On Tue, 25 Jan 2011, Russell King - ARM Linux wrote: > On Tue, Jan 25, 2011 at 03:12:24PM +0100, Thomas Gleixner wrote: > > On Tue, 25 Jan 2011, Russell King - ARM Linux wrote: > > > On Tue, Jan 25, 2011 at 02:23:10PM +0100, Thomas Gleixner wrote: > > > > In which way? I mean the generic code issues a call to the set_mode > > > > function when we leave the broadcast mode. So what should the generic > > > > code do more ? > > > > > > I can't say because these patches only add the hooks, there's no > > > implementation yet which uses the hooks. > > > > > > Given the description about _why_ those hooks are necessary, it seems > > > that something is required. Either we start adding custom hacks to > > > each clockevent driver as is done with this patch, or we get some > > > generic help in place. > > > > > > I'm not thrilled by the custom hack approach - and I thought the > > > clockevent stuff was created to stop this kind of thing happening. > > > > Yes, and it does the right thing: > > > > idle enter (where the cpu local tick device stops) > > > > tick_broadcast_oneshot_control(CLOCK_EVT_NOTIFY_BROADCAST_ENTER) > > > > clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN) > > tick_broadcast_set_event(dev->next_event, 1) > > > > idle exit > > > > tick_broadcast_oneshot_control(CLOCK_EVT_NOTIFY_BROADCAST_EXIT) > > > > clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT) > > tick_program_event(dev->next_event, 1) > > > > So the generic code has all the calls in place. If a clock chip > > implementation misses to set control registers in the > > CLOCK_EVT_MODE_ONESHOT case, then it's not a short coming of the > > generic code which needs magic hooks in the arch code. > > > > The same applies for the periodic mode switch, which is handled via > > tick_broadcast_on_off(). > > > > Am I missing something ? > > I quote Colin: > > | This doesn't work for oneshot timers if the TWD_TIMER_CONTROL register > | gets reset by cpu idle between twd_set_mode and twd_set_next_event. And I fear that he means the twd_set_mode(ONESHOT) call which happens during boot/cpuonline. The point is that the above function needs to be called from the cpu idle code to notify the clock events layer. The correct mechanism is clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER/EXIT). The existing callers are in: arch/x86/kernel/process.c drivers/acpi/acpi_pad.c drivers/acpi/processor_idle.c drivers/idle/intel_idle.c So i'm not surprised, that this wont work on ARM :) Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
