greybus: control: Add TimeSync get-last-event logic

gb_control_timesync_get_last_event() sends a request asking for the
FrameTime at the last SVC strobe event. The responding entity returns the
FrameTime in the response phase of the request. Performing this operation
to an Interface after previously:

1. Synchronizing time using timesync-enable/timesync-authoritative
2. Sending an SVC_TIMESYNC_PING

will return the FrameTime of the responding entity at the SVC-ping. If
this command is sent before synchronization has been initiated or
successfully completed the responding entity should return an error
code.

- control.c::gb_control_timesync_get_last_event(u64 *frame_time)
  Returns the FrameTime at the last SVC_TIMESYNC_PING to the AP Module.
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/control.c

@@ -177,6 +177,20 @@ int gb_control_timesync_disable(struct gb_control *control)
 				 NULL, 0);
 }
 
+int gb_control_timesync_get_last_event(struct gb_control *control,
+				       u64 *frame_time)
+{
+	struct gb_control_timesync_get_last_event_response response;
+	int ret;
+
+	ret = gb_operation_sync(control->connection,
+				GB_CONTROL_TYPE_TIMESYNC_GET_LAST_EVENT,
+				NULL, 0, &response, sizeof(response));
+	if (!ret)
+		*frame_time = le64_to_cpu(response.frame_time);
+	return ret;
+}
+
 int gb_control_timesync_authoritative(struct gb_control *control,
 				      u64 *frame_time, u8 count)
 {

drivers/staging/greybus/control.h

@@ -43,6 +43,8 @@ int gb_control_get_manifest_operation(struct gb_interface *intf, void *manifest,
 int gb_control_timesync_enable(struct gb_control *control, u8 count,
 			       u64 frame_time, u32 strobe_delay, u32 refclk);
 int gb_control_timesync_disable(struct gb_control *control);
+int gb_control_timesync_get_last_event(struct gb_control *control,
+				       u64 *frame_time);
 int gb_control_timesync_authoritative(struct gb_control *control,
 				      u64 *frame_time, u8 count);
 

drivers/staging/greybus/greybus_protocols.h

@@ -123,6 +123,7 @@ struct gb_protocol_version_response {
 #define GB_CONTROL_TYPE_TIMESYNC_AUTHORITATIVE	0x09
 /*	Unused					0x0a */
 #define GB_CONTROL_TYPE_BUNDLE_VERSION		0x0b
+#define GB_CONTROL_TYPE_TIMESYNC_GET_LAST_EVENT	0x0d
 #define GB_CONTROL_TYPE_MODE_SWITCH		0x0e
 
 struct gb_control_version_request {
@@ -179,6 +180,11 @@ struct gb_control_timesync_authoritative_request {
 } __packed;
 /* timesync authoritative response has no payload */
 
+/* timesync get_last_event_request has no payload */
+struct gb_control_timesync_get_last_event_response {
+	__le64	frame_time;
+} __packed;
+
 /* APBridge protocol */
 
 /* request APB1 log */