nyan: bring back set_ap_reset() for old boards.

Since some folks are still using old boards (rev <= 2.0), bring this back
so that they can reset system gracefully.

BUG=None
BRANCH=nyan
TEST=tested on rev 2.0
reboot  // EC and AP are rebooted
reset button on board  // EC and AP are reset
power off  // AP (rev 2.0) is expected NOT powered off.
power on

Change-Id: I35dbc5648b092c892dc06ce5676e1e68c695d477
Signed-off-by: Louis Yung-Chieh Lo <yjlou@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/179851
Reviewed-by: Randall Spangler <rspangler@chromium.org>

1 files changed, 22 insertions, 1 deletions

diff --git a/power/tegra.c b/power/tegra.c
index e865011bc3..83dc47bd58 100644
--- a/power/tegra.c
+++ b/power/tegra.c
@@ -143,6 +143,23 @@ static int wait_in_signal(enum gpio_signal signal, int value, int timeout)
 }
 
 /**
+ * Set the AP RESET signal.
+ *
+ * This fucntion is for backward-compatible.
+ *
+ * AP_RESET_L (PB3) is stuffed before rev <= 2.0 and connected to PMIC RESET.
+ * After rev >= 2.2, this is removed. This should not effected the new board.
+ *
+ * @param asserted  Assert (=1) or deassert (=0) the signal.  This is the
+ *                  logical level of the pin, not the physical level.
+ */
+static void set_ap_reset(int asserted)
+{
+	/* Signal is active-low */
+	gpio_set_level(GPIO_AP_RESET_L, asserted ? 0 : 1);
+}
+
+/**
  * Set the PMIC PWRON signal.
  *
  * Note that asserting requires holding for PMIC_PWRON_DEBOUNCE_TIME.
@@ -368,6 +385,9 @@ void chipset_force_shutdown(void)
 	set_pmic_therm(1);
 	udelay(PMIC_THERM_HOLD_TIME);
 	set_pmic_therm(0);
+
+	/* Hold the reset pin so that the AP stays in off mode (rev <= 2.0) */
+	set_ap_reset(1);
 }
 
 /*****************************************************************************/
@@ -421,8 +441,9 @@ static int check_for_power_on_event(void)
  */
 static int power_on(void)
 {
-	/* Make sure we de-assert the PMI_THERM_L pin. */
+	/* Make sure we de-assert the PMI_THERM_L and AP_RESET_L pin. */
 	set_pmic_therm(0);
+	set_ap_reset(0);
 
 	/* Push the power button */
 	set_pmic_pwron(1);