Improve cpu_idle when PM is disabled

Split cpu_idle() into cpu_idle_delay() and cpu_idle_job() rather than
requesting the idle type as a function argument. Have those functions
provide a default polling (non-PM) implentation which spin at the
lowest SMT priority.

This moves all the decrementer delay code into the CPU idle code rather
than the caller.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

1 files changed, 8 insertions, 20 deletions

diff --git a/core/timebase.c b/core/timebase.c
index a3c0fec..ca961c3 100644
--- a/core/timebase.c
+++ b/core/timebase.c
@@ -24,8 +24,8 @@ unsigned long tb_hz = 512000000;
 
 static void time_wait_poll(unsigned long duration)
 {
-	unsigned long remaining = duration;
-	unsigned long end = mftb() + duration;
+	unsigned long now = mftb();
+	unsigned long end = now + duration;
 	unsigned long period = msecs_to_tb(5);
 
 	if (this_cpu()->tb_invalid) {
@@ -33,7 +33,9 @@ static void time_wait_poll(unsigned long duration)
 		return;
 	}
 
-	while (tb_compare(mftb(), end) != TB_AAFTERB) {
+	while (tb_compare(now, end) != TB_AAFTERB) {
+		unsigned long remaining = end - now;
+
 		/* Call pollers periodically but not continually to avoid
 		 * bouncing cachelines due to lock contention. */
 		if (remaining >= period) {
@@ -43,7 +45,7 @@ static void time_wait_poll(unsigned long duration)
 		} else
 			time_wait_nopoll(remaining);
 
-		cpu_relax();
+		now = mftb();
 	}
 }
 
@@ -64,28 +66,14 @@ void time_wait(unsigned long duration)
 
 void time_wait_nopoll(unsigned long duration)
 {
-	unsigned long end = mftb() + duration;
-	unsigned long min = usecs_to_tb(10);
+	unsigned long min_sleep = usecs_to_tb(10);
 
 	if (this_cpu()->tb_invalid) {
 		cpu_relax();
 		return;
 	}
 
-	for (;;) {
-		uint64_t delay, tb = mftb();
-
-		if (tb_compare(tb, end) == TB_AAFTERB)
-			break;
-		delay = end - tb;
-		if (delay >= 0x7fffffff)
-			delay = 0x7fffffff;
-		if (delay >= min) {
-			mtspr(SPR_DEC, delay);
-			cpu_idle(cpu_wake_on_dec);
-		} else
-			cpu_relax();
-	}
+	cpu_idle_delay(duration, min_sleep);
 }
 
 void time_wait_ms(unsigned long ms)