staging: typec: tcpm: Add get_current_limit tcpc_dev callback

A Rp signalling the default current limit indicates that we're possibly
connected to an USB2 power-source. In some cases the type-c port-controller
may provide the capability to detect the current-limit in this case,
through e.g. BC1.2 detection.

This commit adds an optional get_current_limit tcpc_dev callback which
allows the port-controller to provide current-limit detection for when
the CC pin is pulled up with Rp.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/typec/tcpm.c

@@ -685,7 +685,10 @@ static u32 tcpm_get_current_limit(struct tcpm_port *port)
 		break;
 	case TYPEC_CC_RP_DEF:
 	default:
-		limit = 0;
+		if (port->tcpc->get_current_limit)
+			limit = port->tcpc->get_current_limit(port->tcpc);
+		else
+			limit = 0;
 		break;
 	}
 

drivers/staging/typec/tcpm.h

@@ -109,6 +109,13 @@ struct tcpc_dev {
 
 	int (*init)(struct tcpc_dev *dev);
 	int (*get_vbus)(struct tcpc_dev *dev);
+	/*
+	 * This optional callback gets called by the tcpm core when configured
+	 * as a snk and cc=Rp-def. This allows the tcpm to provide a fallback
+	 * current-limit detection method for the cc=Rp-def case. E.g. some
+	 * tcpcs may include BC1.2 charger detection and use that in this case.
+	 */
+	int (*get_current_limit)(struct tcpc_dev *dev);
 	int (*set_cc)(struct tcpc_dev *dev, enum typec_cc_status cc);
 	int (*get_cc)(struct tcpc_dev *dev, enum typec_cc_status *cc1,
 		      enum typec_cc_status *cc2);