linux-kernel - Re: [PATCH] Remove ARM errata Workarounds 458693 and 460075

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Date:   Tue, 2 May 2017 13:27:54 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Russell King - ARM Linux <linux@...linux.org.uk>
Cc:     vladimir.murzin@....com, linux-kernel@...r.kernel.org,
        dianders@...omium.org, kever.yang@...k-chips.com,
        linux-arm-kernel@...ts.infradead.org, armlinux@...isordat.com,
        Nisal Menuka <nisalmenuka23@...il.com>
Subject: Re: [PATCH] Remove ARM errata Workarounds 458693 and 460075

On 18/04/17 16:57, Catalin Marinas wrote:
> On Sun, Apr 16, 2017 at 09:04:46AM +0100, Russell King - ARM Linux wrote:
>> On Sat, Apr 15, 2017 at 07:06:06PM -0500, Nisal Menuka wrote:
>>> According to ARM, these errata exist only in a version of Cortex-A8
>>> (r2p0) which was never built. Therefore, I believe there are no platforms
>>> where this workaround should be enabled.
>>> link :http://infocenter.arm.com/help/index.jsp?topic=
>>> /com.arm.doc.faqs/ka15634.html
>>
>> These were submitted by ARM Ltd back in 2009 - if the silicon was never
>> built, there would've been no reason to submit them.  Maybe Catalin can
>> shed some light on this, being the commit author who introduced these?
> 
> We normally try not to submit errata workarounds for revisions that are
> not going to be built/deployed. It's possible that at the time there
> were plans for r2p0 to be licensed and built (not just FPGA) but I don't
> really remember the details. The A8 errata document indeed states that
> r1p0 and r2p0 are obsolete but this can mean many things (like not
> available to license).
> 
> I'll try to see if any of the A8 past product managers know anything
> about this. In the meantime, I would leave them in (no run-time
> overhead).

FWIW, I just fired up a RealView PB-A8 board to check, and that reports
r1p1. True, it's not strictly a real silicon implementation (I think
it's one of the structured ASIC test chips), but since it was, as far as
I'm aware, a commercially-available development system, it's not
impossible that someone may still own and use one of these beasts.

Robin.