Messages in this thread | | | Date | Tue, 18 Jun 2013 16:32:07 +0900 | Subject | Re: [PATCH/RFC] arm: arch_timer: Do not set C3STOP in case CPU_IDLE=n | From | Magnus Damm <> |
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Hi Mark,
On Mon, Jun 17, 2013 at 11:53 PM, Mark Rutland <mark.rutland@arm.com> wrote: > On Mon, Jun 17, 2013 at 01:20:56AM +0100, Magnus Damm wrote: >> From: Magnus Damm <damm@opensource.se> >> >> Modify the ARM architected timer driver to not set C3STOP >> in case CPU_IDLE is disabled. This is a short term fix that >> allows use of high resolution timers even though no additional >> clock event is registered. >> >> Not-really-Signed-off-by: Magnus Damm <damm@opensource.se> >> --- >> >> If someone cares about this case then perhaps it should be >> moved up to the clock event main code. The same issue should >> in theory trigger on all architectures, perhaps x86 people >> hunting for low latency may try to disable CPU_IDLE? > > I think that changing tick_is_oneshot_capable and friends to only worry about > C3STOP when CPU_IDLE is enabled would be a nicer solution. That way you enable > all clock_event_devices with C3STOP to function as high resolution timers when > CPU_IDLE's selected. Presenting the hardware differently depending on CPU_IDLE > feels wrong.
I agree that doing this in the clock event driver is a bit odd. So because of that I just posted this patch:
[PATCH/RFC] clockevents: Ignore C3STOP when CPUIdle is disabled
> Having some other clock_event_device would be a nicer solution still.
No doubt that another clock event device helps, but mainly together with CPU Idle IMO.
Thanks for your comments!
/ magnus
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