shinys000114/linux
1
0
Fork 0
mirror of https://github.com/hardkernel/linux.git synced 2026-06-09 20:32:04 +09:00
Code Issues Packages Projects Releases Wiki Activity

ARM: tegra: Handle timers during LP2 idle ticks

Browse Source 
Timer ticks aren't properly serviced while a CPU is in LP2 idle.
Although the Tegra LP2 idle code calls hrtimer_peek_ahead_timers,
because no IRQ regs have been saved, update_process_times is not
called, and thus the timer list is not serviced (and neither is
SMP rebalancing, etc.)  This can cause significant delays
scheduling timer-based activity, especially on CPU 1 (which is
not servicing most other IRQs).

Colin Cross suggested a patch based on upstream review feedback
that uses clock notifiers to switch to the "broadcast" clock event
source ("timer0" Tegra timer 3) during LP2, which has a real
interrupt handler defined that calls the clock event handler in
IRQ context, allowing timers to be checked.

Change-Id: Ifa3f4ec662f07dc9636e433f278358f75b65d10c
Signed-off-by: Todd Poynor <toddpoynor@google.com>
This commit is contained in:
Todd Poynor
2011-02-07 13:42:34 -08:00
parent da0fbc7f9b
commit 6b825e9aaa
1 changed files with 2 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
arch/arm/mach-tegra/cpuidle.c
View File

@@ -445,6 +445,7 @@ static int tegra_idle_enter_lp2(struct cpuidle_device *dev,
return tegra_idle_enter_lp3(dev, state);
local_irq_disable();
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &dev->cpu);
local_fiq_disable();
enter = ktime_get();
@@ -463,11 +464,9 @@ static int tegra_idle_enter_lp2(struct cpuidle_device *dev,
us = ktime_to_us(exit);
local_fiq_enable();
clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &dev->cpu);
local_irq_enable();
/* cpu clockevents may have been reset by powerdown */
hrtimer_peek_ahead_timers();
smp_rmb();
state->exit_latency = tegra_lp2_exit_latency;
state->target_residency = tegra_lp2_exit_latency +