acpi/nfit: Issue Start ARS to retrieve existing records

ACPI 6.2 defines in section 9.20.7.2 that the OSPM may call a Start
ARS with Flags Bit [1] set upon receiving the 0x81 notification.

Upon receiving the notification, the OSPM may decide to issue
a Start ARS with Flags Bit [1] set to prepare for the retrieval
of existing records and issue the Query ARS Status function to
retrieve the records.

Add support to call a Start ARS from acpi_nfit_uc_error_notify()
with ND_ARS_RETURN_PREV_DATA set when HW_ERROR_SCRUB_ON is not set.

Link: http://www.uefi.org/sites/default/files/resources/ACPI_6_2.pdf
Signed-off-by: Toshi Kani <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Rafael J. Wysocki <[e-mail]>
Cc: Vishal Verma <[e-mail]>
Cc: Linda Knippers <[e-mail]>
Signed-off-by: Dan Williams <[e-mail]>

drivers/acpi/nfit/core.c

···
 	if (nd_desc) {
 		struct acpi_nfit_desc *acpi_desc = to_acpi_desc(nd_desc);
 
-		rc = acpi_nfit_ars_rescan(acpi_desc);
+		rc = acpi_nfit_ars_rescan(acpi_desc, 0);
 	}
 	device_unlock(dev);
 	if (rc)
···
 	memset(&ars_start, 0, sizeof(ars_start));
 	ars_start.address = spa->address;
 	ars_start.length = spa->length;
+	ars_start.flags = acpi_desc->ars_start_flags;
 	if (nfit_spa_type(spa) == NFIT_SPA_PM)
 		ars_start.type = ND_ARS_PERSISTENT;
 	else if (nfit_spa_type(spa) == NFIT_SPA_VOLATILE)
···
 	ars_start.address = ars_status->restart_address;
 	ars_start.length = ars_status->restart_length;
 	ars_start.type = ars_status->type;
+	ars_start.flags = acpi_desc->ars_start_flags;
 	rc = nd_desc->ndctl(nd_desc, NULL, ND_CMD_ARS_START, &ars_start,
 			sizeof(ars_start), &cmd_rc);
 	if (rc < 0)
···
 	list_for_each_entry(nfit_spa, &acpi_desc->spas, list)
 		acpi_nfit_async_scrub(acpi_desc, nfit_spa);
 	acpi_desc->scrub_count++;
+	acpi_desc->ars_start_flags = 0;
 	if (acpi_desc->scrub_count_state)
 		sysfs_notify_dirent(acpi_desc->scrub_count_state);
 	mutex_unlock(&acpi_desc->init_mutex);
···
 				return rc;
 		}
 
+	acpi_desc->ars_start_flags = 0;
 	if (!acpi_desc->cancel)
 		queue_work(nfit_wq, &acpi_desc->work);
 	return 0;
···
 	return 0;
 }
 
-int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc)
+int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc, u8 flags)
 {
 	struct device *dev = acpi_desc->dev;
 	struct nfit_spa *nfit_spa;
···
 
 		nfit_spa->ars_required = 1;
 	}
+	acpi_desc->ars_start_flags = flags;
 	queue_work(nfit_wq, &acpi_desc->work);
 	dev_dbg(dev, "%s: ars_scan triggered\n", __func__);
 	mutex_unlock(&acpi_desc->init_mutex);
···
 static void acpi_nfit_uc_error_notify(struct device *dev, acpi_handle handle)
 {
 	struct acpi_nfit_desc *acpi_desc = dev_get_drvdata(dev);
+	u8 flags = (acpi_desc->scrub_mode == HW_ERROR_SCRUB_ON) ?
+			0 : ND_ARS_RETURN_PREV_DATA;
 
-	acpi_nfit_ars_rescan(acpi_desc);
+	acpi_nfit_ars_rescan(acpi_desc, flags);
 }
 
 void __acpi_nfit_notify(struct device *dev, acpi_handle handle, u32 event)

drivers/acpi/nfit/mce.c

···
 			 * already in progress, just let that be the last
 			 * authoritative one
 			 */
-			acpi_nfit_ars_rescan(acpi_desc);
+			acpi_nfit_ars_rescan(acpi_desc, 0);
 		}
 		break;
 	}

drivers/acpi/nfit/nfit.h

···
 	struct list_head idts;
 	struct nvdimm_bus *nvdimm_bus;
 	struct device *dev;
+	u8 ars_start_flags;
 	struct nd_cmd_ars_status *ars_status;
 	size_t ars_status_size;
 	struct work_struct work;
···
 
 extern struct list_head acpi_descs;
 extern struct mutex acpi_desc_lock;
-int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc);
+int acpi_nfit_ars_rescan(struct acpi_nfit_desc *acpi_desc, u8 flags);
 
 #ifdef CONFIG_X86_MCE
 void nfit_mce_register(void);

include/uapi/linux/ndctl.h

···
 enum {
 	ND_ARS_VOLATILE = 1,
 	ND_ARS_PERSISTENT = 2,
+	ND_ARS_RETURN_PREV_DATA = 1 << 1,
 	ND_CONFIG_LOCKED = 1,
 };