linux-kernel - [PATCH 0/2] Quiet power limit notification

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Date:	Wed, 15 May 2013 06:36:55 -0700
From:	"Fenghua Yu" <fenghua.yu@...el.com>
To:	"Rafael Wysocki" <rafal.j.wysocki@...el.com>,
	"Len Brown" <len.brown@...el.com>
Cc:	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"x86" <x86@...nel.org>, "linux-pm" <linux-pm@...r.kernel.org>,
	"Fenghua Yu" <fenghua.yu@...el.com>
Subject: [PATCH 0/2]  Quiet power limit notification

From: Fenghua Yu <fenghua.yu@...el.com>

Power Limit Notification (X86_FEATURE_PLN) was added in Sandy Bridge
to give the OS the option of knowing when the package has reached
a configured power threshold.

Linux-2.6.36 enabled this feature:
0199114c31798af5b83841b21759b64171060d9b
(x86, hwmon: Package Level Thermal/Power: power limit)

It enabld the interrupt, and the interrupt hander
added to the MCE log and printed to the console:

printk(KERN_CRIT "CPU%d: %s power limit notification (total events = %lu)
printk(KERN_INFO "CPU%d: %s power limit normal\n"

However, these events are quite routine on some systems under some conditions,
alarming customers and provoking un-necessary customer support calls.

So the MCE log entry was deleted in Linux-3.3:

29e9bf1841e4f9df13b4992a716fece7087dd237
(x86, mce, therm_throt: Don't report power limit and package level thermal throttle events in mcelog)

Here we delete the corresponding kernel console messages,
and then we disable the interrupt by default -- allowing it
to be enabled by cmdline for diagnosis purposes.

https://bugzilla.kernel.org/show_bug.cgi?id=36182

This pair of patches applies cleanly back to Linux-3.3.

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