linux-kernel - [PATCH 0/2] cpufreq: intel_pstate: Avoid missing HWP max limit updates with powersave governor

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Message-ID: <1666263.spd1I39WAV@kreacher>
Date:   Thu, 22 Oct 2020 13:55:13 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux PM <linux-pm@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Zhang Rui <rui.zhang@...el.com>
Subject: [PATCH 0/2] cpufreq: intel_pstate: Avoid missing HWP max limit updates with powersave governor

Hi All,

There is a problem in intel_pstate that if it works in the passive mode with
HWP enabled and the "powersave" governor is used on top of it, then changing
the policy max frequency doesn't cause the HWP max limit to be updated which
is quite confusing.

That happens because of two checks, one in the cpufreq core and one in the
driver itself, that are there to avoid unnecessary HW/FW updates when the
current frequency doesn't change.  Of course, that is the case when the
policy max limit changes under the "powersave" governor (which sets the
current frequency to the policy min limit), but in that particular case,
the checks turn out to be harmful.  This is dealt with by the first patch.

The second one is an optimization that can be done right away on top of the
first one.

Thanks!