platform/chrome: cros_typec_switch: Set EC retimer

Invoke ChromeOS EC host commands to set EC-controlled retimer switches
to the state the Type-C framework instructs.
Signed-off-by: Prashant Malani <pmalani@chromium.org>
Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220816214857.2088914-4-pmalani@chromium.org

drivers/platform/chrome/cros_typec_switch.c

@@ -9,7 +9,10 @@
 #include <linux/acpi.h>
 #include <linux/module.h>
 #include <linux/platform_data/cros_ec_commands.h>
+#include <linux/platform_data/cros_ec_proto.h>
 #include <linux/platform_device.h>
+#include <linux/usb/typec_altmode.h>
+#include <linux/usb/typec_dp.h>
 #include <linux/usb/typec_retimer.h>
 
 #define DRV_NAME "cros-typec-switch"
@@ -28,9 +31,57 @@ struct cros_typec_switch_data {
 	struct cros_typec_port *ports[EC_USB_PD_MAX_PORTS];
 };
 
+static int cros_typec_cmd_mux_set(struct cros_typec_switch_data *sdata, int port_num, u8 index,
+				  u8 state)
+{
+	struct ec_params_typec_control req = {
+		.port = port_num,
+		.command = TYPEC_CONTROL_COMMAND_USB_MUX_SET,
+		.mux_params = {
+			.mux_index = index,
+			.mux_flags = state,
+		},
+	};
+
+	return cros_ec_cmd(sdata->ec, 0, EC_CMD_TYPEC_CONTROL, &req, sizeof(req), NULL, 0);
+}
+
+static int cros_typec_get_mux_state(unsigned long mode, struct typec_altmode *alt)
+{
+	int ret = -EOPNOTSUPP;
+
+	if (mode == TYPEC_STATE_SAFE)
+		ret = USB_PD_MUX_SAFE_MODE;
+	else if (mode == TYPEC_STATE_USB)
+		ret = USB_PD_MUX_USB_ENABLED;
+	else if (alt && alt->svid == USB_TYPEC_DP_SID)
+		ret = USB_PD_MUX_DP_ENABLED;
+
+	return ret;
+}
+
+/*
+ * The ChromeOS EC treats both mode-switches and retimers as "muxes" for the purposes of the
+ * host command API. This common function configures and verifies the retimer/mode-switch
+ * according to the provided setting.
+ */
+static int cros_typec_configure_mux(struct cros_typec_switch_data *sdata, int port_num, int index,
+				    unsigned long mode, struct typec_altmode *alt)
+{
+	int ret = cros_typec_get_mux_state(mode, alt);
+
+	if (ret < 0)
+		return ret;
+
+	return cros_typec_cmd_mux_set(sdata, port_num, index, (u8)ret);
+}
+
 static int cros_typec_retimer_set(struct typec_retimer *retimer, struct typec_retimer_state *state)
 {
-	return 0;
+	struct cros_typec_port *port = typec_retimer_get_drvdata(retimer);
+
+	/* Retimers have index 1. */
+	return cros_typec_configure_mux(port->sdata, port->port_num, 1, state->mode, state->alt);
 }
 
 static void cros_typec_unregister_switches(struct cros_typec_switch_data *sdata)