remoteproc: Refactor rproc module locking

Lock the implementation as we hand out references to client drivers
rather than when they try to boot the remote processor. This allows
auto-booting remote processors to be shut down by unloading their
module, in addition to first unbinding them.
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/remoteproc_core.c

@@ -1035,13 +1035,6 @@ static int __rproc_boot(struct rproc *rproc, bool wait)
 		return ret;
 	}
 
-	/* prevent underlying implementation from being removed */
-	if (!try_module_get(dev->parent->driver->owner)) {
-		dev_err(dev, "%s: can't get owner\n", __func__);
-		ret = -EINVAL;
-		goto unlock_mutex;
-	}
-
 	/* skip the boot process if rproc is already powered up */
 	if (atomic_inc_return(&rproc->power) > 1) {
 		ret = 0;
@@ -1066,10 +1059,8 @@ static int __rproc_boot(struct rproc *rproc, bool wait)
 	release_firmware(firmware_p);
 
 downref_rproc:
-	if (ret) {
-		module_put(dev->parent->driver->owner);
+	if (ret)
 		atomic_dec(&rproc->power);
-	}
 unlock_mutex:
 	mutex_unlock(&rproc->lock);
 	return ret;
@@ -1158,8 +1149,6 @@ void rproc_shutdown(struct rproc *rproc)
 
 out:
 	mutex_unlock(&rproc->lock);
-	if (!ret)
-		module_put(dev->parent->driver->owner);
 }
 EXPORT_SYMBOL(rproc_shutdown);
 
@@ -1188,6 +1177,12 @@ struct rproc *rproc_get_by_phandle(phandle phandle)
 	mutex_lock(&rproc_list_mutex);
 	list_for_each_entry(r, &rproc_list, node) {
 		if (r->dev.parent && r->dev.parent->of_node == np) {
+			/* prevent underlying implementation from being removed */
+			if (!try_module_get(r->dev.parent->driver->owner)) {
+				dev_err(&r->dev, "can't get owner\n");
+				break;
+			}
+
 			rproc = r;
 			get_device(&rproc->dev);
 			break;
@@ -1411,6 +1406,7 @@ EXPORT_SYMBOL(rproc_free);
  */
 void rproc_put(struct rproc *rproc)
 {
+	module_put(rproc->dev.parent->driver->owner);
 	put_device(&rproc->dev);
 }
 EXPORT_SYMBOL(rproc_put);