From: Will Deacon <will.deacon@arm.com>
To: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: catalin.marinas@arm.com, mark.rutland@arm.com,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, steve.capper@linaro.org,
stuart.monteith@linaro.org
Subject: Re: [PATCH v8] arm64: cpuinfo: Expose MIDR_EL1 and REVIDR_EL1 to sysfs
Date: Tue, 5 Jul 2016 15:56:31 +0100 [thread overview]
Message-ID: <20160705145631.GB28482@arm.com> (raw)
In-Reply-To: <1467624020-29240-1-git-send-email-suzuki.poulose@arm.com>
On Mon, Jul 04, 2016 at 10:20:20AM +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 code generation.
>
> This patch exposes these registers through sysfs:
>
> /sys/devices/system/cpu/cpu$ID/regs/identification/midr_el1
> /sys/devices/system/cpu/cpu$ID/regs/identification/revidr_el1
>
> 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.
[...]
> +static int cpuid_add_regs(int cpu)
> +{
> + int rc;
> + struct device *dev;
> + struct cpuinfo_arm64 *info = &per_cpu(cpu_data, cpu);
> +
> + dev = get_cpu_device(cpu);
> + if (dev) {
> + rc = kobject_add(&info->kobj, &dev->kobj, "regs");
> + if (!rc)
> + rc = sysfs_create_group(&info->kobj, &cpuregs_attr_group);
If this call fails...
> + } else {
> + return -ENODEV;
> + }
> +
> + return rc;
> +}
> +
> +static int cpuid_remove_regs(int cpu)
> +{
> + int rc = 0;
> + struct device *dev;
> + struct cpuinfo_arm64 *info = &per_cpu(cpu_data, cpu);
> +
> + dev = get_cpu_device(cpu);
> + if (dev) {
> + sysfs_remove_group(&info->kobj, &cpuregs_attr_group);
... then we still call sysfs_remove_group on the CPU_DEAD path. I think
that just results in a WARN, but it would be good to double-check this
(perhaps by forcing the failure path).
Will
prev parent reply other threads:[~2016-07-05 14:56 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-04 9:20 [PATCH v8] arm64: cpuinfo: Expose MIDR_EL1 and REVIDR_EL1 to sysfs Suzuki K Poulose
2016-07-05 14:56 ` Will Deacon [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160705145631.GB28482@arm.com \
--to=will.deacon@arm.com \
--cc=catalin.marinas@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=steve.capper@linaro.org \
--cc=stuart.monteith@linaro.org \
--cc=suzuki.poulose@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox