[PATCH 6/6] aarch64: Add hp-timing.h

[Marcus Shawcroft]

> On Mon, Jul 21, 2014 at 12:05 PM, Richard Henderson <rth@twiddle.net> wrote:

> Do you know of any real hardware that doesn't have the timers?  I really can't
> imagine them being elided.

I'd like to see the generic timers none optional in cortex-a class
processors, however they are currently, unfortunately, defined as
optional. The design choices made in the first few instances of armv8
hardware are not necessarily a good basis for predicting the variety
of design choices that will follow in subsequent implementations.

> On 21 July 2014 21:42, Andrew Pinski <pinskia@gmail.com> wrote:

> More than that, right now the Linux kernel requires the timings so it
> is not optional for the linux kernel.
> http://lists.infradead.org/pipermail/linux-arm-kernel/2012-August/114155.html
>
> That patch makes it sound like it is part of the kernel userland
> ABI/API as it allows for a fast gettimeofday() (that does not have to
> be in VDSO if I read the comment correctly).

The counter is for the benefit of the VDSO in order for the VDSO to
provide a fast gettimeofday on systems where the counter is present.

Cheers
/Marcus