[PATCH] arm: dts: exynos5: Remove multi core timer

[Doug Anderson]

Tomasz,

On Thu, May 15, 2014 at 3:13 PM, Tomasz Figa <tomasz.figa at gmail.com> wrote:
>> NOTE: if for some reason we need to keep the MCT around, we're
>> definitely going to need to account for the fact that tweaking it
>> affects the arch timer.  ...and having the arch timer is really nice
>> since:
>
> [Let me reorder the points below to make it easier to comment:]
>
>> * it's faster to access.
>> * it is accessible from userspace for really fast access.
>
> Do you have some data on whether it is a significant difference,
> especially considering real use cases?

I know that Chrome makes _a lot_ of calls to gettimeofday() for
profiling purposes, enough that it showed up on benchmarks.  In fact,
we made a change to the MCT to make accesses faster and there's a
small mention of the benchmarking that was done at:

https://chromium-review.googlesource.com/#/c/32190/

...that change probably should be sent upstream, actually.

I'll let Chirantan comment on how much faster arch timers were.
...and I think David Riley (also CCed now) may be able to comment on
the benefits of userspace timers.


>> * it implements the bits needed for udelay() to use it.
>
> Hmm, do you know what bits are those? On Exynos4 MCT is the only option
> and it would be nice to let udelay() use it.

Look for register_current_timer_delay().  It seems like we could do
this for MCT, but I've never done the investigation because we were
always planning to move to arch timers.  ;)

-Doug