libnvdimm: Add device-tree based driver

This patch adds peliminary device-tree bindings for persistent memory
regions. The driver registers a libnvdimm bus for each pmem-region
node and each address range under the node is converted to a region
within that bus.
Signed-off-by: NOliver O'Halloran <oohall@gmail.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

MAINTAINERS

@@ -8035,6 +8035,13 @@ Q:	https://patchwork.kernel.org/project/linux-nvdimm/list/
 S:	Supported
 F:	drivers/nvdimm/pmem*
 
+LIBNVDIMM: DEVICETREE BINDINGS
+M:	Oliver O'Halloran <oohall@gmail.com>
+L:	linux-nvdimm@lists.01.org
+Q:	https://patchwork.kernel.org/project/linux-nvdimm/list/
+S:	Supported
+F:	drivers/nvdimm/of_pmem.c
+
 LIBNVDIMM: NON-VOLATILE MEMORY DEVICE SUBSYSTEM
 M:	Dan Williams <dan.j.williams@intel.com>
 L:	linux-nvdimm@lists.01.org

drivers/nvdimm/Kconfig

@@ -102,4 +102,14 @@ config NVDIMM_DAX
 
 	  Select Y if unsure
 
+config OF_PMEM
+	tristate "Device-tree support for persistent memory regions"
+	depends on OF
+	default LIBNVDIMM
+	help
+	  Allows regions of persistent memory to be described in the
+	  device-tree.
+
+	  Select Y if unsure.
+
 endif

drivers/nvdimm/Makefile

@@ -4,6 +4,7 @@ obj-$(CONFIG_BLK_DEV_PMEM) += nd_pmem.o
 obj-$(CONFIG_ND_BTT) += nd_btt.o
 obj-$(CONFIG_ND_BLK) += nd_blk.o
 obj-$(CONFIG_X86_PMEM_LEGACY) += nd_e820.o
+obj-$(CONFIG_OF_PMEM) += of_pmem.o
 
 nd_pmem-y := pmem.o
 

drivers/nvdimm/of_pmem.c

+// SPDX-License-Identifier: GPL-2.0+
+
+#define pr_fmt(fmt) "of_pmem: " fmt
+
+#include <linux/of_platform.h>
+#include <linux/of_address.h>
+#include <linux/libnvdimm.h>
+#include <linux/module.h>
+#include <linux/ioport.h>
+#include <linux/slab.h>
+
+static const struct attribute_group *region_attr_groups[] = {
+	&nd_region_attribute_group,
+	&nd_device_attribute_group,
+	NULL,
+};
+
+static const struct attribute_group *bus_attr_groups[] = {
+	&nvdimm_bus_attribute_group,
+	NULL,
+};
+
+struct of_pmem_private {
+	struct nvdimm_bus_descriptor bus_desc;
+	struct nvdimm_bus *bus;
+};
+
+static int of_pmem_region_probe(struct platform_device *pdev)
+{
+	struct of_pmem_private *priv;
+	struct device_node *np;
+	struct nvdimm_bus *bus;
+	bool is_volatile;
+	int i;
+
+	np = dev_of_node(&pdev->dev);
+	if (!np)
+		return -ENXIO;
+
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->bus_desc.attr_groups = bus_attr_groups;
+	priv->bus_desc.provider_name = "of_pmem";
+	priv->bus_desc.module = THIS_MODULE;
+	priv->bus_desc.of_node = np;
+
+	priv->bus = bus = nvdimm_bus_register(&pdev->dev, &priv->bus_desc);
+	if (!bus) {
+		kfree(priv);
+		return -ENODEV;
+	}
+	platform_set_drvdata(pdev, priv);
+
+	is_volatile = !!of_find_property(np, "volatile", NULL);
+	dev_dbg(&pdev->dev, "Registering %s regions from %pOF\n",
+			is_volatile ? "volatile" : "non-volatile",  np);
+
+	for (i = 0; i < pdev->num_resources; i++) {
+		struct nd_region_desc ndr_desc;
+		struct nd_region *region;
+
+		/*
+		 * NB: libnvdimm copies the data from ndr_desc into it's own
+		 * structures so passing a stack pointer is fine.
+		 */
+		memset(&ndr_desc, 0, sizeof(ndr_desc));
+		ndr_desc.attr_groups = region_attr_groups;
+		ndr_desc.numa_node = of_node_to_nid(np);
+		ndr_desc.res = &pdev->resource[i];
+		ndr_desc.of_node = np;
+		set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
+
+		if (is_volatile)
+			region = nvdimm_volatile_region_create(bus, &ndr_desc);
+		else
+			region = nvdimm_pmem_region_create(bus, &ndr_desc);
+
+		if (!region)
+			dev_warn(&pdev->dev, "Unable to register region %pR from %pOF\n",
+					ndr_desc.res, np);
+		else
+			dev_dbg(&pdev->dev, "Registered region %pR from %pOF\n",
+					ndr_desc.res, np);
+	}
+
+	return 0;
+}
+
+static int of_pmem_region_remove(struct platform_device *pdev)
+{
+	struct of_pmem_private *priv = platform_get_drvdata(pdev);
+
+	nvdimm_bus_unregister(priv->bus);
+	kfree(priv);
+
+	return 0;
+}
+
+static const struct of_device_id of_pmem_region_match[] = {
+	{ .compatible = "pmem-region" },
+	{ },
+};
+
+static struct platform_driver of_pmem_region_driver = {
+	.probe = of_pmem_region_probe,
+	.remove = of_pmem_region_remove,
+	.driver = {
+		.name = "of_pmem",
+		.owner = THIS_MODULE,
+		.of_match_table = of_pmem_region_match,
+	},
+};
+
+module_platform_driver(of_pmem_region_driver);
+MODULE_DEVICE_TABLE(of, of_pmem_region_match);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("IBM Corporation");