[PATCH] rpmsg_ns: add synchronization based on component mechanism

[Arnaud Pouliquen]

Implement the component bind mechanism to ensure that the rpmsg virtio bus
driver are probed before treating the first RPMsg.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>
---
 drivers/rpmsg/rpmsg_ns.c         | 26 ++++++++++++-
 drivers/rpmsg/virtio_rpmsg_bus.c | 65 ++++++++++++++++++++++++++++++++
 2 files changed, 89 insertions(+), 2 deletions(-)

diff --git a/drivers/rpmsg/rpmsg_ns.c b/drivers/rpmsg/rpmsg_ns.c
index 5bda7cb44618..057e5d1d29a0 100644
--- a/drivers/rpmsg/rpmsg_ns.c
+++ b/drivers/rpmsg/rpmsg_ns.c
@@ -2,6 +2,7 @@
 /*
  * Copyright (C) STMicroelectronics 2020 - All Rights Reserved
  */
+#include <linux/component.h>
 #include <linux/device.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -55,6 +56,24 @@ static int rpmsg_ns_cb(struct rpmsg_device *rpdev, void *data, int len,
 	return 0;
 }
 
+static int rpmsg_ns_bind(struct device *dev, struct device *master, void *data)
+{
+	dev_info(dev, "rpmsg ns bound\n");
+
+	return 0;
+}
+
+static void rpmsg_ns_unbind(struct device *dev, struct device *master,
+			    void *data)
+{
+	dev_info(dev, "rpmsg ns unbound\n");
+}
+
+static const struct component_ops rpmsg_ns_ops = {
+	.bind = rpmsg_ns_bind,
+	.unbind = rpmsg_ns_unbind,
+};
+
 static int rpmsg_ns_probe(struct rpmsg_device *rpdev)
 {
 	struct rpmsg_endpoint *ns_ept;
@@ -63,6 +82,7 @@ static int rpmsg_ns_probe(struct rpmsg_device *rpdev)
 		.dst = RPMSG_NS_ADDR,
 		.name = "name_service",
 	};
+	int ret;
 
 	/*
 	 * Create the NS announcement service endpoint associated to the RPMsg
@@ -76,7 +96,9 @@ static int rpmsg_ns_probe(struct rpmsg_device *rpdev)
 	}
 	rpdev->ept = ns_ept;
 
-	return 0;
+	ret = component_add(&rpdev->dev, &rpmsg_ns_ops);
+
+	return ret;
 }
 
 static struct rpmsg_driver rpmsg_ns_driver = {
@@ -104,5 +126,5 @@ module_exit(rpmsg_ns_exit);
 
 MODULE_DESCRIPTION("Name service announcement rpmsg Driver");
 MODULE_AUTHOR("Arnaud Pouliquen <arnaud.pouliquen@xxxxxx>");
-MODULE_ALIAS("rpmsg_ns");
+MODULE_ALIAS("rpmsg:rpmsg_ns");
 MODULE_LICENSE("GPL v2");
diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 30ef4a5de4ed..c28aac1295fa 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -11,6 +11,7 @@
 
 #define pr_fmt(fmt) "%s: " fmt, __func__
 
+#include <linux/component.h>
 #include <linux/dma-mapping.h>
 #include <linux/idr.h>
 #include <linux/jiffies.h>
@@ -67,11 +68,16 @@ struct virtproc_info {
 	struct mutex endpoints_lock;
 	wait_queue_head_t sendq;
 	atomic_t sleepers;
+	struct component_match *match;
+	struct completion completed;
+	int bind_status;
 };
 
 /* The feature bitmap for virtio rpmsg */
 #define VIRTIO_RPMSG_F_NS	0 /* RP supports name service notifications */
 
+#define BIND_TIMEOUT_MS 1000
+
 /**
  * struct rpmsg_hdr - common header for all rpmsg messages
  * @src: source address
@@ -768,6 +774,17 @@ static void rpmsg_recv_done(struct virtqueue *rvq)
 	unsigned int len, msgs_received = 0;
 	int err;
 
+	/* Wait for all children to be bound */
+	if (vrp->bind_status) {
+		dev_dbg(dev, "cwait bind\n");
+		if (!wait_for_completion_timeout(&vrp->completed,
+					msecs_to_jiffies(BIND_TIMEOUT_MS)))
+			dev_err(dev, "child device(s) binding timeout\n");
+
+		if (vrp->bind_status)
+			dev_err(dev, "failed to bind RPMsg sub device(s)\n");
+	}
+
 	msg = virtqueue_get_buf(rvq, &len);
 	if (!msg) {
 		dev_err(dev, "uhm, incoming signal, but no used buffer ?\n");
@@ -808,6 +825,39 @@ static void rpmsg_xmit_done(struct virtqueue *svq)
 	wake_up_interruptible(&vrp->sendq);
 }
 
+static int virtio_rpmsg_compare(struct device *dev, void *data)
+{
+	return dev == data;
+}
+
+static void virtio_rpmsg_unbind(struct device *dev)
+{
+	/* undbind all child components */
+	component_unbind_all(dev, NULL);
+}
+
+static int virtio_rpmsg_bind(struct device *dev)
+{
+	struct virtio_device *vdev = dev_to_virtio(dev);
+	struct virtproc_info *vrp = vdev->priv;
+
+	dev_dbg(dev, "Bind virtio rpmsg sub devices\n");
+
+	vdev = container_of(dev, struct virtio_device, dev);
+	vrp->bind_status =  component_bind_all(dev, NULL);
+	if (vrp->bind_status)
+		dev_err(dev, "bind virtio rpmsg failed\n");
+
+	complete(&vrp->completed);
+
+	return vrp->bind_status;
+}
+
+static const struct component_master_ops virtio_rpmsg_cmp_ops = {
+	.bind = virtio_rpmsg_bind,
+	.unbind = virtio_rpmsg_unbind,
+};
+
 static int rpmsg_probe(struct virtio_device *vdev)
 {
 	vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
@@ -892,6 +942,7 @@ static int rpmsg_probe(struct virtio_device *vdev)
 	/* if supported by the remote processor, enable the name service */
 	if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) {
 		vch = kzalloc(sizeof(*vch), GFP_KERNEL);
+
 		if (!vch) {
 			err = -ENOMEM;
 			goto free_coherent;
@@ -911,6 +962,20 @@ static int rpmsg_probe(struct virtio_device *vdev)
 		err = rpmsg_ns_register_device(rpdev_ns);
 		if (err)
 			goto free_coherent;
+		/* register a component associated to the virtio platform */
+		component_match_add_release(&vdev->dev, &vrp->match,
+					    NULL, virtio_rpmsg_compare,
+					    &rpdev_ns->dev);
+
+		vrp->bind_status = -ENXIO;
+		init_completion(&vrp->completed);
+		err = component_master_add_with_match(&vdev->dev,
+						      &virtio_rpmsg_cmp_ops,
+						      vrp->match);
+		if (err) {
+			dev_err(&vdev->dev, "failed to bind virtio rpmsg\n");
+			goto free_coherent;
+		}
 	}
 
 	/*
-- 
2.17.1