acpi, nfit: add dimm device notification support

Per "ACPI 6.1 Section 9.20.3" NVDIMM devices, children of the ACPI0012
NVDIMM Root device, can receive health event notifications.

Given that these devices are precluded from registering a notification
handler via acpi_driver.acpi_device_ops (due to no _HID), we use
acpi_install_notify_handler() directly.  The registered handler,
acpi_nvdimm_notify(), triggers a poll(2) event on the nmemX/nfit/flags
sysfs attribute when a health event notification is received.

Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/acpi/nfit/core.c

@@ -1248,6 +1248,43 @@ static struct nvdimm *acpi_nfit_dimm_by_handle(struct acpi_nfit_desc *acpi_desc,
 	return NULL;
 }
 
+static void __acpi_nvdimm_notify(struct device *dev, u32 event)
+{
+	struct nfit_mem *nfit_mem;
+	struct acpi_nfit_desc *acpi_desc;
+
+	dev_dbg(dev->parent, "%s: %s: event: %d\n", dev_name(dev), __func__,
+			event);
+
+	if (event != NFIT_NOTIFY_DIMM_HEALTH) {
+		dev_dbg(dev->parent, "%s: unknown event: %d\n", dev_name(dev),
+				event);
+		return;
+	}
+
+	acpi_desc = dev_get_drvdata(dev->parent);
+	if (!acpi_desc)
+		return;
+
+	/*
+	 * If we successfully retrieved acpi_desc, then we know nfit_mem data
+	 * is still valid.
+	 */
+	nfit_mem = dev_get_drvdata(dev);
+	if (nfit_mem && nfit_mem->flags_attr)
+		sysfs_notify_dirent(nfit_mem->flags_attr);
+}
+
+static void acpi_nvdimm_notify(acpi_handle handle, u32 event, void *data)
+{
+	struct acpi_device *adev = data;
+	struct device *dev = &adev->dev;
+
+	device_lock(dev->parent);
+	__acpi_nvdimm_notify(dev, event);
+	device_unlock(dev->parent);
+}
+
 static int acpi_nfit_add_dimm(struct acpi_nfit_desc *acpi_desc,
 		struct nfit_mem *nfit_mem, u32 device_handle)
 {
@@ -1272,6 +1309,13 @@ static int acpi_nfit_add_dimm(struct acpi_nfit_desc *acpi_desc,
 		return force_enable_dimms ? 0 : -ENODEV;
 	}
 
+	if (ACPI_FAILURE(acpi_install_notify_handler(adev_dimm->handle,
+		ACPI_DEVICE_NOTIFY, acpi_nvdimm_notify, adev_dimm))) {
+		dev_err(dev, "%s: notification registration failed\n",
+				dev_name(&adev_dimm->dev));
+		return -ENXIO;
+	}
+
 	/*
 	 * Until standardization materializes we need to consider 4
 	 * different command sets.  Note, that checking for function0 (bit0)
@@ -1310,18 +1354,38 @@ static int acpi_nfit_add_dimm(struct acpi_nfit_desc *acpi_desc,
 	return 0;
 }
 
+static void shutdown_dimm_notify(void *data)
+{
+	struct acpi_nfit_desc *acpi_desc = data;
+	struct nfit_mem *nfit_mem;
+
+	mutex_lock(&acpi_desc->init_mutex);
+	/*
+	 * Clear out the nfit_mem->flags_attr and shut down dimm event
+	 * notifications.
+	 */
+	list_for_each_entry(nfit_mem, &acpi_desc->dimms, list) {
+		if (nfit_mem->flags_attr) {
+			sysfs_put(nfit_mem->flags_attr);
+			nfit_mem->flags_attr = NULL;
+		}
+		acpi_remove_notify_handler(nfit_mem->adev->handle,
+				ACPI_DEVICE_NOTIFY, acpi_nvdimm_notify);
+	}
+	mutex_unlock(&acpi_desc->init_mutex);
+}
+
 static int acpi_nfit_register_dimms(struct acpi_nfit_desc *acpi_desc)
 {
 	struct nfit_mem *nfit_mem;
-	int dimm_count = 0;
+	int dimm_count = 0, rc;
+	struct nvdimm *nvdimm;
 
