On some ARM systems there are two sets of per-cpu timers: the TWD
timers and the global timers. The TWD timers are rated at 350 and
the global timers are rated at 300 but the TWD timers suffer from
FEAT_C3_STOP while the arm global timers don't. The tick device
selection logic doesn't consider the FEAT_C3_STOP flag so we'll
always end up with the TWD as the tick device although we don't
want that.
Extend the preference logic to take the FEAT_C3_STOP flag into
account and always prefer tick devices that don't suffer from
FEAT_C3_STOP even if their rating is lower than tick devices that
do suffer from FEAT_C3_STOP. This will remove the need to do any
broadcasting on such ARM systems.
Signed-off-by: Stephen Boyd <sb...@codeaurora.org>
---
kernel/time/tick-common.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 64522ec..3ae437d 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -244,12 +244,22 @@ static bool tick_check_preferred(struct
clock_event_device *curdev,
return false;
}
+ if (!curdev)
+ return true;
+
+ /* Always prefer a tick device that doesn't suffer from FEAT_C3STOP */
+ if (!(newdev->features & CLOCK_EVT_FEAT_C3STOP) &&
+ (curdev->features & CLOCK_EVT_FEAT_C3STOP))
+ return true;
+ if ((newdev->features & CLOCK_EVT_FEAT_C3STOP) &&
+ !(curdev->features & CLOCK_EVT_FEAT_C3STOP))
+ return false;
+
/*
* Use the higher rated one, but prefer a CPU local device with a lower
* rating than a non-CPU local device
*/
- return !curdev ||
- newdev->rating > curdev->rating ||
+ return newdev->rating > curdev->rating ||
!cpumask_equal(curdev->cpumask, newdev->cpumask);
}
--
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