[PATCH 2/3] ARM: sched_clock: support 64-bit counters

Christopher Covington cov at codeaurora.org
Thu Mar 21 10:02:57 EDT 2013

Hi Rob,

On 03/11/2013 10:26 PM, Rob Herring wrote:
> From: Rob Herring <rob.herring at 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.



Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by
the Linux Foundation

More information about the linux-arm-kernel mailing list