coffeecake: Workaround P0 EN_USB_PD leakage

EN_USB_PD leaks ~1V to C0_VBUS. This change turns on PD_DISCHARGE when
C0_VBUS is low.

BRANCH=none
BUG=b:67910512
TEST=manual
  load on coffeecake, boot into SRC mode, check C0_VBUS voltage.

Change-Id: Ia650ee83c8fef4228d3bb2f7ec5f9eab3e16bf4d
Signed-off-by: Rong Chang <rongchang@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/758318
Reviewed-by: Benson Leung <bleung@chromium.org>

3 files changed, 39 insertions, 17 deletions

diff --git a/board/coffeecake/board.c b/board/coffeecake/board.c
index bc44f07a00..11b4180c0e 100644
--- a/board/coffeecake/board.c
+++ b/board/coffeecake/board.c
@@ -27,6 +27,7 @@ static volatile uint64_t hpd_prev_ts;
 static volatile int hpd_prev_level;
 
 void hpd_event(enum gpio_signal signal);
+void vbus_event(enum gpio_signal signal);
 #include "gpio_list.h"
 
 /* I2C ports */
@@ -102,6 +103,13 @@ void hpd_event(enum gpio_signal signal)
 	hpd_prev_level = level;
 }
 
+/* Proto 0 workaround */
+void vbus_event(enum gpio_signal signal)
+{
+	/* Discharge VBUS on DET_L high */
+	gpio_set_level(GPIO_PD_DISCHARGE, gpio_get_level(signal));
+}
+
 /* USB C VBUS output selection */
 void board_set_usb_output_voltage(int mv)
 {
@@ -111,15 +119,21 @@ void board_set_usb_output_voltage(int mv)
 	int dac_mv;
 	uint32_t dac_val;
 
-	/* vbat = 1.0 * ra/rb + 1.0 - (vdac - 1.0) * ra/rc */
-	dac_mv = 1000 + (1000 * rc / rb) + ((1000 - mv) * rc / ra);
-	if (dac_mv < 0)
-		dac_mv = 0;
-
-	/* Set voltage Vout=Vdac with Vref = 3.3v */
-	/* TODO: use Vdda instead */
-	dac_val = dac_mv * 4096 / 3300;
-	STM32_DAC_DHR12RD = dac_val | (dac_val << 16);
+	if (mv >= 0) {
+		/* vbat = 1.0 * ra/rb + 1.0 - (vdac - 1.0) * ra/rc */
+		dac_mv = 1000 + (1000 * rc / rb) + ((1000 - mv) * rc / ra);
+		if (dac_mv < 0)
+			dac_mv = 0;
+
+		/* Set voltage Vout=Vdac with Vref = 3.3v */
+		/* TODO: use Vdda instead */
+		dac_val = dac_mv * 4096 / 3300;
+		/* Start DAC channel 2 */
+		STM32_DAC_DHR12RD = dac_val << 16;
+		STM32_DAC_CR = STM32_DAC_CR_EN2;
+	} else {
+		STM32_DAC_CR = 0;
+	}
 }
 
 /* Initialize board. */
@@ -131,8 +145,6 @@ void board_config_pre_init(void)
 	STM32_RCC_APB1ENR |= (1 << 29);
 	/* Delay 1 APB clock cycle after the clock is enabled */
 	clock_wait_bus_cycles(BUS_APB, 1);
-	/* Start DAC channel 1 & 2 */
-	STM32_DAC_CR = STM32_DAC_CR_EN1 | STM32_DAC_CR_EN2;
 	/* Set 5Vsafe Vdac */
 	board_set_usb_output_voltage(5000);
 	/* Remap USART DMA to match the USART driver */
@@ -213,6 +225,10 @@ static void board_init(void)
 	hpd_prev_level = gpio_get_level(GPIO_DP_HPD);
 	hpd_prev_ts = now.val;
 	gpio_enable_interrupt(GPIO_DP_HPD);
+	gpio_enable_interrupt(GPIO_CHARGER_INT);
+	gpio_enable_interrupt(GPIO_USB_C_VBUS_DET_L);
+	/* Set PD_DISCHARGE initial state */
+	gpio_set_level(GPIO_PD_DISCHARGE, gpio_get_level(GPIO_USB_C_VBUS_DET_L));
 
