remoteproc: virtio: Create platform device for the remoteproc_virtio

Define a platform driver to manage the remoteproc virtio device as
a platform devices.

The platform device allows to pass rproc_vdev_data platform data to
specify properties that are stored in the rproc_vdev structure.

Such approach will allow to preserve legacy remoteproc virtio device
creation but also to probe the device using device tree mechanism.

remoteproc_virtio.c update:
  - Add rproc_virtio_driver platform driver. The probe ops replaces
    the rproc_rvdev_add_device function.
  - All reference to the rvdev->dev has been updated to rvdev-pdev->dev.
  - rproc_rvdev_release is removed as associated to the rvdev device.
  - The use of rvdev->kref counter is replaced by get/put_device on the
    remoteproc virtio platform device.
  - The vdev device no longer increments rproc device counter.
    increment/decrement is done in rproc_virtio_probe/rproc_virtio_remove
    function in charge of the vrings allocation/free.

remoteproc_core.c update:
  Migrate from the rvdev device to the rvdev platform device.
  From this patch, when a vdev resource is found in the resource table
  the remoteproc core register a platform device.
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
Link: https://lore.kernel.org/r/20220921135044.917140-5-arnaud.pouliquen@foss.st.comSigned-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

drivers/remoteproc/remoteproc_core.c

@@ -480,6 +480,7 @@ static int rproc_handle_vdev(struct rproc *rproc, void *ptr,
 	struct rproc_vdev *rvdev;
 	size_t rsc_size;
 	struct rproc_vdev_data rvdev_data;
+	struct platform_device *pdev;
 
 	/* make sure resource isn't truncated */
 	rsc_size = struct_size(rsc, vring, rsc->num_of_vrings);
@@ -508,9 +509,12 @@ static int rproc_handle_vdev(struct rproc *rproc, void *ptr,
 	rvdev_data.rsc_offset = offset;
 	rvdev_data.rsc = rsc;
 
-	rvdev = rproc_rvdev_add_device(rproc, &rvdev_data);
-	if (IS_ERR(rvdev))
-		return PTR_ERR(rvdev);
+	pdev = platform_device_register_data(dev, "rproc-virtio", rvdev_data.index, &rvdev_data,
+					     sizeof(rvdev_data));
+	if (IS_ERR(pdev)) {
+		dev_err(dev, "failed to create rproc-virtio device\n");
+		return PTR_ERR(pdev);
+	}
 
 	return 0;
 }
@@ -1246,7 +1250,7 @@ void rproc_resource_cleanup(struct rproc *rproc)
 
 	/* clean up remote vdev entries */
 	list_for_each_entry_safe(rvdev, rvtmp, &rproc->rvdevs, node)
-		kref_put(&rvdev->refcount, rproc_vdev_release);
+		platform_device_unregister(rvdev->pdev);
 
 	rproc_coredump_cleanup(rproc);
 }

drivers/remoteproc/remoteproc_internal.h

@@ -45,9 +45,7 @@ int rproc_of_parse_firmware(struct device *dev, int index,
 			    const char **fw_name);
 
 /* from remoteproc_virtio.c */
-struct rproc_vdev *rproc_rvdev_add_device(struct rproc *rproc, struct rproc_vdev_data *rvdev_data);
 irqreturn_t rproc_vq_interrupt(struct rproc *rproc, int vq_id);
-void rproc_vdev_release(struct kref *ref);
 
 /* from remoteproc_debugfs.c */
 void rproc_remove_trace_file(struct dentry *tfile);

drivers/remoteproc/remoteproc_virtio.c

@@ -13,6 +13,7 @@
 #include <linux/dma-map-ops.h>
 #include <linux/dma-mapping.h>
 #include <linux/export.h>
+#include <linux/of_platform.h>
 #include <linux/of_reserved_mem.h>
 #include <linux/remoteproc.h>
 #include <linux/virtio.h>
@@ -46,7 +47,11 @@ static int copy_dma_range_map(struct device *to, struct device *from)
 
 static struct rproc_vdev *vdev_to_rvdev(struct virtio_device *vdev)
 {
-	return container_of(vdev->dev.parent, struct rproc_vdev, dev);
+	struct platform_device *pdev;
+
+	pdev = container_of(vdev->dev.parent, struct platform_device, dev);
+
+	return platform_get_drvdata(pdev);
 }
 
 static  struct rproc *vdev_to_rproc(struct virtio_device *vdev)
@@ -343,13 +348,10 @@ static void rproc_virtio_dev_release(struct device *dev)
 {
 	struct virtio_device *vdev = dev_to_virtio(dev);
 	struct rproc_vdev *rvdev = vdev_to_rvdev(vdev);
-	struct rproc *rproc = vdev_to_rproc(vdev);
 
 	kfree(vdev);
 
