Cr50: Set the default idle action to Sleep

When the Cr50 doesn't have anything else to do and it's been a
while since anyone has communicated with it (10 seconds via UART,
1 second via SPI, and the USB bus has stopped sending SOF
packets), it enters one of three idle states:

  wfi        = fully powered, just waiting for an interrupt.
  sleep      = low power mode, but RAM is preserved. It resumes quickly.
  deep sleep = hibernate. RAM is lost, resume is a warm boot

You can get/set the idle state with the "idle" console command.

BUG=chrome-os-partner:49955,chrome-os-partner:54331
BRANCH=none
TEST=make buildall

To test it:

* I've only tested on the debug board, because I need a serial
  console (not serial-over-USB) to see if it's asleep or not.

* I haven't been able to knowingly force USB Suspend on my
  workstation, so to fake it I just unplug the USB cables.

* Wait 10-12 seconds after typing anything on the serial console,
  then press a key. If the Cr50 was asleep, the first character
  will be lost. If it wasn't, you'll see the character echoed
  immediately.

Change-Id: Icc213e50b0c38f8c2b16bcd9960e2e5550b43180
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/356123
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>

1 files changed, 16 insertions, 5 deletions

diff --git a/chip/g/idle.c b/chip/g/idle.c
index dc003d3eef..1686474ba9 100644
--- a/chip/g/idle.c
+++ b/chip/g/idle.c
@@ -12,13 +12,17 @@
 
 /* What to do when we're just waiting */
 static enum {
-	IDLE_WFI,				/* default */
+	DONT_KNOW,
+	IDLE_WFI,
 	IDLE_SLEEP,
 	IDLE_DEEP_SLEEP,
 	NUM_CHOICES
 } idle_action;
 
+#define IDLE_DEFAULT IDLE_SLEEP
+
 static const char const *idle_name[] = {
+	"invalid",
 	"wfi",
 	"sleep",
 	"deep sleep",
@@ -31,7 +35,7 @@ static int command_idle(int argc, char **argv)
 
 	if (argc > 1) {
 		c = tolower(argv[1][0]);
-		for (i = 0; i < ARRAY_SIZE(idle_name); i++)
+		for (i = 1; i < ARRAY_SIZE(idle_name); i++)
 			if (idle_name[i][0] == c) {
 				idle_action = i;
 				break;
@@ -129,10 +133,17 @@ void __idle(void)
 {
 	int sleep_ok, sleep_delay_passed;
 
-	/* Preserved across soft reboots, but not hard */
+	/*
+	 * This register is preserved across soft reboots, but not hard. It
+	 * defaults to zero, which is how we can tell whether this is the
+	 * preserved value or not. We only need to remember it because we might
+	 * change it with the console command.
+	 */
 	idle_action = GREG32(PMU, PWRDN_SCRATCH17);
-	if (idle_action >= NUM_CHOICES)
-		idle_action = IDLE_WFI;
+	if (idle_action == DONT_KNOW || idle_action >= NUM_CHOICES) {
+		idle_action = IDLE_DEFAULT;
+		GREG32(PMU, PWRDN_SCRATCH17) = idle_action;
+	}
 
 	while (1) {