cheza: Monitor the WARM_RESET_L signal to hold AP

This change is a backup solution if JTAG_SRST gets fused out.

The WARM_RESET_L signal is wired to JTAG_SRST, such that we can
hold AP when servo/H1 programs the AP SPI flash. But when JTAG_SRST
gets fused out (just in case it happens), still have a way to hold
AP, i.e. overdriving the AP_RST_L and PS_HOLD signals.

The WARM_RESET_L signal is pulled by a rail from PMIC, the same as
POWER_GOOD. The drop of WARM_RESET_L may be caused by either servo/
cr50 holds the signal or its pull-up rail drops. We should handle
both cases.

Also add WARM_RESET_L as one of the power signals for debug purpose.

BRANCH=none
BUG=b:78194018, b:112723105, b:112564635
TEST=Ran "dut-control warm_reset:on" and "dut-control warm_reset:off".
Scoped the signal of AP_RST_L and PS_HOLD to verify the correctness.
Verified AP hold and back booting up.
TEST=Changed to the gpio.inc to swap LID_OPEN and WARM_RESET_L and
ran "dut-control lid_open:no" and "dut-control lid_open:yes" to emualte
the case JTAG_SRST gets fused out. Scoped the signal correctness.
Verified AP hold and back booting up. Ran flashrom to program AP SPI
flash through servo.

Change-Id: I71ebd920171da9994192f7742675feb7cb39ce2f
Signed-off-by: Wai-Hong Tam <waihong@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1234743

1 files changed, 64 insertions, 1 deletions

diff --git a/power/sdm845.c b/power/sdm845.c
index 6c5f033b44..36e041f96d 100644
--- a/power/sdm845.c
+++ b/power/sdm845.c
@@ -89,6 +89,9 @@ static char power_button_was_pressed;
 /* 1 if lid-open event has been detected */
 static char lid_opened;
 
+/* 1 if AP_RST_L and PS_HOLD is overdriven by EC */
+static char ap_rst_overdriven;
+
 /*
  * 1 if power state is controlled by special functions, like a console command
  * or an interrupt handler, for bypassing POWER_GOOD lost trigger. It is
@@ -153,6 +156,64 @@ void chipset_reset_request_interrupt(enum gpio_signal signal)
 	hook_call_deferred(&chipset_reset_request_handler_data, 0);
 }
 
+void chipset_warm_reset_interrupt(enum gpio_signal signal)
+{
+	/*
+	 * The warm_reset signal is pulled-up by a rail from PMIC. If the
+	 * warm_reset drops, it means:
+	 *  * Servo or Cr50 holds the signal, or
+	 *  * its pull-up rail POWER_GOOD drops.
+	 */
+	if (!gpio_get_level(GPIO_WARM_RESET_L)) {
+		if (gpio_get_level(GPIO_POWER_GOOD)) {
+			/*
+			 * Servo or Cr50 holds the WARM_RESET_L signal.
+			 *
+			 * Overdrive AP_RST_L to hold AP. Overdrive PS_HOLD to
+			 * emulate AP being up to trick the PMIC into thinking
+			 * there’s nothing weird going on.
+			 */
+			ap_rst_overdriven = 1;
+			gpio_set_flags(GPIO_PS_HOLD, GPIO_INT_BOTH |
+				       GPIO_SEL_1P8V | GPIO_OUT_HIGH);
+			gpio_set_flags(GPIO_AP_RST_L, GPIO_INT_BOTH |
+				       GPIO_SEL_1P8V | GPIO_OUT_LOW);
+		} else {
+			/*
+			 * The pull-up rail POWER_GOOD drops.
+			 *
+			 * High-Z both AP_RST_L and PS_HOLD to restore their
+			 * states.
+			 */
+			gpio_set_flags(GPIO_AP_RST_L, GPIO_INT_BOTH |
+				       GPIO_SEL_1P8V);
+			gpio_set_flags(GPIO_PS_HOLD, GPIO_INT_BOTH |
+				       GPIO_SEL_1P8V);
+			ap_rst_overdriven = 0;
+		}
+	} else {
+		if (ap_rst_overdriven) {
+			/*
+			 * Servo or Cr50 releases the WARM_RESET_L signal.
+			 *
+			 * High-Z both AP_RST_L and PS_HOLD to restore their
+			 * state. Cold reset the PMIC, doing S0->S5->S0
+			 * transition, to recover the system.
+			 */
+			gpio_set_flags(GPIO_AP_RST_L, GPIO_INT_BOTH |
+				       GPIO_SEL_1P8V);
+			gpio_set_flags(GPIO_PS_HOLD, GPIO_INT_BOTH |
+				       GPIO_SEL_1P8V);
+			ap_rst_overdriven = 0;
+
+			/* TODO(b/112723105): Do S0->S5->S0 transition here. */
+		}
+		/* If not overdriven, just a normal power-up, do nothing. */
+	}
+
+	power_signal_interrupt(signal);
+}
+
 static void sdm845_lid_event(void)
 {
 	/* Power task only cares about lid-open events */
@@ -328,8 +389,10 @@ enum power_state power_chipset_init(void)
 	int init_power_state;
 	uint32_t reset_flags = system_get_reset_flags();
 
-	/* Enable reboot control input from AP */
+	/* Enable interrupts */
 	gpio_enable_interrupt(GPIO_AP_RST_REQ);
+	gpio_enable_interrupt(GPIO_WARM_RESET_L);
+	gpio_enable_interrupt(GPIO_POWER_GOOD);
 
 	/*
 	 * Force the AP shutdown unless we are doing SYSJUMP. Otherwise,