In the echo_ping demo, slave send data to master is incrorrect.

[yyl-frank]

I have been troubled by this problem for several days, please help to give some guidance:

I run Linux on A72 as the HOST(master/driver) and FreeRTOS on R5 as a remote(slave/device), A72 send data to R5 is ok, but R5 send data to A72, the data is incorrect.
A72 and R5 source codes come from GitHub, R5 use the rpmsg_echo.c and A72 use the rpmsg_ping.c
If possible, could you please help to explain how buffer is used when R5 send data to A72.
I send data from A72 to R5,it works ok. But I send data from R5 to A72, it doesn’t work.
for example:
I send "ABC" from A72 to R5 and R5 receive "ABC", it's ok. I call rpmsg_send function on R5 side and send "EFG" to A72, but A72 receive data is still "ABC".
create vdev:
On A72: rpdev = platform_create_rpmsg_vdev(platform, 0,VIRTIO_DEV_DRIVER, NULL, rpmsg_name_service_bind_cb);
On R5: rpdev = platform_create_rpmsg_vdev(platform, 0,VIRTIO_DEV_SLAVE,NULL, NULL);

create and init tx and rx virtqueue(master tx equals slave rx, master rx equals slave tx):
host/A72:
rvdev->rvq = vdev->vrings_info[0].vq;
rvdev->svq = vdev->vrings_info[1].vq;
slave/R5:
rvdev->rvq = vdev->vrings_info[1].vq;
rvdev->svq = vdev->vrings_info[0].vq;

In the rpmsg source code(lib/rpmsg/rpmsg_virtio.c):
R5 as slave/remote role, the buffer is not added to the queue, as shown in the following:
128 static int rpmsg_virtio_enqueue_buffer(struct rpmsg_virtio_device rvdev,
129 void buffer, uint32_t len,
130 uint16_t idx)
131 {
132 unsigned int role = rpmsg_virtio_get_role(rvdev);
133
134 #ifdef VIRTIO_CACHED_BUFFERS
135 metal_cache_flush(buffer, len);
136 #endif / VIRTIO_CACHED_BUFFERS /
137
138 #ifndef VIRTIO_DEVICE_ONLY
139 if (role == RPMSG_HOST) {
140 struct virtqueue_buf vqbuf;
141 (void)idx;
142
143 / Initialize buffer node /
144 vqbuf.buf = buffer;
145 vqbuf.len = len;
146 return virtqueue_add_buffer(rvdev->svq, &vqbuf, 1, 0, buffer);
147 }
148 #endif /!VIRTIO_DEVICE_ONLY/
149
150 #ifndef VIRTIO_DRIVER_ONLY
151 if (role == RPMSG_REMOTE) {
152 (void)buffer;
153 return virtqueue_add_consumed_buffer(rvdev->svq, idx, len);
154 }
155 #endif /!VIRTIO_DRIVER_ONLY/
156 return 0;
157 }

[arnopo]

Converted into a discussion, as it does not seem to be an issue but a request for advice
@yyl-frank : does the code without update from you is working?
because seems normal that the rpmsg_echo returns the received pattern: https://github.com/OpenAMP/open-amp/blob/main/apps/examples/echo/rpmsg-echo.c#L45