Messages in this thread | | | Date | Thu, 25 Jun 2015 16:30:31 +0100 | From | Sudeep Holla <> | Subject | Re: [PATCH] clockevents: return error from tick_broadcast_oneshot_control if !GENERIC_CLOCKEVENTS_BROADCAST |
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On 25/06/15 14:55, Thomas Gleixner wrote: > On Thu, 25 Jun 2015, Sudeep Holla wrote: > >> tick_broadcast_enter returns 0 when CPU can switch to broadcast >> timer and non-zero otherwise. However when GENERIC_CLOCKEVENTS_BROADCAST >> and TICK_ONESHOT are disabled, tick_broadcast_oneshot_control returns 0 >> which indicates to the CPUIdle framework that the CPU can enter deeper >> idle states even when the CPU local timer will be shutdown. If the >> target state needs broadcast but not broadcast timer is available, then >> the CPU can not resume back from that idle state. >> >> This patch returns error when there's no broadcast timer support >> available so that CPUIdle framework prevents the CPU from entering any >> idle states losing the local timer. > > That's wrong and breaks stuff which does not require the broadcast > nonsense. >
OK, sorry for not considering that case.
> If TICK_ONESHOT is disabled, then everything is in periodic mode and > tick_broadcast_enter() rightfully returns 0. Ditto for 'highres=off' > on the command line. > > But there is a case which is not correctly handled right now. That's > what you are trying to solve in the wrong way. >
Correct I was trying to solve exactly the case mentioned below.
> If > GENERIC_CLOCKEVENTS_BROADCAST=n > > or > > GENERIC_CLOCKEVENTS_BROADCAST=y and no broadcast device is available, > > AND cpu local tick device has the C3STOP flag set, > > then we have no way to tell the idle code that going deep is not > allowed. > > So we need to be smarter than blindly changing a return > value. Completely untested patch below. >
Agreed, thanks for the quick patch, I have tested it and it works fine. You can add
Tested-by: Sudeep Holla <sudeep.holla@arm.com>
Regards, Sudeep
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