From: Nathan_Lynch@mentor•com (Nathan Lynch)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v6 0/6] ARM: vdso gettimeofday using generic timer architecture
Date: Wed, 23 Apr 2014 21:28:33 -0500 [thread overview]
Message-ID: <535876D1.8040609@mentor.com> (raw)
In-Reply-To: <53581865.2020601@codeaurora.org>
On 04/23/2014 02:45 PM, Stephen Boyd wrote:
> On 04/22/14 17:48, Nathan Lynch wrote:
>> Provide fast userspace implementations of gettimeofday and
>> clock_gettime on systems that implement the generic timers extension
>> defined in ARMv7. This follows the example of arm64 in conception but
>> significantly differs in some aspects of the implementation (C vs
>> assembly, mainly).
>>
>> Clocks supported:
>> - CLOCK_REALTIME
>> - CLOCK_MONOTONIC
>> - CLOCK_REALTIME_COARSE
>> - CLOCK_MONOTONIC_COARSE
>>
>> This also provides clock_getres (as arm64 does).
>>
>> Note that while the high-precision realtime and monotonic clock
>> support depends on the generic timers extension, support for
>> clock_getres and coarse clocks is independent of the timer
>> implementation and is provided unconditionally.
>
> I think we'll need to rename the clocksource in arch_timer.c if we only
> have an mmio architected timer to something like arch_mem_counter.
I guess ARMv7 would allow you to have mmio without cp15 (AFAIK ARMv8
does not). I don't see any dts in arch/arm that contains an
arm,armv7-timer-mem node without an arm,armv7-timer node, though.
If this is a practical concern, I think using
CONFIG_ARCH_CLOCKSOURCE_DATA is perhaps a better way to communicate
whether cp15 access is available. That's how the x86 vdso, for example,
decides between using HPET vs TSC etc.
next prev parent reply other threads:[~2014-04-24 2:28 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-23 0:48 [PATCH v6 0/6] ARM: vdso gettimeofday using generic timer architecture Nathan Lynch
2014-04-23 0:48 ` [PATCH v6 1/6] ARM: place sigpage at a random offset above stack Nathan Lynch
2014-04-23 0:48 ` [PATCH v6 2/6] ARM: allow user access to arch timer virtual counter Nathan Lynch
2014-04-23 17:32 ` Will Deacon
2014-04-23 17:41 ` Nathan Lynch
2014-04-24 10:18 ` Will Deacon
2014-04-23 0:48 ` [PATCH v6 3/6] ARM: miscellaneous vdso infrastructure, preparation Nathan Lynch
2014-04-23 0:48 ` [PATCH v6 4/6] ARM: add vdso user-space code Nathan Lynch
2014-04-23 0:48 ` [PATCH v6 5/6] ARM: vdso initialization, mapping, and synchronization Nathan Lynch
2014-04-23 0:48 ` [PATCH v6 6/6] ARM: add CONFIG_VDSO Kconfig and Makefile bits Nathan Lynch
2014-04-23 19:45 ` [PATCH v6 0/6] ARM: vdso gettimeofday using generic timer architecture Stephen Boyd
2014-04-24 2:28 ` Nathan Lynch [this message]
2014-04-24 17:00 ` Stephen Boyd
2014-04-23 21:50 ` Russell King - ARM Linux
2014-04-24 7:37 ` Ard Biesheuvel
2014-04-24 15:15 ` Nathan Lynch
2014-04-24 15:25 ` Ard Biesheuvel
2014-04-24 14:59 ` Nathan Lynch
2014-04-24 16:22 ` Russell King - ARM Linux
2014-04-24 18:41 ` Nathan Lynch
2014-04-24 18:45 ` Russell King - ARM Linux
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