greybus: es2: implement flush callback

Implement the flush callback which is called as part of connection tear
down to flush host-device queues and stop any ongoing transfers.

Note that this should be considered an optimisation of sort since if
the CPort is stuck waiting for credit, the CPort is likely still stuck
when we try to send the cport_shutdown request over it after the
callback returns.
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/arpc.h

@@ -80,6 +80,7 @@ struct arpc_response_message {
 #define ARPC_TYPE_CPORT_CONNECTED		0x01
 #define ARPC_TYPE_CPORT_QUIESCE			0x02
 #define ARPC_TYPE_CPORT_CLEAR			0x03
+#define ARPC_TYPE_CPORT_FLUSH			0x04
 
 struct arpc_cport_reset_req {
 	__le16 cport_id;
@@ -99,5 +100,8 @@ struct arpc_cport_clear_req {
 	__le16 cport_id;
 } __packed;
 
+struct arpc_cport_flush_req {
+	__le16 cport_id;
+} __packed;
 
 #endif	/* __ARPC_H */

drivers/staging/greybus/es2.c

@@ -765,6 +765,24 @@ static int es2_cport_connected(struct gb_host_device *hd, u16 cport_id)
 	return 0;
 }
 
+static int es2_cport_flush(struct gb_host_device *hd, u16 cport_id)
+{
+	struct es2_ap_dev *es2 = hd_to_es2(hd);
+	struct device *dev = &es2->usb_dev->dev;
+	struct arpc_cport_flush_req req;
+	int ret;
+
+	req.cport_id = cpu_to_le16(cport_id);
+	ret = arpc_sync(es2, ARPC_TYPE_CPORT_FLUSH, &req, sizeof(req),
+			NULL, ES2_ARPC_CPORT_TIMEOUT);
+	if (ret) {
+		dev_err(dev, "failed to flush cport %u: %d\n", cport_id, ret);
+		return ret;
+	}
+
+	return 0;
+}
+
 static int es2_cport_quiesce(struct gb_host_device *hd, u16 cport_id,
 				size_t peer_space, unsigned int timeout)
 {
@@ -997,6 +1015,7 @@ static struct gb_hd_driver es2_driver = {
 	.cport_enable			= cport_enable,
 	.cport_disable			= cport_disable,
 	.cport_connected		= es2_cport_connected,
+	.cport_flush			= es2_cport_flush,
 	.cport_quiesce			= es2_cport_quiesce,
 	.cport_clear			= es2_cport_clear,
 	.latency_tag_enable		= latency_tag_enable,