platform/chrome: cros_typec_switch: Add Pin D support

The ChromeOS EC's mux interface allows us to specify whether the port
should be configured for Pin Assignment D in DisplayPort alternate mode
(i.e 2 lanes USB + 2 lanes DP). Update the function that determines mux
state to account for Pin Assignment D and return the appropriate mux
setting.

Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Prashant Malani <pmalani@chromium.org>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20230508183428.1893357-1-pmalani@chromium.org

drivers/platform/chrome/cros_typec_switch.c

@@ -51,13 +51,18 @@ static int cros_typec_cmd_mux_set(struct cros_typec_switch_data *sdata, int port
 static int cros_typec_get_mux_state(unsigned long mode, struct typec_altmode *alt)
 {
 	int ret = -EOPNOTSUPP;
+	u8 pin_assign;
 
-	if (mode == TYPEC_STATE_SAFE)
+	if (mode == TYPEC_STATE_SAFE) {
 		ret = USB_PD_MUX_SAFE_MODE;
-	else if (mode == TYPEC_STATE_USB)
+	} else if (mode == TYPEC_STATE_USB) {
 		ret = USB_PD_MUX_USB_ENABLED;
-	else if (alt && alt->svid == USB_TYPEC_DP_SID)
+	} else if (alt && alt->svid == USB_TYPEC_DP_SID) {
 		ret = USB_PD_MUX_DP_ENABLED;
+		pin_assign = mode - TYPEC_STATE_MODAL;
+		if (pin_assign & DP_PIN_ASSIGN_D)
+			ret |= USB_PD_MUX_USB_ENABLED;
+	}
 
 	return ret;
 }