| Message ID | 1379530118-22813-4-git-send-email-soren.brinkmann@xilinx.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 09/18/2013 08:48 PM, Soren Brinkmann wrote: > On most ARM systems the per-cpu clockevents are truly per-cpu in > the sense that they can't be controlled on any other CPU besides > the CPU that they interrupt. If one of these clockevents were to > become a broadcast source we will run into a lot of trouble > because the broadcast source is enabled on the first CPU to go > into deep idle (if that CPU suffers from FEAT_C3_STOP) and that > could be a different CPU than what the clockevent is interrupting > (or even worse the CPU that the clockevent interrupts could be > offline). > > Theoretically it's possible to support per-cpu clockevents as the > broadcast source but so far we haven't needed this and supporting > it is rather complicated. Let's just deny the possibility for now > until this becomes a reality (let's hope it never does!). > > Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com> Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org> > --- > kernel/time/tick-broadcast.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c > index 218bcb5..9532690 100644 > --- a/kernel/time/tick-broadcast.c > +++ b/kernel/time/tick-broadcast.c > @@ -70,6 +70,7 @@ static bool tick_check_broadcast_device(struct clock_event_device *curdev, > struct clock_event_device *newdev) > { > if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) || > + (newdev->features & CLOCK_EVT_FEAT_PERCPU) || > (newdev->features & CLOCK_EVT_FEAT_C3STOP)) > return false; > >
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c index 218bcb5..9532690 100644 --- a/kernel/time/tick-broadcast.c +++ b/kernel/time/tick-broadcast.c @@ -70,6 +70,7 @@ static bool tick_check_broadcast_device(struct clock_event_device *curdev, struct clock_event_device *newdev) { if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) || + (newdev->features & CLOCK_EVT_FEAT_PERCPU) || (newdev->features & CLOCK_EVT_FEAT_C3STOP)) return false;
On most ARM systems the per-cpu clockevents are truly per-cpu in the sense that they can't be controlled on any other CPU besides the CPU that they interrupt. If one of these clockevents were to become a broadcast source we will run into a lot of trouble because the broadcast source is enabled on the first CPU to go into deep idle (if that CPU suffers from FEAT_C3_STOP) and that could be a different CPU than what the clockevent is interrupting (or even worse the CPU that the clockevent interrupts could be offline). Theoretically it's possible to support per-cpu clockevents as the broadcast source but so far we haven't needed this and supporting it is rather complicated. Let's just deny the possibility for now until this becomes a reality (let's hope it never does!). Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com> --- kernel/time/tick-broadcast.c | 1 + 1 file changed, 1 insertion(+)