pd: Add support for multiple distinct TCPC alert signals

If multiple TCPCs are present on a system then we may have multiple
alert signals, each of which alerts us to the status of a different
TCPC. Make boards with external non cros-ec TCPCs define
tcpc_get_alert_status, which returns alert status based upon any alert
GPIOs present, and then service only ports which are alerting.

BUG=chromium:551683,chrome-os-partner:47851
TEST=Verify snoball PDCMD task sleeps appropriately when no devices are
inserted, and verify ports go to PD_DISCOVERY state when we attach
samus. Also verify that glados / glados_pd can still negotiate PD.
BRANCH=None

Change-Id: Iae6c4e1ef4d6685cb5bf7feef713505925a07c8c
Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/313209
Commit-Ready: Shawn N <shawnn@chromium.org>
Tested-by: Shawn N <shawnn@chromium.org>
Reviewed-by: Alec Berg <alecaberg@chromium.org>

board/pdeval-stm32f072/board.c

@@ -61,3 +61,17 @@ const struct tcpc_config_t tcpc_config[CONFIG_USB_PD_PORT_COUNT] = {
 	{I2C_PORT_TCPC, TCPC2_I2C_ADDR},
 #endif
 };
+
+uint16_t tcpc_get_alert_status(void)
+{
+	uint16_t status = 0;
+
+	if (!gpio_get_level(GPIO_PD_MCU_INT)) {
+		status = PD_STATUS_TCPC_ALERT_0;
+#if CONFIG_USB_PD_PORT_COUNT >= 2
+		status |= PD_STATUS_TCPC_ALERT_1;
+#endif
+	}
+
+	return status;
+}

board/snoball/board.c

@@ -41,6 +41,20 @@ const struct tcpc_config_t tcpc_config[CONFIG_USB_PD_PORT_COUNT] = {
 	{STM32_I2C2_PORT, FUSB302_I2C_SLAVE_ADDR + 2},
 };
 
+uint16_t tcpc_get_alert_status(void)
+{
+	uint16_t status = 0;
+
+	if (!gpio_get_level(GPIO_TCPC1_INT))
+		status |= PD_STATUS_TCPC_ALERT_0;
+	if (!gpio_get_level(GPIO_TCPC2_INT))
+		status |= PD_STATUS_TCPC_ALERT_1;
+	if (!gpio_get_level(GPIO_TCPC3_INT))
+		status |= PD_STATUS_TCPC_ALERT_2;
+
+	return status;
+}
+
 /* ADC channels */
 const struct adc_t adc_channels[] = {
 	/* Current sensing. Converted to mA (6600mV/4096). */

board/snoball/gpio.inc

@@ -39,8 +39,6 @@ GPIO(OPTO_OUT,		PIN(A, 8),	GPIO_OUT_LOW)
 /* Unimplemented signals which we need to emulate for now */
 UNIMPLEMENTED(ENTERING_RW)
 UNIMPLEMENTED(WP_L)
-/* TODO(crbug.com/551683): Add support for multiple alert GPIOs */
-UNIMPLEMENTED(PD_MCU_INT)
 
 /* Alternate functions */
 #if 0

common/host_command_pd.c

@@ -133,16 +133,25 @@ static void pd_check_chg_status(struct ec_response_pd_status *pd_status)
 #endif /* CONFIG_HOSTCMD_PD */
 
 #ifdef USB_TCPM_WITH_OFF_CHIP_TCPC
-static void pd_check_tcpc_alert(struct ec_response_pd_status *pd_status)
+static void pd_service_tcpc_ports(uint16_t port_status)
 {
 	int i;
 
 	for (i = 0; i < CONFIG_USB_PD_PORT_COUNT; i++) {
-		if (!pd_status ||
-		    (pd_status->status & (PD_STATUS_TCPC_ALERT_0 << i)))
+		if (port_status & (PD_STATUS_TCPC_ALERT_0 << i))
 			tcpc_alert(i);
 	}
 }
+
+static int pd_get_alert(void)
+{
+#ifdef CONFIG_HOSTCMD_PD
+	return !gpio_get_level(GPIO_PD_MCU_INT);
+#else
+	return !!tcpc_get_alert_status();
+#endif
+}
+
 #endif /* USB_TCPM_WITH_OFF_CHIP_TCPC */
 
 static void pd_exchange_status(uint32_t ec_state)
@@ -179,16 +188,15 @@ static void pd_exchange_status(uint32_t ec_state)
 
 #ifdef USB_TCPM_WITH_OFF_CHIP_TCPC
 #ifdef CONFIG_HOSTCMD_PD
-		pd_check_tcpc_alert(&pd_status);
+		pd_service_tcpc_ports(pd_status.status);
 #else
-		pd_check_tcpc_alert(NULL);
+		pd_service_tcpc_ports(tcpc_get_alert_status());
 #endif
 
-		if (!first_exchange) {
+		if (!first_exchange)
 			usleep(50*MSEC);
-			first_exchange = 0;
-		}
-	} while (!gpio_get_level(GPIO_PD_MCU_INT));
+		first_exchange = 0;
+	} while (pd_get_alert());
 #endif /* USB_TCPM_WITH_OFF_CHIP_TCPC */
 }
 

include/usb_pd_tcpm.h

@@ -56,6 +56,14 @@ struct tcpc_config_t {
 	 */
 };
 
+/**
+ * Returns the PD_STATUS_TCPC_ALERT_* mask corresponding to the TCPC ports
+ * that are currently asserting ALERT.
+ *
+ * @return     PD_STATUS_TCPC_ALERT_* mask.
+ */
+uint16_t tcpc_get_alert_status(void);
+
 /**
  * Initialize TCPM driver and wait for TCPC readiness.
  *