn't describe the ARMv8.x architecture
revision.

For example, on Cortex A57 is contains the major revision number of the
CPU, and is 1 for any r1pY Cortex-A57 (e.g. those on Juno R1).

For better or worse, the architecture provides us no mechanism to
determine the architecture revision.

Thanks,
Mark.