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

5 files changed, 85 insertions, 6 deletions

diff --git a/board/cheza/board.c b/board/cheza/board.c
index e1d85f91f2..4bf71eab01 100644
--- a/board/cheza/board.c
+++ b/board/cheza/board.c
@@ -204,6 +204,10 @@ const struct power_signal_info power_signal_list[] = {
 		GPIO_POWER_GOOD,
 		POWER_SIGNAL_ACTIVE_HIGH,
 		"POWER_GOOD"},
+	[SDM845_WARM_RESET] = {
+		GPIO_WARM_RESET_L,
+		POWER_SIGNAL_ACTIVE_HIGH,
+		"WARM_RESET_L"},
 };
 BUILD_ASSERT(ARRAY_SIZE(power_signal_list) == POWER_SIGNAL_COUNT);
 
diff --git a/board/cheza/board.h b/board/cheza/board.h
index ce83a439b6..9998233356 100644
--- a/board/cheza/board.h
+++ b/board/cheza/board.h
@@ -172,6 +172,7 @@ enum power_signal {
 	SDM845_PS_HOLD,
 	SDM845_PMIC_FAULT_L,
 	SDM845_POWER_GOOD,
+	SDM845_WARM_RESET,
 	/* Number of power signals */
 	POWER_SIGNAL_COUNT
 };
diff --git a/board/cheza/gpio.inc b/board/cheza/gpio.inc
index 49dbfdc008..3ba7840340 100644
--- a/board/cheza/gpio.inc
+++ b/board/cheza/gpio.inc
@@ -27,12 +27,17 @@ GPIO_INT(VOLUME_UP_L,       PIN(F, 2), GPIO_INT_BOTH | GPIO_PULL_UP, button_inte
 GPIO_INT(WP_L,              PIN(A, 1), GPIO_INT_BOTH, switch_interrupt)  /* EC_WP_ODL */
 GPIO_INT(LID_OPEN,          PIN(D, 2), GPIO_INT_BOTH | GPIO_HIB_WAKE_HIGH, lid_interrupt)  /* LID_OPEN_EC */
 GPIO_INT(AP_RST_REQ,        PIN(C, 2), GPIO_INT_RISING | GPIO_PULL_DOWN | GPIO_SEL_1P8V, chipset_reset_request_interrupt)  /* Reset request from AP */
-/* AP_RST_L and PS_HOLD are used for PMIC and AP negotiation. Don't change their states. */
 GPIO_INT(AP_RST_L,          PIN(C, 1), GPIO_INT_BOTH | GPIO_SEL_1P8V, power_signal_interrupt)
 GPIO_INT(PS_HOLD,           PIN(D, 4), GPIO_INT_BOTH | GPIO_PULL_DOWN | GPIO_SEL_1P8V, power_signal_interrupt)  /* Indicate when AP triggers reset/shutdown */
 GPIO_INT(PMIC_FAULT_L,      PIN(7, 6), GPIO_INT_BOTH | GPIO_SEL_1P8V, power_signal_interrupt)  /* Any PMIC fault? */
-/* When switch-cap is off, the POWER_GOOD signal is floating. Need a pull-down to make it low. */
-GPIO_INT(POWER_GOOD,        PIN(5, 4), GPIO_INT_BOTH | GPIO_PULL_DOWN | GPIO_SEL_1P8V, power_signal_interrupt)  /* SRC_PP1800_S4A from PMIC */
+/*
+ * When switch-cap is off, the POWER_GOOD signal is floating. Need a pull-down
+ * to make it low. Overload the interrupt function chipset_warm_reset_interrupt
+ * for not only signalling power_signal_interrupt but also handling the logic
+ * of WARM_RESET_L which is pulled-up by the same rail of POWER_GOOD.
+ */
+GPIO_INT(POWER_GOOD,        PIN(5, 4), GPIO_INT_BOTH | GPIO_PULL_DOWN | GPIO_SEL_1P8V, chipset_warm_reset_interrupt)  /* SRC_PP1800_S4A from PMIC */
+GPIO_INT(WARM_RESET_L,      PIN(F, 4), GPIO_INT_BOTH | GPIO_SEL_1P8V, chipset_warm_reset_interrupt)  /* AP warm reset */
 GPIO_INT(SHI_CS_L,          PIN(5, 3), GPIO_INT_FALLING | GPIO_PULL_DOWN | GPIO_SEL_1P8V, shi_cs_event)  /* AP_EC_SPI_CS_L */
 GPIO_INT(CC_LID_BASE_ADC,   PIN(4, 5), GPIO_INT_BOTH, base_detect_interrupt)  /* Base detection */
 
@@ -54,7 +59,6 @@ GPIO(PROCHOT_L,             PIN(3, 4), GPIO_INPUT)
 
 /* PMIC/AP 1.8V */
 GPIO(PM845_RESIN_L,         PIN(3, 2), GPIO_ODR_HIGH | GPIO_SEL_1P8V)  /* PMIC reset trigger */
-GPIO(WARM_RESET_L,          PIN(F, 4), GPIO_ODR_HIGH | GPIO_SEL_1P8V)  /* AP warm reset */
 GPIO(PMIC_KPD_PWR_ODL,      PIN(D, 6), GPIO_ODR_HIGH | GPIO_SEL_1P8V)  /* PMIC power button */
 GPIO(EC_INT_L,              PIN(A, 2), GPIO_ODR_HIGH | GPIO_SEL_1P8V)  /* Interrupt line between AP and EC */
 GPIO(AP_SUSPEND_L,          PIN(5, 7), GPIO_INPUT | GPIO_SEL_1P8V)     /* Suspend signal from AP */
diff --git a/include/chipset.h b/include/chipset.h
index b4b630f032..7363707b38 100644
--- a/include/chipset.h
+++ b/include/chipset.h
@@ -185,8 +185,8 @@ static inline void power_interrupt(enum gpio_signal signal) { }
 static inline void chipset_handle_espi_reset_assert(void) { }
 static inline void chipset_handle_reboot(void) { }
 static inline void chipset_reset_request_interrupt(enum gpio_signal signal) { }
+static inline void chipset_warm_reset_interrupt(enum gpio_signal signal) { }
 static inline void chipset_watchdog_interrupt(enum gpio_signal signal) { }
-static inline void chipset_power_signal_interrupt(enum gpio_signal signal) { }
 
 #endif /* !HAS_TASK_CHIPSET */
 
@@ -210,6 +210,13 @@ void chipset_handle_reboot(void);
 void chipset_reset_request_interrupt(enum gpio_signal signal);
 
 /**
+ * GPIO interrupt handler of warm reset signal from servo or H1.
+ *
+ * It is used in SDM845 chipset power sequence.
+ */
+void chipset_warm_reset_interrupt(enum gpio_signal signal);
+
+/**
  * GPIO interrupt handler of watchdog from AP.
  *
  * It is used in MT8183 chipset, where it must be setup to trigger on falling
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,