[RFC PATCH 07/10] rpmsg: virtio: Implement the set_flow_control ops

[Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>]

Add the capability for a rpmsg local endpoint to informs the
remote of its state using the flow control channel.

If the feature is not supported by the remote processor, no
message is sent.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
---
 drivers/rpmsg/virtio_rpmsg_bus.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 40d2ab86b395..96bd12095c8c 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -154,6 +154,8 @@ static ssize_t virtio_rpmsg_get_mtu(struct rpmsg_endpoint *ept);
 static struct rpmsg_device *__rpmsg_create_channel(struct virtproc_info *vrp,
 						   struct rpmsg_channel_info *chinfo);
 
+static int virtio_rpmsg_set_flow_control(struct rpmsg_endpoint *ept, bool enable);
+
 static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
 	.destroy_ept = virtio_rpmsg_destroy_ept,
 	.send = virtio_rpmsg_send,
@@ -163,6 +165,7 @@ static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
 	.trysendto = virtio_rpmsg_trysendto,
 	.trysend_offchannel = virtio_rpmsg_trysend_offchannel,
 	.get_mtu = virtio_rpmsg_get_mtu,
+	.set_flow_control = virtio_rpmsg_set_flow_control,
 };
 
 /**
@@ -745,6 +748,34 @@ static ssize_t virtio_rpmsg_get_mtu(struct rpmsg_endpoint *ept)
 	return vch->vrp->buf_size - sizeof(struct rpmsg_hdr);
 }
 
+static int virtio_rpmsg_set_flow_control(struct rpmsg_endpoint *ept, bool enable)
+{
+	struct rpmsg_device *rpdev;
+	struct virtio_rpmsg_channel *vch;
+	int err = 0;
+
+	if (!ept)
+		return -EINVAL;
+
+	rpdev = ept->rpdev;
+	vch = to_virtio_rpmsg_channel(rpdev);
+
+	if (virtio_has_feature(vch->vrp->vdev, VIRTIO_RPMSG_F_FC)) {
+		struct rpmsg_ept_msg msg;
+
+		msg.src = cpu_to_rpmsg32(rpdev, ept->addr);
+		msg.dst = cpu_to_rpmsg32(rpdev, rpdev->dst);
+		msg.flags = cpu_to_rpmsg32(rpdev, enable ? RPMSG_EPT_FC_ON : 0);
+
+		err = rpmsg_sendto(ept, &msg, sizeof(msg), RPMSG_FC_ADDR);
+		if (err)
+			dev_err(&rpdev->dev, "Failed to set endpoint 0x%x state %sable (%d)\n",
+				ept->addr, enable ? "en" : "dis", err);
+	}
+
+	return err;
+}
+
 static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
 			     struct rpmsg_hdr *msg, unsigned int len)
 {
-- 
2.25.1