greybus: hd/es2: add cport_quiesce callback and ARPC

Add a host-device cport_quiesce callback, which will be called as part
of the new connection tear-down sequence to disable flow control after
first making sure that enough peer buffer space is available for the
next messages about to be sent.
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Sandeep Patil <sspatil@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/arpc.h

@@ -78,6 +78,7 @@ struct arpc_response_message {
 /* ARPC requests */
 #define ARPC_TYPE_CPORT_RESET			0x00
 #define ARPC_TYPE_CPORT_CONNECTED		0x01
+#define ARPC_TYPE_CPORT_QUIESCE			0x02
 
 struct arpc_cport_reset_req {
 	__le16 cport_id;
@@ -87,5 +88,11 @@ struct arpc_cport_connected_req {
 	__le16 cport_id;
 } __packed;
 
+struct arpc_cport_quiesce_req {
+	__le16 cport_id;
+	__le16 peer_space;
+	__le16 timeout;
+} __packed;
+
 
 #endif	/* __ARPC_H */

drivers/staging/greybus/es2.c

@@ -765,6 +765,35 @@ static int es2_cport_connected(struct gb_host_device *hd, u16 cport_id)
 	return 0;
 }
 
+static int es2_cport_quiesce(struct gb_host_device *hd, u16 cport_id,
+				size_t peer_space, unsigned int timeout)
+{
+	struct es2_ap_dev *es2 = hd_to_es2(hd);
+	struct device *dev = &es2->usb_dev->dev;
+	struct arpc_cport_quiesce_req req;
+	int result;
+	int ret;
+
+	if (peer_space > U16_MAX)
+		return -EINVAL;
+
+	if (timeout > U16_MAX)
+		return -EINVAL;
+
+	req.cport_id = cpu_to_le16(cport_id);
+	req.peer_space = cpu_to_le16(peer_space);
+	req.timeout = cpu_to_le16(timeout);
+	ret = arpc_sync(es2, ARPC_TYPE_CPORT_QUIESCE, &req, sizeof(req),
+			&result, ES2_ARPC_CPORT_TIMEOUT + timeout);
+	if (ret) {
+		dev_err(dev, "failed to quiesce cport %u: %d (%d)\n",
+				cport_id, ret, result);
+		return ret;
+	}
+
+	return 0;
+}
+
 static int latency_tag_enable(struct gb_host_device *hd, u16 cport_id)
 {
 	int retval;
@@ -950,6 +979,7 @@ static struct gb_hd_driver es2_driver = {
 	.cport_enable			= cport_enable,
 	.cport_disable			= cport_disable,
 	.cport_connected		= es2_cport_connected,
+	.cport_quiesce			= es2_cport_quiesce,
 	.latency_tag_enable		= latency_tag_enable,
 	.latency_tag_disable		= latency_tag_disable,
 	.output				= output,

drivers/staging/greybus/hd.h

@@ -25,6 +25,8 @@ struct gb_hd_driver {
 	int (*cport_connected)(struct gb_host_device *hd, u16 cport_id);
 	int (*cport_flush)(struct gb_host_device *hd, u16 cport_id);
 	int (*cport_ping)(struct gb_host_device *hd, u16 cport_id);
+	int (*cport_quiesce)(struct gb_host_device *hd, u16 cport_id,
+				size_t peer_space, unsigned int timeout);
 	int (*message_send)(struct gb_host_device *hd, u16 dest_cport_id,
 			struct gb_message *message, gfp_t gfp_mask);
 	void (*message_cancel)(struct gb_message *message);