From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Thomas Gleixner <tglx@linutronix.de>,
Serge Semin <fancer.lancer@gmail.com>,
Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>,
Paul Burton <paulburton@kernel.org>,
Ralf Baechle <ralf@linux-mips.org>,
Alessandro Zummo <a.zummo@towertech.it>,
Alexandre Belloni <alexandre.belloni@bootlin.com>,
Arnd Bergmann <arnd@arndb.de>, Rob Herring <robh+dt@kernel.org>,
linux-mips@vger.kernel.org, linux-rtc@vger.kernel.org,
devicetree@vger.kernel.org,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 7/7] clocksource: mips-gic-timer: Set limitations on clocksource/sched-clocks usage
Date: Fri, 15 May 2020 19:10:04 +0200 [thread overview]
Message-ID: <20200515171004.GA760381@linaro.org> (raw)
In-Reply-To: <20200506214107.25956-8-Sergey.Semin@baikalelectronics.ru>
On Thu, May 07, 2020 at 12:41:07AM +0300, Serge Semin wrote:
> Currently neither clocksource nor scheduler clock kernel framework
> support the clocks with variable frequency. Needless to say how many
> problems may cause the sudden base clocks frequency change. In a
> simplest case the system time will either slow down or speed up.
> Since on CM2.5 and earlier MIPS GIC timer is synchronously clocked
> with CPU we must set some limitations on using it for these frameworks
> if CPU frequency may change. First of all it's not safe to have the
> MIPS GIC used for scheduler timings. So we shouldn't proceed with
> the clocks registration in the sched-subsystem. Secondly we must
> significantly decrease the MIPS GIC clocksource rating. This will let
> the system to use it only as a last resort.
>
> Note CM3.x-based systems may also experience the problems with MIPS GIC
> if the CPU-frequency change is activated for the whole CPU cluster
> instead of using the individual CPC core clocks divider.
May be there is no alternative but the code looks a bit hacksih. Isn't possible
to do something with the sched_mark_unstable?
Or just not use the timer at all ?
next prev parent reply other threads:[~2020-05-15 17:10 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-06 12:56 [PATCH 0/4] clocksource: Fix MIPS GIC and DW APB Timer for Baikal-T1 SoC support Sergey.Semin
2020-03-24 17:43 ` [PATCH v2 0/6] " Sergey.Semin
2020-03-24 17:43 ` [PATCH v2 1/6] dt-bindings: rtc: Convert snps,dw-apb-timer to DT schema Sergey.Semin
2020-03-24 18:07 ` Alexandre Belloni
2020-03-24 18:20 ` Serge Semin
2020-03-31 20:14 ` Rob Herring
2020-03-24 17:43 ` [PATCH v2 2/6] dt-bindings: interrupt-controller: Convert mti,gic " Sergey.Semin
2020-03-31 21:02 ` Rob Herring
2020-04-01 10:19 ` Sergey Semin
2020-04-01 14:13 ` Rob Herring
2020-04-01 22:07 ` Sergey Semin
2020-03-24 17:43 ` [PATCH v2 3/6] clocksource: dw_apb_timer: Set clockevent any-possible-CPU mask Sergey.Semin
2020-03-24 17:43 ` [PATCH v2 4/6] clocksource: dw_apb_timer_of: Fix missing clockevent timers Sergey.Semin
2020-03-24 17:43 ` [PATCH v2 5/6] clocksource: mips-gic-timer: Register as sched_clock Sergey.Semin
2020-03-24 17:43 ` [PATCH v2 6/6] clocksource: mips-gic-timer: Set limitations on clocksource/sched-clocks usage Sergey.Semin
2020-05-06 21:41 ` [PATCH v3 0/7] clocksource: Fix MIPS GIC and DW APB Timer for Baikal-T1 SoC support Serge Semin
2020-05-06 21:41 ` [PATCH v3 1/7] dt-bindings: rtc: Convert snps,dw-apb-timer to DT schema Serge Semin
2020-05-06 21:41 ` [PATCH v3 2/7] dt-bindings: timer: Move snps,dw-apb-timer DT schema from rtc Serge Semin
2020-05-07 12:03 ` Alexandre Belloni
2020-05-14 19:04 ` Rob Herring
2020-05-06 21:41 ` [PATCH v3 3/7] dt-bindings: interrupt-controller: Convert mti,gic to DT schema Serge Semin
2020-05-14 19:06 ` Rob Herring
2020-05-18 14:51 ` Serge Semin
2020-05-06 21:41 ` [PATCH v3 4/7] clocksource: dw_apb_timer: Set clockevent any-possible-CPU mask Serge Semin
2020-05-06 21:41 ` [PATCH v3 5/7] clocksource: dw_apb_timer_of: Fix missing clockevent timers Serge Semin
2020-05-06 21:41 ` [PATCH v3 6/7] clocksource: mips-gic-timer: Register as sched_clock Serge Semin
2020-05-06 21:41 ` [PATCH v3 7/7] clocksource: mips-gic-timer: Set limitations on clocksource/sched-clocks usage Serge Semin
2020-05-15 17:10 ` Daniel Lezcano [this message]
2020-05-16 12:16 ` Serge Semin
2020-05-18 13:59 ` Daniel Lezcano
2020-05-18 14:40 ` Serge Semin
2020-05-18 14:45 ` Serge Semin
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