-	kref_put(&rvdev->refcount, rproc_vdev_release);
-
-	put_device(&rproc->dev);
+	put_device(&rvdev->pdev->dev);
 }
 
 /**
@@ -365,7 +367,7 @@ static void rproc_virtio_dev_release(struct device *dev)
 static int rproc_add_virtio_dev(struct rproc_vdev *rvdev, int id)
 {
 	struct rproc *rproc = rvdev->rproc;
-	struct device *dev = &rvdev->dev;
+	struct device *dev = &rvdev->pdev->dev;
 	struct virtio_device *vdev;
 	struct rproc_mem_entry *mem;
 	int ret;
@@ -435,18 +437,8 @@ static int rproc_add_virtio_dev(struct rproc_vdev *rvdev, int id)
 	vdev->dev.parent = dev;
 	vdev->dev.release = rproc_virtio_dev_release;
 
-	/*
-	 * We're indirectly making a non-temporary copy of the rproc pointer
-	 * here, because drivers probed with this vdev will indirectly
-	 * access the wrapping rproc.
-	 *
-	 * Therefore we must increment the rproc refcount here, and decrement
-	 * it _only_ when the vdev is released.
-	 */
-	get_device(&rproc->dev);
-
 	/* Reference the vdev and vring allocations */
-	kref_get(&rvdev->refcount);
+	get_device(dev);
 
 	ret = register_virtio_device(vdev);
 	if (ret) {
@@ -488,79 +480,57 @@ static int rproc_vdev_do_start(struct rproc_subdev *subdev)
 static void rproc_vdev_do_stop(struct rproc_subdev *subdev, bool crashed)
 {
 	struct rproc_vdev *rvdev = container_of(subdev, struct rproc_vdev, subdev);
+	struct device *dev = &rvdev->pdev->dev;
 	int ret;
 
-	ret = device_for_each_child(&rvdev->dev, NULL, rproc_remove_virtio_dev);
+	ret = device_for_each_child(dev, NULL, rproc_remove_virtio_dev);
 	if (ret)
-		dev_warn(&rvdev->dev, "can't remove vdev child device: %d\n", ret);
-}
-
-/**
- * rproc_rvdev_release() - release the existence of a rvdev
- *
- * @dev: the subdevice's dev
- */
-static void rproc_rvdev_release(struct device *dev)
-{
-	struct rproc_vdev *rvdev = container_of(dev, struct rproc_vdev, dev);
-
-	of_reserved_mem_device_release(dev);
-	dma_release_coherent_memory(dev);
-
-	kfree(rvdev);
+		dev_warn(dev, "can't remove vdev child device: %d\n", ret);
 }
 
-struct rproc_vdev *
-rproc_rvdev_add_device(struct rproc *rproc, struct rproc_vdev_data *rvdev_data)
+static int rproc_virtio_probe(struct platform_device *pdev)
 {
+	struct device *dev = &pdev->dev;
+	struct rproc_vdev_data *rvdev_data = dev->platform_data;
 	struct rproc_vdev *rvdev;
-	struct fw_rsc_vdev *rsc = rvdev_data->rsc;
-	char name[16];
+	struct rproc *rproc = container_of(dev->parent, struct rproc, dev);
+	struct fw_rsc_vdev *rsc;
 	int i, ret;
 
-	rvdev = kzalloc(sizeof(*rvdev), GFP_KERNEL);
-	if (!rvdev)
-		return ERR_PTR(-ENOMEM);
+	if (!rvdev_data)
+		return -EINVAL;
 
-	kref_init(&rvdev->refcount);
+	rvdev = devm_kzalloc(dev, sizeof(*rvdev), GFP_KERNEL);
+	if (!rvdev)
+		return -ENOMEM;
 
 	rvdev->id = rvdev_data->id;
 	rvdev->rproc = rproc;
 	rvdev->index = rvdev_data->index;
 
-	/* Initialise vdev subdevice */
-	snprintf(name, sizeof(name), "vdev%dbuffer", rvdev->index);
-	rvdev->dev.parent = &rproc->dev;
-	rvdev->dev.release = rproc_rvdev_release;
-	dev_set_name(&rvdev->dev, "%s#%s", dev_name(rvdev->dev.parent), name);
-	dev_set_drvdata(&rvdev->dev, rvdev);
-
-	ret = device_register(&rvdev->dev);
-	if (ret) {
-		put_device(&rvdev->dev);
-		return ERR_PTR(ret);
-	}
-
-	ret = copy_dma_range_map(&rvdev->dev, rproc->dev.parent);
+	ret = copy_dma_range_map(dev, rproc->dev.parent);
 	if (ret)
-		goto free_rvdev;
+		return ret;
 
