[PATCH 1/1] arm: kernel: idle loop pm constraints

[Samu Onkalo]

Check pm qos cpu latency requirements before preparing for pm-idle activities.
Scheduling is prevented during those operations and interrupt thread serving
latency in increased. Driver can set pm qos latency requirement to zero to
indicate extreme tight latency needs.

Signed-off-by: Samu Onkalo <samu.p.onkalo at nokia.com>
---
 arch/arm/kernel/process.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 401e38b..3645947 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -29,6 +29,7 @@
 #include <linux/utsname.h>
 #include <linux/uaccess.h>
 #include <linux/random.h>
+#include <linux/pm_qos_params.h>
 
 #include <asm/cacheflush.h>
 #include <asm/leds.h>
@@ -162,6 +163,12 @@ void cpu_idle(void)
 
 	/* endless idle loop with no priority at all */
 	while (1) {
+		if (pm_qos_requirement(PM_QOS_CPU_DMA_LATENCY) == 0) {
+			preempt_enable_no_resched();
+			schedule();
+			preempt_disable();
+			continue;
+		}
 		tick_nohz_stop_sched_tick(1);
 		leds_event(led_idle_start);
 		while (!need_resched()) {
-- 
1.6.3.3