greybus: control: add interface suspend prepare operation

Add the AP implementation for the Greybus Control Interface Suspend
Prepare Operation. AP uses this Operation during the Suspend transition
to request the Interface to enter a low-power mode after it detects a
subsequent UniPro link hibernation.
Signed-off-by: David Lin <dtwlin@google.com>
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Alex Elder <elder@linaro.org>

drivers/staging/greybus/control.c

@@ -348,6 +348,41 @@ int gb_control_bundle_activate(struct gb_control *control, u8 bundle_id)
 	return 0;
 }
 
+static int gb_control_interface_pm_status_map(u8 status)
+{
+	switch (status) {
+	case GB_CONTROL_INTF_PM_BUSY:
+		return -EBUSY;
+	case GB_CONTROL_INTF_PM_NA:
+		return -ENOMSG;
+	default:
+		return -EREMOTEIO;
+	}
+}
+
+int gb_control_interface_suspend_prepare(struct gb_control *control)
+{
+	struct gb_control_intf_pm_response response;
+	int ret;
+
+	ret = gb_operation_sync(control->connection,
+				GB_CONTROL_TYPE_INTF_SUSPEND_PREPARE, NULL, 0,
+				&response, sizeof(response));
+	if (ret) {
+		dev_err(&control->dev,
+			"failed to send interface suspend prepare: %d\n", ret);
+		return ret;
+	}
+
+	if (response.status != GB_CONTROL_INTF_PM_OK) {
+		dev_err(&control->dev, "interface error while preparing suspend: %d\n",
+			response.status);
+		return gb_control_interface_pm_status_map(response.status);
+	}
+
+	return 0;
+}
+
 static ssize_t vendor_string_show(struct device *dev,
 			struct device_attribute *attr, char *buf)
 {

drivers/staging/greybus/control.h

@@ -56,4 +56,5 @@ int gb_control_bundle_suspend(struct gb_control *control, u8 bundle_id);
 int gb_control_bundle_resume(struct gb_control *control, u8 bundle_id);
 int gb_control_bundle_deactivate(struct gb_control *control, u8 bundle_id);
 int gb_control_bundle_activate(struct gb_control *control, u8 bundle_id);
+int gb_control_interface_suspend_prepare(struct gb_control *control);
 #endif /* __CONTROL_H */

drivers/staging/greybus/greybus_protocols.h

@@ -130,6 +130,7 @@ struct gb_protocol_version_response {
 #define GB_CONTROL_TYPE_BUNDLE_RESUME		0x10
 #define GB_CONTROL_TYPE_BUNDLE_DEACTIVATE	0x11
 #define GB_CONTROL_TYPE_BUNDLE_ACTIVATE		0x12
+#define GB_CONTROL_TYPE_INTF_SUSPEND_PREPARE		0x13
 
 struct gb_control_version_request {
 	__u8	major;
@@ -214,6 +215,20 @@ struct gb_control_bundle_pm_response {
 	__u8	status;
 } __packed;
 
+/*
+ * Interface Suspend Prepare and Deactivate Prepare operations use the same
+ * response layout and error codes. Define a single response structure and reuse
+ * it. Both operations have no payload.
+ */
+
+#define GB_CONTROL_INTF_PM_OK		0x00
+#define GB_CONTROL_INTF_PM_BUSY		0x01
+#define GB_CONTROL_INTF_PM_NA		0x02
+
+struct gb_control_intf_pm_response {
+	__u8	status;
+} __packed;
+
 /* APBridge protocol */
 
 /* request APB1 log */