acpi: nfit: Add support for detect platform CPU cache flush on power …

…loss

In ACPI 6.2a the platform capability structure has been added to the NFIT
tables. That provides software the ability to determine whether a system
supports the auto flushing of CPU caches on power loss. If the capability
is supported, we do not need to do dax_flush(). Plumbing the path to set the
property on per region from the NFIT tables.

This patch depends on the ACPI NFIT 6.2a platform capabilities support code
in include/acpi/actbl1.h.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

drivers/acpi/nfit/core.c

@@ -838,6 +838,18 @@ static bool add_flush(struct acpi_nfit_desc *acpi_desc,
 	return true;
 }
 
+static bool add_platform_cap(struct acpi_nfit_desc *acpi_desc,
+		struct acpi_nfit_capabilities *pcap)
+{
+	struct device *dev = acpi_desc->dev;
+	u32 mask;
+
+	mask = (1 << (pcap->highest_capability + 1)) - 1;
+	acpi_desc->platform_cap = pcap->capabilities & mask;
+	dev_dbg(dev, "%s: cap: %#x\n", __func__, acpi_desc->platform_cap);
+	return true;
+}
+
 static void *add_table(struct acpi_nfit_desc *acpi_desc,
 		struct nfit_table_prev *prev, void *table, const void *end)
 {
@@ -883,6 +895,10 @@ static void *add_table(struct acpi_nfit_desc *acpi_desc,
 	case ACPI_NFIT_TYPE_SMBIOS:
 		dev_dbg(dev, "%s: smbios\n", __func__);
 		break;
+	case ACPI_NFIT_TYPE_CAPABILITIES:
+		if (!add_platform_cap(acpi_desc, table))
+			return err;
+		break;
 	default:
 		dev_err(dev, "unknown table '%d' parsing nfit\n", hdr->type);
 		break;
@@ -2656,6 +2672,9 @@ static int acpi_nfit_register_region(struct acpi_nfit_desc *acpi_desc,
 	else
 		ndr_desc->numa_node = NUMA_NO_NODE;
 
+	if(acpi_desc->platform_cap & ACPI_NFIT_CAPABILITY_CACHE_FLUSH)
+		set_bit(ND_REGION_PERSIST_CACHE, &ndr_desc->flags);
+
 	list_for_each_entry(nfit_memdev, &acpi_desc->memdevs, list) {
 		struct acpi_nfit_memory_map *memdev = nfit_memdev->memdev;
 		struct nd_mapping_desc *mapping;
@@ -3464,6 +3483,7 @@ static __init int nfit_init(void)
 	BUILD_BUG_ON(sizeof(struct acpi_nfit_smbios) != 9);
 	BUILD_BUG_ON(sizeof(struct acpi_nfit_control_region) != 80);
 	BUILD_BUG_ON(sizeof(struct acpi_nfit_data_region) != 40);
+	BUILD_BUG_ON(sizeof(struct acpi_nfit_capabilities) != 16);
 
 	guid_parse(UUID_VOLATILE_MEMORY, &nfit_uuid[NFIT_SPA_VOLATILE]);
 	guid_parse(UUID_PERSISTENT_MEMORY, &nfit_uuid[NFIT_SPA_PM]);

drivers/acpi/nfit/nfit.h

@@ -202,6 +202,7 @@ struct acpi_nfit_desc {
 	unsigned long dimm_cmd_force_en;
 	unsigned long bus_cmd_force_en;
 	unsigned long bus_nfit_cmd_force_en;
+	unsigned int platform_cap;
 	int (*blk_do_io)(struct nd_blk_region *ndbr, resource_size_t dpa,
 			void *iobuf, u64 len, int rw);
 };

drivers/nvdimm/pmem.c

@@ -35,6 +35,7 @@
 #include "pmem.h"
 #include "pfn.h"
 #include "nd.h"
+#include "nd-core.h"
 
 static struct device *to_dev(struct pmem_device *pmem)
 {
@@ -334,7 +335,8 @@ static int pmem_attach_disk(struct device *dev,
 		dev_warn(dev, "unable to guarantee persistence of writes\n");
 		fua = 0;
 	}
-	wbc = nvdimm_has_cache(nd_region);
+	wbc = nvdimm_has_cache(nd_region) &&
+		!test_bit(ND_REGION_PERSIST_CACHE, &nd_region->flags);
 
 	if (!devm_request_mem_region(dev, res->start, resource_size(res),
 				dev_name(&ndns->dev))) {

include/linux/libnvdimm.h

@@ -47,6 +47,11 @@ enum {
 
 	/* region flag indicating to direct-map persistent memory by default */
 	ND_REGION_PAGEMAP = 0,
+	/*
+	 * Platform ensures entire CPU store data path is flushed to pmem on
+	 * system power loss.
+	 */
+	ND_REGION_PERSIST_CACHE = 1,
 
 	/* mark newly adjusted resources as requiring a label update */
 	DPA_RESOURCE_ADJUSTED = 1 << 0,