nfit: add support for NVDIMM "latch" flag

Add support in the NFIT BLK I/O path for the "latch" flag
defined in the "Get Block NVDIMM Flags" _DSM function:

http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf

This flag requires the driver to read back the command register after it
is written in the block I/O path.  This ensures that the hardware has
fully processed the new command and moved the aperture appropriately.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/acpi/nfit.c b/drivers/acpi/nfit.c
index 11aa513f2fda6325f22331e07365a6d330ef719b..628a42c41ab126d12997ab02fd805df6af698c98 100644 (file)
--- a/drivers/acpi/nfit.c
+++ b/drivers/acpi/nfit.c
@@ -1059,7 +1059,9 @@ static void write_blk_ctl(struct nfit_blk *nfit_blk, unsigned int bw,
 
        writeq(cmd, mmio->base + offset);
        wmb_blk(nfit_blk);
-       /* FIXME: conditionally perform read-back if mandated by firmware */
+
+       if (nfit_blk->dimm_flags & ND_BLK_DCR_LATCH)
+               readq(mmio->base + offset);
 }
 
 static int acpi_nfit_blk_single_io(struct nfit_blk *nfit_blk,
@@ -1266,6 +1268,28 @@ static int nfit_blk_init_interleave(struct nfit_blk_mmio *mmio,
        return 0;
 }
 
+static int acpi_nfit_blk_get_flags(struct nvdimm_bus_descriptor *nd_desc,
+               struct nvdimm *nvdimm, struct nfit_blk *nfit_blk)
+{
+       struct nd_cmd_dimm_flags flags;
+       int rc;
+
+       memset(&flags, 0, sizeof(flags));
+       rc = nd_desc->ndctl(nd_desc, nvdimm, ND_CMD_DIMM_FLAGS, &flags,
+                       sizeof(flags));
+
+       if (rc >= 0 && flags.status == 0)
+               nfit_blk->dimm_flags = flags.flags;
+       else if (rc == -ENOTTY) {
+               /* fall back to a conservative default */
+               nfit_blk->dimm_flags = ND_BLK_DCR_LATCH;
+               rc = 0;
+       } else
+               rc = -ENXIO;
+
+       return rc;
+}
+
 static int acpi_nfit_blk_region_enable(struct nvdimm_bus *nvdimm_bus,
                struct device *dev)
 {
@@ -1340,6 +1364,13 @@ static int acpi_nfit_blk_region_enable(struct nvdimm_bus *nvdimm_bus,
                return rc;
        }
 
+       rc = acpi_nfit_blk_get_flags(nd_desc, nvdimm, nfit_blk);
+       if (rc < 0) {
+               dev_dbg(dev, "%s: %s failed get DIMM flags\n",
+                               __func__, nvdimm_name(nvdimm));
+               return rc;
+       }
+
        nfit_flush = nfit_mem->nfit_flush;
        if (nfit_flush && nfit_flush->flush->hint_count != 0) {
                nfit_blk->nvdimm_flush = devm_ioremap_nocache(dev,

diff --git a/drivers/acpi/nfit.h b/drivers/acpi/nfit.h
index 815cb561cdba19992726d5a3cc3349499f5f0f67..79b6d83875c1de1aed4bc67e091a4d2e3aa88204 100644 (file)
--- a/drivers/acpi/nfit.h
+++ b/drivers/acpi/nfit.h
@@ -40,6 +40,10 @@ enum nfit_uuids {
        NFIT_UUID_MAX,
 };
 
+enum {
+       ND_BLK_DCR_LATCH = 2,
+};
+
 struct nfit_spa {
        struct acpi_nfit_system_address *spa;
        struct list_head list;
@@ -131,6 +135,7 @@ struct nfit_blk {
        u64 stat_offset;
        u64 cmd_offset;
        void __iomem *nvdimm_flush;
+       u32 dimm_flags;
 };
 
 enum spa_map_type {