 	/* Make device dma capable by inheriting from parent's capabilities */
-	set_dma_ops(&rvdev->dev, get_dma_ops(rproc->dev.parent));
+	set_dma_ops(dev, get_dma_ops(rproc->dev.parent));
 
-	ret = dma_coerce_mask_and_coherent(&rvdev->dev,
-					   dma_get_mask(rproc->dev.parent));
+	ret = dma_coerce_mask_and_coherent(dev, dma_get_mask(rproc->dev.parent));
 	if (ret) {
-		dev_warn(&rvdev->dev,
-			 "Failed to set DMA mask %llx. Trying to continue... (%pe)\n",
+		dev_warn(dev, "Failed to set DMA mask %llx. Trying to continue... (%pe)\n",
 			 dma_get_mask(rproc->dev.parent), ERR_PTR(ret));
 	}
 
+	platform_set_drvdata(pdev, rvdev);
+	rvdev->pdev = pdev;
+
+	rsc = rvdev_data->rsc;
+
 	/* parse the vrings */
 	for (i = 0; i < rsc->num_of_vrings; i++) {
 		ret = rproc_parse_vring(rvdev, rsc, i);
 		if (ret)
-			goto free_rvdev;
+			return ret;
 	}
 
 	/* remember the resource offset*/
@@ -580,21 +550,30 @@ rproc_rvdev_add_device(struct rproc *rproc, struct rproc_vdev_data *rvdev_data)
 
 	rproc_add_subdev(rproc, &rvdev->subdev);
 
-	return rvdev;
+	/*
+	 * We're indirectly making a non-temporary copy of the rproc pointer
+	 * here, because the platform device or the vdev device will indirectly
+	 * access the wrapping rproc.
+	 *
+	 * Therefore we must increment the rproc refcount here, and decrement
+	 * it _only_ on platform remove.
+	 */
+	get_device(&rproc->dev);
+
+	return 0;
 
 unwind_vring_allocations:
 	for (i--; i >= 0; i--)
 		rproc_free_vring(&rvdev->vring[i]);
-free_rvdev:
-	device_unregister(&rvdev->dev);
-	return ERR_PTR(ret);
+
+	return ret;
 }
 
-void rproc_vdev_release(struct kref *ref)
+static int rproc_virtio_remove(struct platform_device *pdev)
 {
-	struct rproc_vdev *rvdev = container_of(ref, struct rproc_vdev, refcount);
-	struct rproc_vring *rvring;
+	struct rproc_vdev *rvdev = dev_get_drvdata(&pdev->dev);
 	struct rproc *rproc = rvdev->rproc;
+	struct rproc_vring *rvring;
 	int id;
 
 	for (id = 0; id < ARRAY_SIZE(rvdev->vring); id++) {
@@ -604,5 +583,27 @@ void rproc_vdev_release(struct kref *ref)
 
 	rproc_remove_subdev(rproc, &rvdev->subdev);
 	rproc_remove_rvdev(rvdev);
-	device_unregister(&rvdev->dev);
+
+	of_reserved_mem_device_release(&pdev->dev);
+	dma_release_coherent_memory(&pdev->dev);
+
+	put_device(&rproc->dev);
+
+	return 0;
 }
+
+/* Platform driver */
+static const struct of_device_id rproc_virtio_match[] = {
+	{ .compatible = "virtio,rproc" },
+	{},
+};
+
+static struct platform_driver rproc_virtio_driver = {
+	.probe		= rproc_virtio_probe,
+	.remove		= rproc_virtio_remove,
+	.driver		= {
+		.name	= "rproc-virtio",
+		.of_match_table	= rproc_virtio_match,
+	},
+};
+builtin_platform_driver(rproc_virtio_driver);

include/linux/remoteproc.h

@@ -616,9 +616,8 @@ struct rproc_vring {
 
 /**
  * struct rproc_vdev - remoteproc state for a supported virtio device
- * @refcount: reference counter for the vdev and vring allocations
  * @subdev: handle for registering the vdev as a rproc subdevice
- * @dev: device struct used for reference count semantics
+ * @pdev: remoteproc virtio platform device
  * @id: virtio device id (as in virtio_ids.h)
  * @node: list node
  * @rproc: the rproc handle
@@ -627,10 +626,9 @@ struct rproc_vring {
  * @index: vdev position versus other vdev declared in resource table
  */
 struct rproc_vdev {
-	struct kref refcount;
 
 	struct rproc_subdev subdev;
-	struct device dev;
+	struct platform_device *pdev;
 
 	unsigned int id;
 	struct list_head node;