openamp: Introduce cache helpers

To manage shared vring memory behind caches.

Signed-off-by: Carlo Caione <ccaione@baylibre.com>

lib/rpmsg/rpmsg_virtio.c

@@ -8,6 +8,7 @@
  */
 
 #include <metal/alloc.h>
+#include <metal/cache.h>
 #include <metal/sleep.h>
 #include <metal/utilities.h>
 #include <openamp/rpmsg_virtio.h>
@@ -102,6 +103,11 @@ static int rpmsg_virtio_enqueue_buffer(struct rpmsg_virtio_device *rvdev,
 				       uint16_t idx)
 {
 	unsigned int role = rpmsg_virtio_get_role(rvdev);
+
+#ifdef VIRTIO_CACHED_BUFFERS
+	metal_cache_flush(buffer, len);
+#endif /* VIRTIO_CACHED_BUFFERS */
+
 #ifndef VIRTIO_SLAVE_ONLY
 	if (role == RPMSG_MASTER) {
 		struct virtqueue_buf vqbuf;
@@ -192,6 +198,11 @@ static void *rpmsg_virtio_get_rx_buffer(struct rpmsg_virtio_device *rvdev,
 	}
 #endif /*!VIRTIO_MASTER_ONLY*/
 
+#ifdef VIRTIO_CACHED_BUFFERS
+	/* Invalidate the buffer before returning it */
+	metal_cache_invalidate(data, *len);
+#endif /* VIRTIO_CACHED_BUFFERS */
+
 	return data;
 }