From: Valentin Schneider <valentin.schneider@arm.com>
To: Lukasz Luba <lukasz.luba@arm.com>, Marc Zyngier <maz@kernel.org>
Cc: Ionela Voinescu <ionela.voinescu@arm.com>,
catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com,
suzuki.poulose@arm.com, sudeep.holla@arm.com, rjw@rjwysocki.net,
peterz@infradead.org, mingo@redhat.com,
vincent.guittot@linaro.org, viresh.kumar@linaro.org,
linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH v3 7/7] clocksource/drivers/arm_arch_timer: validate arch_timer_rate
Date: Wed, 12 Feb 2020 11:12:33 +0000 [thread overview]
Message-ID: <eeafe486-e408-b229-24ef-329649a13f70@arm.com> (raw)
In-Reply-To: <289c6110-b7ea-1d61-d795-551723263803@arm.com>
On 12/02/2020 10:55, Lukasz Luba wrote:
>> Because, as the commit message outlines it, such a frequency is terribly
>> out of spec?
>
> I don't see in the RM that < 1MHz is terribly out of spec.
> 'Frequency
> Increments at a fixed frequency, typically in the range 1-50MHz.
> Can support one or more alternative operating modes in which it increments by larger amounts at a
> lower frequency, typically for power-saving.'
>
> There is even an example how to operate at 20kHz and increment by 500.
>
> I don't know the code if it's supported, thought.
>
For that one case the value reported by CNTFRQ shouldn't change - it's still
a timer that looks like is operating at 10MHz, but under the hood is doing
bigger increments at lower freq.
As I was trying to get to, this patch isn't validating the actual frequency
the timer operates on, rather that whatever is reported by CNTFRQ is
somewhat sane (which here means [1, 50]MHz, although we just check the
lower bound).
[...]
>> And? It seems to address a potential issue where the time frequency
>> is out of spec, and makes sure we don't end up with additional problems
>> in the AMU code.
>
> This patch just prints warning, does not change anything in booting or
> in any code related to AMU.
>
Right, but it should still be worth having - at least it shows up in
dmesg, and when someone reports something fishy we get a hint that we can
blame the hardware.
>>
>> On its own, it is perfectly sensible and could be merged as part of this
>> series with my
>>
>> Acked-by: Marc Zyngier <maz@kernel.org>
>>
>> M.
>
> Regards,
> Lukasz
WARNING: multiple messages have this Message-ID (diff)
From: Valentin Schneider <valentin.schneider@arm.com>
To: Lukasz Luba <lukasz.luba@arm.com>, Marc Zyngier <maz@kernel.org>
Cc: mark.rutland@arm.com, will@kernel.org, suzuki.poulose@arm.com,
peterz@infradead.org, catalin.marinas@arm.com,
linux-pm@vger.kernel.org, linux-doc@vger.kernel.org,
rjw@rjwysocki.net, linux-kernel@vger.kernel.org,
mingo@redhat.com, viresh.kumar@linaro.org, sudeep.holla@arm.com,
Ionela Voinescu <ionela.voinescu@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 7/7] clocksource/drivers/arm_arch_timer: validate arch_timer_rate
Date: Wed, 12 Feb 2020 11:12:33 +0000 [thread overview]
Message-ID: <eeafe486-e408-b229-24ef-329649a13f70@arm.com> (raw)
In-Reply-To: <289c6110-b7ea-1d61-d795-551723263803@arm.com>
On 12/02/2020 10:55, Lukasz Luba wrote:
>> Because, as the commit message outlines it, such a frequency is terribly
>> out of spec?
>
> I don't see in the RM that < 1MHz is terribly out of spec.
> 'Frequency
> Increments at a fixed frequency, typically in the range 1-50MHz.
> Can support one or more alternative operating modes in which it increments by larger amounts at a
> lower frequency, typically for power-saving.'
>
> There is even an example how to operate at 20kHz and increment by 500.
>
> I don't know the code if it's supported, thought.
>
For that one case the value reported by CNTFRQ shouldn't change - it's still
a timer that looks like is operating at 10MHz, but under the hood is doing
bigger increments at lower freq.
As I was trying to get to, this patch isn't validating the actual frequency
the timer operates on, rather that whatever is reported by CNTFRQ is
somewhat sane (which here means [1, 50]MHz, although we just check the
lower bound).
[...]
>> And? It seems to address a potential issue where the time frequency
>> is out of spec, and makes sure we don't end up with additional problems
>> in the AMU code.
>
> This patch just prints warning, does not change anything in booting or
> in any code related to AMU.
>
Right, but it should still be worth having - at least it shows up in
dmesg, and when someone reports something fishy we get a hint that we can
blame the hardware.
>>
>> On its own, it is perfectly sensible and could be merged as part of this
>> series with my
>>
>> Acked-by: Marc Zyngier <maz@kernel.org>
>>
>> M.
