Re: [PATCH v4] arm64: cpuinfo: Expose MIDR_EL1 and REVIDR_EL1 to sysfs

Russell King - ARM Linux
2016-06-13T17:21:50Z

On Mon, Jun 13, 2016 at 06:08:09PM +0100, Suzuki K Poulose wrote:
> From: Steve Capper <steve.capper@linaro.org>
>
> It can be useful for JIT software to be aware of MIDR_EL1 and
> REVIDR_EL1 to ascertain the presence of any core errata that could
> affect codegen.
>
> This patch exposes these registers through sysfs:
>
> /sys/devices/system/cpu/cpu$ID/identification/midr
> /sys/devices/system/cpu/cpu$ID/identification/revidr
>
> where $ID is the cpu number. For big.LITTLE systems, one can have a
> mixture of cores (e.g. Cortex A53 and Cortex A57), thus all CPUs need
> to be enumerated.
>
> If the kernel does not have valid information to populate these entries
> with, an empty string is returned to userspace.

So there's no confusion, I've historically said no on 32-bit ARM to
exposing the MIDR to userspace, and my position on that for 32-bit
ARM has not changed.

--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.