rpmsg: rpmsg_virtio: fix API to get rx buf

New virtio feature allows to configure rpmsg single buffer size via
virtio device config space. Hence, rx buffer size can be provided by
vdev device config space as well. If failed to calculate rx buf size
using vq descriptor, and rx buf size is available in the config space,
then use it from there.

Signed-off-by: Tanmay Shah <tanmay.shah@amd.com>

Author: tnmysh

lib/include/openamp/rpmsg_virtio.h

@@ -64,8 +64,10 @@ struct rpmsg_virtio_shm_pool {
 METAL_PACKED_BEGIN
 struct rpmsg_virtio_config {
 	/** version of this struct */
-	uint16_t version;
+	uint8_t version;
 
+	/** size of the config space */
+	uint16_t size;
 	/** The size of the buffer used to send data from host to remote */
 	uint32_t h2r_buf_size;
 

lib/rpmsg/rpmsg_virtio.c

@@ -743,7 +743,8 @@ int rpmsg_virtio_get_tx_buffer_size(struct rpmsg_device *rdev)
 int rpmsg_virtio_get_rx_buffer_size(struct rpmsg_device *rdev)
 {
 	struct rpmsg_virtio_device *rvdev;
-	int size = 0;
+	int size = 0, ret;
+	uint32_t features = 0;
 
 	if (!rdev)
 		return RPMSG_ERR_PARAM;
@@ -763,9 +764,22 @@ int rpmsg_virtio_get_rx_buffer_size(struct rpmsg_device *rdev)
 		/*
 		 * If other core is host then buffers are provided by it,
 		 * so get the buffer size from the virtqueue.
+		 * If virtio device has BUFSZ feature, then the rx buffer is
+		 * provided by the vdev config space in the resource table.
 		 */
-		size = (int)virtqueue_get_desc_size(rvdev->rvq) -
-		       sizeof(struct rpmsg_hdr);
+		features = 0;
+		ret = virtio_get_features(rvdev->vdev, &features);
+		if (ret) {
+			metal_mutex_release(&rdev->lock);
+			return RPMSG_ERR_DEV_STATE;
+		}
+
+		if (features & (1 << VIRTIO_RPMSG_F_BUFSZ)) {
+			size = rvdev->config.r2h_buf_size - sizeof(struct rpmsg_hdr);
+		} else {
+			size = (int)virtqueue_get_desc_size(rvdev->rvq) -
+				sizeof(struct rpmsg_hdr);
+		}
 	}
 
 	if (size <= 0)
@@ -831,6 +845,13 @@ int rpmsg_init_vdev_with_config(struct rpmsg_virtio_device *rvdev,
 	}
 
 	if (VIRTIO_ROLE_IS_DEVICE(vdev)) {
+		status = virtio_get_features(vdev, &features);
+		if (status)
+			return status;
+
+		if (features & (1 << VIRTIO_RPMSG_F_BUFSZ))
+			rvdev->config = *config;
+
 		/* wait synchro with the host */
 		status = rpmsg_virtio_wait_remote_ready(rvdev);
 		if (status)