power: common: Prevent console spam.

The power state driver would print out the current power state along
with its signals everytime a power signal interrupt was fired.  On some
systems, a signal may briefly go low and then come back before our
chipset module has a chance to notice.  This causes what appears to be
duplicate prints.

This commit tries to only print out the current power state when
something has actually changed.  If the input power signals or state
differs from the last time it checked, then the information will be
printed.

BUG=None
BRANCH=gru
TEST=Find a kevin where PGOOD goes away quite frequently.  Build and
flash; Verify that significantly less "power state S0" console spam is
emitted.
TEST=Verify that all state transitions are still printed.

Change-Id: I9d66c04e2ed79ab203c54f0a8dad82f32856bbf0
Signed-off-by: Aseda Aboagye <aaboagye@google.com>
Reviewed-on: https://chromium-review.googlesource.com/388761
Commit-Ready: Aseda Aboagye <aaboagye@chromium.org>
Tested-by: Aseda Aboagye <aaboagye@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>

1 files changed, 16 insertions, 2 deletions

diff --git a/power/common.c b/power/common.c
index 7e213f0569..83fd2a302d 100644
--- a/power/common.c
+++ b/power/common.c
@@ -373,10 +373,24 @@ void chipset_exit_hard_off(void)
 void chipset_task(void)
 {
 	enum power_state new_state;
+	static enum power_state last_state;
+	uint32_t this_in_signals;
+	static uint32_t last_in_signals;
 
 	while (1) {
-		CPRINTS("power state %d = %s, in 0x%04x",
-			state, state_names[state], in_signals);
+		/*
+		 * In order to prevent repeated console spam, only print the
+		 * current power state if something has actually changed.  It's
+		 * possible that one of the power signals goes away briefly and
+		 * comes back by the time we update our in_signals.
+		 */
+		this_in_signals = in_signals;
+		if (this_in_signals != last_in_signals || state != last_state) {
+			CPRINTS("power state %d = %s, in 0x%04x",
+				state, state_names[state], this_in_signals);
+			last_in_signals = this_in_signals;
+			last_state = state;
+		}
 
 		/* Always let the specific chipset handle the state first */
 		new_state = power_handle_state(state);