On 05/17/14 07:56, Chirantan Ekbote wrote:
Anyway, I'm by no means opposed to switching to arch timers. They
provide a well designed, generic interface and drivers shared by
multiple platforms, which means more code sharing and possibly more eyes
looking at the code, which is always good. However if they don't support
low power states correctly, we can't just remove MCT.
I think low power states aren't in mainline (right?).
One solution that might work could be to leave the device tree entry
alone but change the MCT init code to simply act as a no-op if it sees
an arch timer is in the device tree and enabled. Then when/if someone
got the low power states enabled we could just change source code
rather than dts files.
Doug and I were talking about this and we think we may have a way to
have the mct and arch timers co-exist. The main issue is that the mct
(and therefore arch timer) gets cleared once during boot and every
time we do a suspend / resume. This happens in
exynos4_mct_frc_start() but it's not immediately clear to us why the
counter needs to be reset at all. If we remove the lines that clear
the counter then there is no longer an issue with having both the mct
and the arch timers on at the same time.
Alternately, if there is some code that depends on the mct being reset
we could store an offset instead of clearing the counter and then
subtract that offset every time something reads it. Doug has a patch
that does this at
https://chromium-review.googlesource.com/#/c/200298/. Effectively the
visible behavior will not change. Would either of these options work?
Hi all,
Even though I've heard something about the behavior of mct and arch
timer...but I couldn't finish the talk to h/w guys yet. I need to talk
again in next week then I could provide some useful information. Sorry
for late and can you please wait a minute before deciding whatever.
Thanks,
Kukjin
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