 	/* Delay needed to allow HDMI MCU to boot. */
 	hook_call_deferred(&factory_validation_deferred_data, 200*MSEC);
diff --git a/board/coffeecake/gpio.inc b/board/coffeecake/gpio.inc
index bc0fea43e2..0c1665a5d9 100644
--- a/board/coffeecake/gpio.inc
+++ b/board/coffeecake/gpio.inc
@@ -8,8 +8,9 @@
 /* Declare symbolic names for all the GPIOs that we care about.
  * Note: Those with interrupt handlers must be declared first. */
 
-GPIO_INT(DP_HPD,       PIN(A, 0),  GPIO_INT_BOTH, hpd_event)
-GPIO_INT(CHARGER_INT,  PIN(C, 13), GPIO_INT_FALLING, sy21612_int)
+GPIO_INT(DP_HPD,           PIN(A, 0),  GPIO_INT_BOTH, hpd_event)
+GPIO_INT(CHARGER_INT,      PIN(C, 13), GPIO_INT_FALLING, sy21612_int)
+GPIO_INT(USB_C_VBUS_DET_L, PIN(C, 14), GPIO_INT_BOTH, vbus_event)
 
 GPIO(USB_C_CC1_PD,     PIN(A, 1),  GPIO_ANALOG)
 GPIO(VBUS_DIV4_MON,    PIN(A, 2),  GPIO_ANALOG)
@@ -35,7 +36,6 @@ GPIO(I2C0_SDA,         PIN(B, 7),  GPIO_INPUT)
 GPIO(LED_ORANGE,       PIN(B, 9),  GPIO_OUT_LOW)
 GPIO(PD_MCDP_SPI_CS_L, PIN(B, 12), GPIO_INPUT)
 
-GPIO(USB_C_VBUS_DET_L, PIN(C, 14), GPIO_INPUT)
 GPIO(AC_PRESENT_L,     PIN(C, 15), GPIO_INPUT)
 
 GPIO(EN_PP5000,        PIN(F,  0), GPIO_OUT_HIGH)
diff --git a/board/coffeecake/usb_pd_policy.c b/board/coffeecake/usb_pd_policy.c
index b0fb437bd6..660e45e90e 100644
--- a/board/coffeecake/usb_pd_policy.c
+++ b/board/coffeecake/usb_pd_policy.c
@@ -83,19 +83,25 @@ void pd_transition_voltage(int idx)
 
 int pd_set_power_supply_ready(int port)
 {
+	/* Turn on DAC and adjust feedback to get 5V output */
+	board_set_usb_output_voltage(5000);
+	/* Enable Vsys to USBC Vbus charging */
 	sy21612_set_sink_mode(1);
-	sy21612_set_vbus_volt(SY21612_VBUS_9V);
 	sy21612_set_adc_mode(1);
 	sy21612_enable_adc(1);
-	sy21612_set_vbus_discharge(1);
+	sy21612_set_vbus_discharge(0);
 	return EC_SUCCESS;
 }
 
 void pd_power_supply_reset(int port)
 {
-	board_set_usb_output_voltage(5000);
+	/* Turn off DAC output */
+	board_set_usb_output_voltage(-1);
+	/* Turn off USBC VBUS output */
 	sy21612_set_sink_mode(0);
+	/* Set boost Vsys output 9V */
 	sy21612_set_vbus_volt(SY21612_VBUS_9V);
+	/* Turn on buck-boost converter ADC */
 	sy21612_set_adc_mode(1);
 	sy21612_enable_adc(1);
 	sy21612_set_vbus_discharge(1);