remoteproc: Introducing function rproc_actuate()

Introduce function rproc_actuate() that provides the same
functionatlity as rproc_fw_boot(), but without the steps that
involve interaction with the firmware image.  That way we can
deal with scenarios where the remoteproc core is attaching
to a remote processor that has already been started by another
entity.
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Tested-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Link: https://lore.kernel.org/r/20200714195035.1426873-5-mathieu.poirier@linaro.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/remoteproc_core.c

@@ -1372,7 +1372,7 @@ static int rproc_start(struct rproc *rproc, const struct firmware *fw)
 	return ret;
 }
 
-static int __maybe_unused rproc_attach(struct rproc *rproc)
+static int rproc_attach(struct rproc *rproc)
 {
 	struct device *dev = &rproc->dev;
 	int ret;
@@ -1493,6 +1493,63 @@ static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
 	return ret;
 }
 
+/*
+ * Attach to remote processor - similar to rproc_fw_boot() but without
+ * the steps that deal with the firmware image.
+ */
+static int __maybe_unused rproc_actuate(struct rproc *rproc)
+{
+	struct device *dev = &rproc->dev;
+	int ret;
+
+	/*
+	 * if enabling an IOMMU isn't relevant for this rproc, this is
+	 * just a nop
+	 */
+	ret = rproc_enable_iommu(rproc);
+	if (ret) {
+		dev_err(dev, "can't enable iommu: %d\n", ret);
+		return ret;
+	}
+
+	/* reset max_notifyid */
+	rproc->max_notifyid = -1;
+
+	/* reset handled vdev */
+	rproc->nb_vdev = 0;
+
+	/*
+	 * Handle firmware resources required to attach to a remote processor.
+	 * Because we are attaching rather than booting the remote processor,
+	 * we expect the platform driver to properly set rproc->table_ptr.
+	 */
+	ret = rproc_handle_resources(rproc, rproc_loading_handlers);
+	if (ret) {
+		dev_err(dev, "Failed to process resources: %d\n", ret);
+		goto disable_iommu;
+	}
+
+	/* Allocate carveout resources associated to rproc */
+	ret = rproc_alloc_registered_carveouts(rproc);
+	if (ret) {
+		dev_err(dev, "Failed to allocate associated carveouts: %d\n",
+			ret);
+		goto clean_up_resources;
+	}
+
+	ret = rproc_attach(rproc);
+	if (ret)
+		goto clean_up_resources;
+
+	return 0;
+
+clean_up_resources:
+	rproc_resource_cleanup(rproc);
+disable_iommu:
+	rproc_disable_iommu(rproc);
+	return ret;
+}
+
 /*
  * take a firmware and boot it up.
  *