From: Mason <slash.tmp@free.fr>
To: John Stultz <john.stultz@linaro.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Catalin Marinas <catalin.marinas@arm.com>
Subject: Re: High-resolution timers not supported when using smp_twd
Date: Fri, 01 May 2015 10:17:02 +0200 [thread overview]
Message-ID: <5543367E.5040807@free.fr> (raw)
In-Reply-To: <CALAqxLW-2knOPUpvWHS4YNgx+me492gtf+N+g6+=vB57XNSfOQ@mail.gmail.com>
Hello John,
On 30/04/2015 18:42, John Stultz wrote:
> On Thu, Apr 30, 2015 at 5:46 AM, Mason wrote:
>
>> I wanted to enable high-resolution timers on this Cortex A9 system,
>> but it seems there is more to it than just enabling
>>
>> CONFIG_HIGH_RES_TIMERS=y
>>
>> (The system is limited to jiffy resolution.)
>
> You might make sure you've got a HRT enabled clocksource installed?
>
> You might check
> /sys/devices/system/clocksource/clocksource0/current_clocksource ?
Thanks for the suggestion, I will check on Monday.
The clocksource is a constant 27 MHz 32-bit counter.
It seems the problem comes from the clockevent source, which is
marked CLOCK_EVT_FEAT_C3STOP. If I remove that flag, then hrtimers
are enabled; but the flag is there for a good reason, I assume.
I will resend my message to the LAKML on Monday.
Regards.
prev parent reply other threads:[~2015-05-01 8:17 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-30 12:46 High-resolution timers not supported when using smp_twd Mason
2015-04-30 16:42 ` John Stultz
2015-05-01 8:17 ` Mason [this message]
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