linux-kernel - Re: [PATCH 1/2] time: Introduce one suspend clocksource to compensate the suspend time

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Message-ID: <alpine.DEB.2.21.1807171039220.1740@nanos.tec.linutronix.de>
Date:   Tue, 17 Jul 2018 10:40:12 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Baolin Wang <baolin.wang@...aro.org>
cc:     john.stultz@...aro.org, sboyd@...nel.org, arnd@...db.de,
        broonie@...nel.org, daniel.lezcano@...aro.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] time: Introduce one suspend clocksource to compensate
 the suspend time

On Tue, 17 Jul 2018, Baolin Wang wrote:
> On some hardware with multiple clocksources, we have coarse grained
> clocksources that support the CLOCK_SOURCE_SUSPEND_NONSTOP flag, but
> which are less than ideal for timekeeping whereas other clocksources
> can be better candidates but halt on suspend.
> 
> Currently, the timekeeping core only supports timing suspend using
> CLOCK_SOURCE_SUSPEND_NONSTOP clocksources if that clocksource is the
> current clocksource for timekeeping.
> 
> As a result, some architectures try to implement read_persistent_clock64()
> using those non-stop clocksources, but isn't really ideal, which will
> introduce more duplicate code. To fix this, provide logic to allow a
> registered SUSPEND_NONSTOP clocksource, which isn't the current
> clocksource, to be used to calculate the suspend time.
> 
> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>

Well done!

Reviewed-by: Thomas Gleixner <tglx@...utronix.de>