From: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
To: Alex Smith <alex@alex-smith.me.uk>
Cc: David Daney <ddaney.cavm@gmail.com>,
Ralf Baechle <ralf@linux-mips.org>,
Markos Chandras <markos.chandras@imgtec.com>,
linux-mips <linux-mips@linux-mips.org>,
Alex Smith <alex.smith@imgtec.com>,
<linux-kernel@vger.kernel.org>
Subject: Re: [v3, 3/3] MIPS: VDSO: Add implementations of gettimeofday() and clock_gettime()
Date: Wed, 28 Oct 2015 12:28:21 -0700 [thread overview]
Message-ID: <563121D5.4030601@imgtec.com> (raw)
In-Reply-To: <CAOFt0_AvGQcxHAToEevTFt5JGiuhN03XnPxxjQizbZ3dC-06mg@mail.gmail.com>
On 10/28/2015 12:04 PM, Alex Smith wrote:
> On 28 October 2015 at 18:57, Leonid Yegoshin <Leonid.Yegoshin@imgtec.com> wrote:
>>
> As I've explained the VDSO will only use the CP0 counter in the same
> situations that the kernel would when it is the active clocksource.
> Any issue that makes the counter unreliable affects the kernel as well
> and is unrelated to the VDSO, so a fix does not belong in this patch.
What would you do if some SoC with different type of cores will define
CPU1 etc CP0_COUNT as a DIFFERENT clocksource from CPU0 (because of
frequency etc)? Timekeeping can select CPU0 clocksource but code still
uses a local CPU1 CP0_COUNT for gettimeofday().
And this kind of solution is the first in line to have an accurate
timing in systems without GIC and with different clock frequencies.
- Leonid
WARNING: multiple messages have this Message-ID (diff)
From: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
To: Alex Smith <alex@alex-smith.me.uk>
Cc: David Daney <ddaney.cavm@gmail.com>,
Ralf Baechle <ralf@linux-mips.org>,
Markos Chandras <markos.chandras@imgtec.com>,
linux-mips <linux-mips@linux-mips.org>,
Alex Smith <alex.smith@imgtec.com>,
linux-kernel@vger.kernel.org
Subject: Re: [v3, 3/3] MIPS: VDSO: Add implementations of gettimeofday() and clock_gettime()
Date: Wed, 28 Oct 2015 12:28:21 -0700 [thread overview]
Message-ID: <563121D5.4030601@imgtec.com> (raw)
Message-ID: <20151028192821.eEPmBcVjzjZVUzNIpNDCYcDOAU3iytxzYwps8yaAf1g@z> (raw)
In-Reply-To: <CAOFt0_AvGQcxHAToEevTFt5JGiuhN03XnPxxjQizbZ3dC-06mg@mail.gmail.com>
On 10/28/2015 12:04 PM, Alex Smith wrote:
> On 28 October 2015 at 18:57, Leonid Yegoshin <Leonid.Yegoshin@imgtec.com> wrote:
>>
> As I've explained the VDSO will only use the CP0 counter in the same
> situations that the kernel would when it is the active clocksource.
> Any issue that makes the counter unreliable affects the kernel as well
> and is unrelated to the VDSO, so a fix does not belong in this patch.
What would you do if some SoC with different type of cores will define
CPU1 etc CP0_COUNT as a DIFFERENT clocksource from CPU0 (because of
frequency etc)? Timekeeping can select CPU0 clocksource but code still
uses a local CPU1 CP0_COUNT for gettimeofday().
And this kind of solution is the first in line to have an accurate
timing in systems without GIC and with different clock frequencies.
- Leonid
next prev parent reply other threads:[~2015-10-28 19:28 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-28 10:03 [PATCH 0/3] MIPS VDSO support Markos Chandras
2015-09-28 10:03 ` Markos Chandras
2015-09-28 10:10 ` [PATCH 1/3] MIPS: Initial implementation of a VDSO Markos Chandras
2015-09-28 10:10 ` Markos Chandras
2015-09-28 10:54 ` Alex Smith
2015-09-28 13:07 ` Matthew Fortune
2015-09-28 13:07 ` Matthew Fortune
2015-11-20 18:15 ` Maciej W. Rozycki
2015-10-09 8:05 ` [PATCH v2 " Markos Chandras
2015-10-09 8:05 ` Markos Chandras
2015-10-21 8:54 ` [PATCH v3 " Markos Chandras
2015-10-21 8:54 ` Markos Chandras
2015-09-28 10:11 ` [PATCH 2/3] irqchip: irq-mips-gic: Provide function to map GIC user section Markos Chandras
2015-09-28 10:11 ` Markos Chandras
2015-09-28 10:55 ` Marc Zyngier
2015-09-28 14:16 ` Qais Yousef
2015-09-28 14:16 ` Qais Yousef
2015-09-28 15:03 ` Marc Zyngier
2015-10-05 8:22 ` Markos Chandras
2015-10-05 8:22 ` Markos Chandras
2015-10-12 9:40 ` [PATCH v2 " Markos Chandras
2015-10-12 9:40 ` Markos Chandras
2015-10-12 9:51 ` Marc Zyngier
2015-10-12 10:16 ` Thomas Gleixner
2015-10-15 9:37 ` Qais Yousef
2015-10-15 9:37 ` Qais Yousef
2015-10-15 10:18 ` Thomas Gleixner
2015-09-28 10:12 ` [PATCH 3/3] MIPS: VDSO: Add implementations of gettimeofday() and clock_gettime() Markos Chandras
2015-09-28 10:12 ` Markos Chandras
2015-09-28 13:15 ` kbuild test robot
2015-09-28 13:15 ` kbuild test robot
2015-10-12 10:24 ` [PATCH v2 " Markos Chandras
2015-10-12 10:24 ` Markos Chandras
2015-10-21 8:57 ` [PATCH v3 " Markos Chandras
2015-10-21 8:57 ` Markos Chandras
2015-10-23 1:41 ` [v3, " Leonid Yegoshin
2015-10-23 1:41 ` Leonid Yegoshin
2015-10-27 14:47 ` Ralf Baechle
2015-10-27 20:46 ` Leonid Yegoshin
2015-10-27 20:46 ` Leonid Yegoshin
2015-10-27 21:02 ` David Daney
2015-10-27 21:15 ` Leonid Yegoshin
2015-10-27 21:15 ` Leonid Yegoshin
2015-10-27 21:44 ` David Daney
2015-10-27 21:49 ` Leonid Yegoshin
2015-10-27 21:49 ` Leonid Yegoshin
2015-10-28 10:20 ` Alex Smith
2015-10-28 18:21 ` Leonid Yegoshin
2015-10-28 18:21 ` Leonid Yegoshin
2015-10-28 18:30 ` Alex Smith
2015-10-28 18:57 ` Leonid Yegoshin
2015-10-28 18:57 ` Leonid Yegoshin
2015-10-28 19:04 ` Alex Smith
2015-10-28 19:28 ` Leonid Yegoshin [this message]
2015-10-28 19:28 ` Leonid Yegoshin
2015-10-28 19:55 ` Alex Smith
2015-10-28 20:15 ` Leonid Yegoshin
2015-10-28 20:15 ` Leonid Yegoshin
2016-01-25 22:36 ` [PATCH v3 " Hauke Mehrtens
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