linux-kernel - Re: [PATCH] clocksource/arm_global_timer: reconfigure clockevents after cpufreq change

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Message-Id: <2F6A5074-F54E-4B16-AB3D-DE7301E363FC@gmail.com>
Date:   Tue, 29 Nov 2016 17:05:19 +0300
From:   Alexander Kochetkov <al.kochet@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        LAK <linux-arm-kernel@...ts.infradead.org>, kernel@...inux.com,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Patrice Chotard <patrice.chotard@...com>,
        Marc Zyngier <marc.zyngier@....com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] clocksource/arm_global_timer: reconfigure clockevents after cpufreq change

Hello Thomas!

> 29 нояб. 2016 г., в 16:42, Thomas Gleixner <tglx@...utronix.de> написал(а):
> 
> The frequency change would not only affect the clockevent device, it also
> would affect the clocksource. So the patch is incomplete, but see below.
Looks like kernel disallow change clocksource and shed_clock rate at
runtime. I haven’t found any function for that.

> 29 нояб. 2016 г., в 16:42, Thomas Gleixner <tglx@...utronix.de> написал(а):
> 
> That's broken and the clk framework should keep the CORE_PERI clock at a
> constant rate by reprogramming the divider of the CPU clock.

Thank you for the hint.

> Assumptions w/o real impact are a perfect reason not to apply that
> patch. This want's a proper proof that the global timer really changes and
> this hackery is required, which I seriously doubt.

It really changes. It changes like it changes for smp-twd. I guess they are
driven by same clock CORE_PERI.

Thank you for help.

Alexander.