 	list_for_each_entry(nfit_mem, &acpi_desc->dimms, list) {
 		struct acpi_nfit_flush_address *flush;
 		unsigned long flags = 0, cmd_mask;
-		struct nvdimm *nvdimm;
 		u32 device_handle;
 		u16 mem_flags;
-		int rc;
 
 		device_handle = __to_nfit_memdev(nfit_mem)->device_handle;
 		nvdimm = acpi_nfit_dimm_by_handle(acpi_desc, device_handle);
@@ -1374,7 +1438,30 @@ static int acpi_nfit_register_dimms(struct acpi_nfit_desc *acpi_desc)
 
 	}
 
-	return nvdimm_bus_check_dimm_count(acpi_desc->nvdimm_bus, dimm_count);
+	rc = nvdimm_bus_check_dimm_count(acpi_desc->nvdimm_bus, dimm_count);
+	if (rc)
+		return rc;
+
+	/*
+	 * Now that dimms are successfully registered, and async registration
+	 * is flushed, attempt to enable event notification.
+	 */
+	list_for_each_entry(nfit_mem, &acpi_desc->dimms, list) {
+		struct kernfs_node *nfit_kernfs;
+
+		nvdimm = nfit_mem->nvdimm;
+		nfit_kernfs = sysfs_get_dirent(nvdimm_kobj(nvdimm)->sd, "nfit");
+		if (nfit_kernfs)
+			nfit_mem->flags_attr = sysfs_get_dirent(nfit_kernfs,
+					"flags");
+		sysfs_put(nfit_kernfs);
+		if (!nfit_mem->flags_attr)
+			dev_warn(acpi_desc->dev, "%s: notifications disabled\n",
+					nvdimm_name(nvdimm));
+	}
+
+	return devm_add_action_or_reset(acpi_desc->dev, shutdown_dimm_notify,
+			acpi_desc);
 }
 
 static void acpi_nfit_init_dsms(struct acpi_nfit_desc *acpi_desc)

drivers/acpi/nfit/nfit.h

@@ -82,6 +82,10 @@ enum nfit_root_notifiers {
 	NFIT_NOTIFY_UPDATE = 0x80,
 };
 
+enum nfit_dimm_notifiers {
+	NFIT_NOTIFY_DIMM_HEALTH = 0x81,
+};
+
 struct nfit_spa {
 	struct list_head list;
 	struct nd_region *nd_region;
@@ -128,6 +132,7 @@ struct nfit_mem {
 	struct acpi_nfit_system_address *spa_bdw;
 	struct acpi_nfit_interleave *idt_dcr;
 	struct acpi_nfit_interleave *idt_bdw;
+	struct kernfs_node *flags_attr;
 	struct nfit_flush *nfit_flush;
 	struct list_head list;
 	struct acpi_device *adev;

drivers/nvdimm/dimm_devs.c

@@ -263,6 +263,12 @@ const char *nvdimm_name(struct nvdimm *nvdimm)
 }
 EXPORT_SYMBOL_GPL(nvdimm_name);
 
+struct kobject *nvdimm_kobj(struct nvdimm *nvdimm)
+{
+	return &nvdimm->dev.kobj;
+}
+EXPORT_SYMBOL_GPL(nvdimm_kobj);
+
 unsigned long nvdimm_cmd_mask(struct nvdimm *nvdimm)
 {
 	return nvdimm->cmd_mask;

include/linux/libnvdimm.h

@@ -139,6 +139,7 @@ struct nd_blk_region *to_nd_blk_region(struct device *dev);
 struct nvdimm_bus_descriptor *to_nd_desc(struct nvdimm_bus *nvdimm_bus);
 struct device *to_nvdimm_bus_dev(struct nvdimm_bus *nvdimm_bus);
 const char *nvdimm_name(struct nvdimm *nvdimm);
+struct kobject *nvdimm_kobj(struct nvdimm *nvdimm);
 unsigned long nvdimm_cmd_mask(struct nvdimm *nvdimm);
 void *nvdimm_provider_data(struct nvdimm *nvdimm);
 struct nvdimm *nvdimm_create(struct nvdimm_bus *nvdimm_bus, void *provider_data,