sc7180: Monitor AP_RST_L from PMIC to notify HOOK_CHIPSET_RESET

The HOOK_CHIPSET_RESET should be notified when the AP resets.

In x86 platforms, EC monitors the LPC LRESET pin. This LRESET pin is
asserted when the chipset resets. However, ARM platforms don't use
LPC. We need another way to monitor AP reset.

This CL modifies the SC7180 power sequence, to monitor the AP_RST_L
signal from PMIC. PMIC uses the AP_RST_L to notify AP reset. A
complete warm reset sequence will toggle the AP_RST_L signal 3 times.
EC monitors the AP_RST_L signal and wait it transition 3 times to
notify the HOOK_CHIPSET_RESET. In case, the AP_RST_L is not toggled
3 times, still notifies the hook but prints a warning message.

BRANCH=None
BUG=b:163078082
TEST=Checked the HOOK_CHIPSET_RESET is notified after AP warm reset.

Change-Id: I4e7b0f0d266e01526deaf54afcdfd2ac1037b8f6
Signed-off-by: Wai-Hong Tam <waihong@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2343753
Reviewed-by: Stephen Boyd <swboyd@chromium.org>

1 files changed, 57 insertions, 0 deletions

diff --git a/power/sc7180.c b/power/sc7180.c
index fe093ad535..69c64206d4 100644
--- a/power/sc7180.c
+++ b/power/sc7180.c
@@ -100,6 +100,16 @@
  */
 #define PMIC_POWER_OFF_DELAY		(70 * MSEC)
 
+/* The AP_RST_L transition count of a normal AP warm reset */
+#define EXPECTED_AP_RST_TRANSITIONS	3
+
+/*
+ * The timeout of waiting the next AP_RST_L transition. We measured
+ * the interval between AP_RST_L transitions is 130ms ~ 150ms. Pick
+ * a safer value.
+ */
+#define AP_RST_TRANSITION_TIMEOUT	(450 * MSEC)
+
 /* TODO(crosbug.com/p/25047): move to HOOK_POWER_BUTTON_CHANGE */
 /* 1 if the power button was pressed last time we checked */
 static char power_button_was_pressed;
@@ -155,6 +165,53 @@ enum power_on_event_t {
 	POWER_ON_EVENT_COUNT,
 };
 
+#ifdef CONFIG_CHIPSET_RESET_HOOK
+static int ap_rst_transitions;
+
+static void notify_chipset_reset(void)
+{
+	if (ap_rst_transitions != EXPECTED_AP_RST_TRANSITIONS)
+		CPRINTS("AP_RST_L transitions not expected: %d",
+			ap_rst_transitions);
+
+	ap_rst_transitions = 0;
+	hook_notify(HOOK_CHIPSET_RESET);
+}
+DECLARE_DEFERRED(notify_chipset_reset);
+#endif
+
+void chipset_ap_rst_interrupt(enum gpio_signal signal)
+{
+#ifdef CONFIG_CHIPSET_RESET_HOOK
+	int delay;
+
+	/*
+	 * Only care the raising edge and AP in S0/S3. The single raising edge
+	 * of AP power-on during S5S3 is ignored.
+	 */
+	if (gpio_get_level(GPIO_AP_RST_L) &&
+	    chipset_in_state(CHIPSET_STATE_ON | CHIPSET_STATE_SUSPEND)) {
+		ap_rst_transitions++;
+		if (ap_rst_transitions >= EXPECTED_AP_RST_TRANSITIONS) {
+			/*
+			 * Reach the expected transition count. AP is booting
+			 * up. Notify HOOK_CHIPSET_RESET immediately.
+			 */
+			delay = 0;
+		} else {
+			/*
+			 * Should have more transitions of the AP_RST_L signal.
+			 * In case the AP_RST_L signal is not toggled, still
+			 * notify HOOK_CHIPSET_RESET.
+			 */
+			delay = AP_RST_TRANSITION_TIMEOUT;
+		}
+		hook_call_deferred(&notify_chipset_reset_data, delay);
+	}
+#endif
+	power_signal_interrupt(signal);
+}
+
 /* Issue a request to initiate a reset sequence */
 static void request_cold_reset(void)
 {