linux-kernel - Re: [RFC PATCH 00/10] Add persistent clock support

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Date:   Wed, 16 May 2018 15:11:48 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Tony Lindgren <tony@...mide.com>, aaro.koskinen@....fi,
        linux@...linux.org.uk, Mark Rutland <mark.rutland@....com>,
        Marc Zyngier <marc.zyngier@....com>,
        Mark Brown <broonie@...nel.org>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        mlichvar@...hat.com, rdunlap@...radead.org,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jon Hunter <jonathanh@...dia.com>,
        Heiko Stübner <heiko@...ech.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, peterz@...radead.org,
        douly.fnst@...fujitsu.com, len.brown@...el.com,
        rajvi.jingar@...el.com,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        x86@...nel.org, Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-tegra@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        linux-omap@...r.kernel.org
Subject: Re: [RFC PATCH 00/10] Add persistent clock support

On 16 May 2018 at 10:20, Baolin Wang <baolin.wang@...aro.org> wrote:
> Hi Daniel,
>
> On 15 May 2018 at 18:27, Daniel Lezcano <daniel.lezcano@...aro.org> wrote:
>> On Mon, May 14, 2018 at 04:55:26PM +0800, Baolin Wang wrote:
>>> Hi,
>>>
>>> We will meet below issues when compensating the suspend time for the timekeeping.
>>>
>>> 1. We have too many different ways of dealing with persistent timekeeping
>>> across architectures, so it is hard for one driver to compatable with different
>>> architectures.
>>>
>>> 2. On some platforms (such as Spreadtrum platform), we registered the high
>>> resolution timer as one clocksource to update the OS time, but the high
>>> resolution timer will be stopped in suspend state. So we use another one
>>> always-on timer (but low resolution) to calculate the suspend time to
>>> compensate the OS time. Though we can register the always-on timer as one
>>> clocksource, we need re-calculate the mult/shift with one larger conversion
>>> range to calculate the suspend time and need update the clock in case of
>>> running over the always-on timer.
>>
>> First, can you elaborate what you mean by 'suspend state' ? On which power
>
> What I mean is the high resolution timer will be stopped when the
> system goes into suspend state.
>
>> domain the clocksource belongs to?
>
> On Spreadtrum platform, It belongs to one power domain named
> "APCPU_TOP", that will be power down when the system goes into suspend
> state.

Sorry, I made a mistake here. Our high resolution timer is on one
always-on power domain, but it's clock will be shut down when the
system goes into suspend.

-- 
Baolin.wang
Best Regards