Skylake: Add low power Pseudo G3 support

BUG=none
TEST=Used "shutdown -h now" Kernel console command to test on Kunimitsu.
     With only battery after 1 hour, device enters to Pseudo G3 and the
     V3p3A is off. With AC connected, device is in G3.
BRANCH=none

Change-Id: I955662eb69ac608e9b2d12bdcfbc1258ca83f3a5
Signed-off-by: Vijay Hiremath <vijay.p.hiremath@intel.com>
Reviewed-on: https://chromium-review.googlesource.com/292976
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

board/kunimitsu/board.h

@@ -113,8 +113,8 @@
 #undef CONFIG_CONSOLE_HISTORY
 #undef CONFIG_PECI
 
-/* Enable sleep mode in G3 */
-#define CONFIG_G3_SLEEP
+/* Enable Pseudo G3 */
+#define CONFIG_LOW_POWER_PSEUDO_G3
 
 #ifndef __ASSEMBLER__
 

include/config.h

@@ -1146,9 +1146,6 @@
  */
 #undef CONFIG_LOW_POWER_S0
 
-/* Support G3 sleep mode */
-#undef CONFIG_G3_SLEEP
-
 /* Support LPC interface */
 #undef CONFIG_LPC
 

power/skylake.c

@@ -279,9 +279,6 @@ static enum power_state _power_handle_state(enum power_state state)
 		return POWER_S5;
 
 	case POWER_S5G3:
-#ifdef CONFIG_G3_SLEEP
-		gpio_set_level(GPIO_G3_SLEEP_EN, 1);
-#endif
 		chipset_force_g3();
 		return POWER_G3;
 
@@ -340,3 +337,22 @@ enum power_state power_handle_state(enum power_state state)
 
 	return new_state;
 }
+
+#ifdef CONFIG_LOW_POWER_PSEUDO_G3
+void enter_pseudo_g3(void)
+{
+	CPRINTS("Enter Psuedo G3");
+
+	/*
+	 * Clean up the UART buffer and prevent any unwanted garbage characters
+	 * before power off and also ensure above debug message is printed.
+	 */
+	cflush();
+
+	gpio_set_level(GPIO_G3_SLEEP_EN, 1);
+
+	/* Power to EC should shut down now */
+	while (1)
+		;
+}
+#endif