remoteproc: safer boot/shutdown order

Boot the remote processor only after setting up the virtqueues,
and shut it down before deleting them.

Remote processors should obey virtio status changes, and
therefore not manipulate/trigger the virtqueues while the virtio
driver isn't ready, but it's just safer not to rely on that
(plus a vq access might already be inflight while a vdev
status is changed).

We also don't have yet status change notifications, but that's
a temporary limitation.

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Cc: Brian Swetland <swetland@google.com>
Cc: Iliyan Malchev <malchev@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Mark Grosen <mgrosen@ti.com>
Cc: John Williams <john.williams@petalogix.com>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Loic PALLARDY <loic.pallardy@stericsson.com>
Cc: Ludovic BARRE <ludovic.barre@stericsson.com>
Cc: Omar Ramirez Luna <omar.luna@linaro.org>
Cc: Guzman Lugo Fernando <fernando.lugo@ti.com>
Cc: Anna Suman <s-anna@ti.com>
Cc: Clark Rob <rob@ti.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>
Cc: Saravana Kannan <skannan@codeaurora.org>
Cc: David Brown <davidb@codeaurora.org>
Cc: Kieran Bingham <kieranbingham@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>

drivers/remoteproc/remoteproc_virtio.c

@@ -123,14 +123,14 @@ static void rproc_virtio_del_vqs(struct virtio_device *vdev)
 	struct virtqueue *vq, *n;
 	struct rproc *rproc = vdev_to_rproc(vdev);
 
+	/* power down the remote processor before deleting vqs */
+	rproc_shutdown(rproc);
+
 	list_for_each_entry_safe(vq, n, &vdev->vqs, list) {
 		struct rproc_virtio_vq_info *rpvq = vq->priv;
 		vring_del_virtqueue(vq);
 		kfree(rpvq);
 	}
-
-	/* power down the remote processor */
-	rproc_shutdown(rproc);
 }
 
 static int rproc_virtio_find_vqs(struct virtio_device *vdev, unsigned nvqs,
@@ -145,13 +145,6 @@ static int rproc_virtio_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 	if (nvqs != 2)
 		return -EINVAL;
 
-	/* boot the remote processor */
-	ret = rproc_boot(rproc);
-	if (ret) {
-		dev_err(rproc->dev, "rproc_boot() failed %d\n", ret);
-		goto error;
-	}
-
 	for (i = 0; i < nvqs; ++i) {
 		vqs[i] = rp_find_vq(vdev, i, callbacks[i], names[i]);
 		if (IS_ERR(vqs[i])) {
@@ -160,6 +153,13 @@ static int rproc_virtio_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 		}
 	}
 
+	/* now that the vqs are all set, boot the remote processor */
+	ret = rproc_boot(rproc);
+	if (ret) {
+		dev_err(rproc->dev, "rproc_boot() failed %d\n", ret);
+		goto error;
+	}
+
 	return 0;
 
 error: