dax/hmem: Convey the dax range via memregion_info()

In preparation for hmem platform devices to be unregistered, stop using
platform_device_add_resources() to convey the address range. The
platform_device_add_resources() API causes an existing "Soft Reserved"
iomem resource to be re-parented under an inserted platform device
resource. When that platform device is deleted it removes the platform
device resource and all children.

Instead, it is sufficient to convey just the address range and let
request_mem_region() insert resources to indicate the devices active in
the range. This allows the "Soft Reserved" resource to be re-enumerated
upon the next probe event.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/167602002217.1924368.7036275892522551624.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/dax/hmem/device.c

@@ -15,71 +15,62 @@ static struct resource hmem_active = {
 	.flags = IORESOURCE_MEM,
 };
 
-void hmem_register_device(int target_nid, struct resource *r)
+void hmem_register_device(int target_nid, struct resource *res)
 {
-	/* define a clean / non-busy resource for the platform device */
-	struct resource res = {
-		.start = r->start,
-		.end = r->end,
-		.flags = IORESOURCE_MEM,
-		.desc = IORES_DESC_SOFT_RESERVED,
-	};
 	struct platform_device *pdev;
 	struct memregion_info info;
 	int rc, id;
 
 	if (nohmem)
 		return;
 
-	rc = region_intersects(res.start, resource_size(&res), IORESOURCE_MEM,
-			IORES_DESC_SOFT_RESERVED);
+	rc = region_intersects(res->start, resource_size(res), IORESOURCE_MEM,
+			       IORES_DESC_SOFT_RESERVED);
 	if (rc != REGION_INTERSECTS)
 		return;
 
 	id = memregion_alloc(GFP_KERNEL);
 	if (id < 0) {
-		pr_err("memregion allocation failure for %pr\n", &res);
+		pr_err("memregion allocation failure for %pr\n", res);
 		return;
 	}
 
 	pdev = platform_device_alloc("hmem", id);
 	if (!pdev) {
-		pr_err("hmem device allocation failure for %pr\n", &res);
+		pr_err("hmem device allocation failure for %pr\n", res);
 		goto out_pdev;
 	}
 
-	if (!__request_region(&hmem_active, res.start, resource_size(&res),
+	if (!__request_region(&hmem_active, res->start, resource_size(res),
 			      dev_name(&pdev->dev), 0)) {
-		dev_dbg(&pdev->dev, "hmem range %pr already active\n", &res);
+		dev_dbg(&pdev->dev, "hmem range %pr already active\n", res);
 		goto out_active;
 	}
 
 	pdev->dev.numa_node = numa_map_to_online_node(target_nid);
 	info = (struct memregion_info) {
 		.target_node = target_nid,
+		.range = {
+			.start = res->start,
+			.end = res->end,
+		},
 	};
 	rc = platform_device_add_data(pdev, &info, sizeof(info));
 	if (rc < 0) {
-		pr_err("hmem memregion_info allocation failure for %pr\n", &res);
-		goto out_resource;
-	}
-
-	rc = platform_device_add_resources(pdev, &res, 1);
-	if (rc < 0) {
-		pr_err("hmem resource allocation failure for %pr\n", &res);
+		pr_err("hmem memregion_info allocation failure for %pr\n", res);
 		goto out_resource;
 	}
 
 	rc = platform_device_add(pdev);
 	if (rc < 0) {
-		dev_err(&pdev->dev, "device add failed for %pr\n", &res);
+		dev_err(&pdev->dev, "device add failed for %pr\n", res);
 		goto out_resource;
 	}
 
 	return;
 
 out_resource:
-	__release_region(&hmem_active, res.start, resource_size(&res));
+	__release_region(&hmem_active, res->start, resource_size(res));
 out_active:
 	platform_device_put(pdev);
 out_pdev:

drivers/dax/hmem/hmem.c

@@ -15,25 +15,17 @@ static int dax_hmem_probe(struct platform_device *pdev)
 	struct memregion_info *mri;
 	struct dev_dax_data data;
 	struct dev_dax *dev_dax;
-	struct resource *res;
-	struct range range;
-
-	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	if (!res)
-		return -ENOMEM;
 
 	mri = dev->platform_data;
-	range.start = res->start;
-	range.end = res->end;
-	dax_region = alloc_dax_region(dev, pdev->id, &range, mri->target_node,
-			PMD_SIZE, 0);
+	dax_region = alloc_dax_region(dev, pdev->id, &mri->range,
+				      mri->target_node, PMD_SIZE, 0);
 	if (!dax_region)
 		return -ENOMEM;
 
 	data = (struct dev_dax_data) {
 		.dax_region = dax_region,
 		.id = -1,
-		.size = region_idle ? 0 : resource_size(res),
+		.size = region_idle ? 0 : range_len(&mri->range),
 	};
 	dev_dax = devm_create_dev_dax(&data);
 	if (IS_ERR(dev_dax))

include/linux/memregion.h

@@ -3,10 +3,12 @@
 #define _MEMREGION_H_
 #include <linux/types.h>
 #include <linux/errno.h>
+#include <linux/range.h>
 #include <linux/bug.h>
 
 struct memregion_info {
 	int target_node;
+	struct range range;
 };
 
 #ifdef CONFIG_MEMREGION