>
> Regards,
> Lukasz
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next prev parent reply other threads:[~2020-02-12 11:12 UTC|newest]
Thread overview: 84+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-11 18:45 [PATCH v3 0/7] arm64: ARMv8.4 Activity Monitors support Ionela Voinescu
2020-02-11 18:45 ` Ionela Voinescu
2020-02-11 18:45 ` [PATCH v3 1/7] arm64: add support for the AMU extension v1 Ionela Voinescu
2020-02-11 18:45 ` Ionela Voinescu
2020-02-12 11:30 ` Suzuki Kuruppassery Poulose
2020-02-12 11:30 ` Suzuki Kuruppassery Poulose
2020-02-12 14:54 ` Valentin Schneider
2020-02-12 14:54 ` Valentin Schneider
2020-02-12 16:10 ` Ionela Voinescu
2020-02-12 16:10 ` Ionela Voinescu
2020-02-12 16:20 ` Suzuki Kuruppassery Poulose
2020-02-12 16:20 ` Suzuki Kuruppassery Poulose
2020-02-12 18:20 ` Ionela Voinescu
2020-02-12 18:20 ` Ionela Voinescu
2020-02-12 19:24 ` Suzuki K Poulose
2020-02-12 19:24 ` Suzuki K Poulose
2020-02-12 20:19 ` Ionela Voinescu
2020-02-12 20:19 ` Ionela Voinescu
2020-02-12 16:24 ` Vladimir Murzin
2020-02-12 16:24 ` Vladimir Murzin
2020-02-12 18:27 ` Ionela Voinescu
2020-02-12 18:27 ` Ionela Voinescu
2020-02-11 18:45 ` [PATCH v3 2/7] arm64: trap to EL1 accesses to AMU counters from EL0 Ionela Voinescu
2020-02-11 18:45 ` Ionela Voinescu
2020-02-12 11:44 ` Suzuki Kuruppassery Poulose
2020-02-12 11:44 ` Suzuki Kuruppassery Poulose
2020-02-12 15:36 ` Valentin Schneider
2020-02-12 15:36 ` Valentin Schneider
2020-02-11 18:45 ` [PATCH v3 3/7] arm64/kvm: disable access to AMU registers from kvm guests Ionela Voinescu
2020-02-11 18:45 ` Ionela Voinescu
2020-02-12 15:36 ` Valentin Schneider
2020-02-12 15:36 ` Valentin Schneider
2020-02-12 16:33 ` Suzuki Kuruppassery Poulose
2020-02-12 16:33 ` Suzuki Kuruppassery Poulose
2020-02-11 18:45 ` [PATCH v3 4/7] Documentation: arm64: document support for the AMU extension Ionela Voinescu
2020-02-11 18:45 ` Ionela Voinescu
2020-02-12 15:36 ` Valentin Schneider
2020-02-12 15:36 ` Valentin Schneider
2020-02-11 18:45 ` [PATCH v3 5/7] cpufreq: add function to get the hardware max frequency Ionela Voinescu
2020-02-11 18:45 ` Ionela Voinescu
2020-02-12 4:14 ` Viresh Kumar
2020-02-12 4:14 ` Viresh Kumar
2020-02-13 11:59 ` Valentin Schneider
2020-02-13 11:59 ` Valentin Schneider
2020-02-13 12:59 ` Ionela Voinescu
2020-02-13 12:59 ` Ionela Voinescu
2020-02-13 15:22 ` Valentin Schneider
2020-02-13 15:22 ` Valentin Schneider
2020-02-11 18:45 ` [PATCH v3 6/7] arm64: use activity monitors for frequency invariance Ionela Voinescu
2020-02-11 18:45 ` Ionela Voinescu
2020-02-12 18:59 ` Lukasz Luba
2020-02-12 18:59 ` Lukasz Luba
2020-02-13 9:47 ` Ionela Voinescu
2020-02-13 9:47 ` Ionela Voinescu
2020-02-17 16:59 ` Valentin Schneider
2020-02-17 16:59 ` Valentin Schneider
2020-02-23 18:49 ` Ionela Voinescu
2020-02-23 18:49 ` Ionela Voinescu
2020-02-11 18:45 ` [PATCH v3 7/7] clocksource/drivers/arm_arch_timer: validate arch_timer_rate Ionela Voinescu
2020-02-11 18:45 ` Ionela Voinescu
2020-02-12 9:30 ` Valentin Schneider
2020-02-12 9:30 ` Valentin Schneider
2020-02-12 10:32 ` Ionela Voinescu
2020-02-12 10:32 ` Ionela Voinescu
2020-02-12 10:01 ` Lukasz Luba
2020-02-12 10:01 ` Lukasz Luba
2020-02-12 10:12 ` Marc Zyngier
2020-02-12 10:12 ` Marc Zyngier
2020-02-12 10:54 ` Ionela Voinescu
2020-02-12 10:54 ` Ionela Voinescu
2020-02-12 10:55 ` Lukasz Luba
2020-02-12 10:55 ` Lukasz Luba
2020-02-12 11:10 ` Marc Zyngier
2020-02-12 11:10 ` Marc Zyngier
2020-02-12 11:43 ` Lukasz Luba
2020-02-12 11:43 ` Lukasz Luba
2020-02-12 11:12 ` Valentin Schneider [this message]
2020-02-12 11:12 ` Valentin Schneider
2020-02-14 0:35 ` Thomas Gleixner
2020-02-14 0:35 ` Thomas Gleixner
2020-02-14 15:45 ` Ionela Voinescu
2020-02-14 15:45 ` Ionela Voinescu
2020-02-14 15:57 ` Ionela Voinescu
2020-02-14 15:57 ` Ionela Voinescu
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