From: cov@codeaurora.org (Christopher Covington)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 2/3] ARM: sched_clock: support 64-bit counters
Date: Thu, 21 Mar 2013 10:02:57 -0400 [thread overview]
Message-ID: <514B1311.20308@codeaurora.org> (raw)
In-Reply-To: <1363055197-17296-3-git-send-email-robherring2@gmail.com>
Hi Rob,
On 03/11/2013 10:26 PM, Rob Herring wrote:
> From: Rob Herring <rob.herring@calxeda.com>
>
> With architected timers, we now have 64-bit counters which can be used
> directly for sched_clock. However, the ARM sched_clock code currently just
> uses the lower 32-bits and handles wrapping in software. Add support for
> using the full 64-bit counter values. If multiple counters are registered,
> a 64-bit counter is preferred.
To be more precise, architected timers are anywhere between 56 and 64 bits
wide, zero-extended to 64-bits. See section B8.1.1 of the ARM ARM rev C.b. I
don't know if the code really needs to change until someone has a need to
distinguish more finely between timers, but if you're using access size as an
approximation for counter width, I feel like it at least deserves a mention in
the comments.
[...]
Regards,
Christopher
--
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by
the Linux Foundation
next prev parent reply other threads:[~2013-03-21 14:02 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-12 2:26 [PATCH 0/3] ARM sched_clock selection enhancements Rob Herring
2013-03-12 2:26 ` [PATCH 1/3] ARM: sched_clock: allow changing to higher frequency counter Rob Herring
2013-03-12 2:26 ` [PATCH 2/3] ARM: sched_clock: support 64-bit counters Rob Herring
2013-03-21 14:02 ` Christopher Covington [this message]
2013-03-21 22:15 ` Rob Herring
2013-03-22 12:03 ` Christopher Covington
2013-03-22 12:58 ` Rob Herring
2013-03-22 15:20 ` Russell King - ARM Linux
2013-03-22 11:09 ` Russell King - ARM Linux
2013-03-12 2:26 ` [PATCH 3/3] ARM: arch_timer: use the 64-bit sched_clock setup Rob Herring
2013-03-12 9:23 ` [PATCH 0/3] ARM sched_clock selection enhancements Russell King - ARM Linux
2013-03-12 12:43 ` Rob Herring
2013-03-20 23:03 ` Rob Herring
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