From: Marc Zyngier <maz@kernel.org>
To: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>,
mark.rutland@arm.com, suzuki.poulose@arm.com,
ionela.voinescu@arm.com, MSM <linux-arm-msm@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
catalin.marinas@arm.com, Will Deacon <will@kernel.org>,
valentin.schneider@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: AMU extension v1 support for cortex A76, A77, A78 CPUs
Date: Fri, 20 Nov 2020 09:54:48 +0000 [thread overview]
Message-ID: <d77713992e5abef5c6066d9f1939e8db@kernel.org> (raw)
In-Reply-To: <e15de351-63c1-2599-82bf-22c95e8a6a62@arm.com>
On 2020-11-20 09:09, Vladimir Murzin wrote:
> On 11/20/20 8:56 AM, Marc Zyngier wrote:
>> On 2020-11-20 04:30, Neeraj Upadhyay wrote:
>>> Hi,
>>>
>>> For ARM cortex A76, A77, A78 cores (which as per TRM, support AMU)
>>> AA64PFR0[47:44] field is not set, and AMU does not get enabled for
>>> them.
>>> Can you please provide support for these CPUs in cpufeature.c?
>>
>> If that was the case, that'd be an erratum, and it would need to be
>> documented as such. It could also be that this is an optional feature
>> for these cores (though the TRM doesn't suggest that).
>>
>> Can someone at ARM confirm what is the expected behaviour of these
>> CPUs?
>
> Not a confirmation, but IIRC, these are imp def features, while our
> cpufeatures
> catches architected one.
Ah, good point. So these CPUs implement some sort of AMU, and not *the*
AMU.
Yet the register names are the same. Who thought that'd be a good idea?
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2020-11-20 9:55 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-20 4:30 AMU extension v1 support for cortex A76, A77, A78 CPUs Neeraj Upadhyay
2020-11-20 8:56 ` Marc Zyngier
2020-11-20 9:09 ` Vladimir Murzin
2020-11-20 9:54 ` Marc Zyngier [this message]
2020-11-20 10:14 ` Vladimir Murzin
2020-11-20 10:13 ` Mark Rutland
2020-11-24 5:22 ` Neeraj Upadhyay
2020-11-20 10:20 ` Sudeep Holla
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