powerpc/papr_scm: Fetch nvdimm health information from PHYP

Implement support for fetching nvdimm health information via
H_SCM_HEALTH hcall as documented in Ref[1]. The hcall returns a pair
of 64-bit bitmap, bitwise-and of which is then stored in
'struct papr_scm_priv' and subsequently partially exposed to
user-space via newly introduced dimm specific attribute
'papr/flags'. Since the hcall is costly, the health information is
cached and only re-queried, 60s after the previous successful hcall.

The patch also adds a  documentation text describing flags reported by
the the new sysfs attribute 'papr/flags' is also introduced at
Documentation/ABI/testing/sysfs-bus-papr-pmem.

[1] commit 58b278f568f0 ("powerpc: Provide initial documentation for
PAPR hcalls")

Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20200615124407.32596-4-vaibhav@linux.ibm.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-papr-pmem b/Documentation/ABI/testing/sysfs-bus-papr-pmem
new file mode 100644
index 000000000000..5b10d036a8d4
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-papr-pmem
@@ -0,0 +1,27 @@
+What:		/sys/bus/nd/devices/nmemX/papr/flags
+Date:		Apr, 2020
+KernelVersion:	v5.8
+Contact:	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>, linux-nvdimm@lists.01.org,
+Description:
+		(RO) Report flags indicating various states of a
+		papr-pmem NVDIMM device. Each flag maps to a one or
+		more bits set in the dimm-health-bitmap retrieved in
+		response to H_SCM_HEALTH hcall. The details of the bit
+		flags returned in response to this hcall is available
+		at 'Documentation/powerpc/papr_hcalls.rst' . Below are
+		the flags reported in this sysfs file:
+
+		* "not_armed"	: Indicates that NVDIMM contents will not
+				  survive a power cycle.
+		* "flush_fail"	: Indicates that NVDIMM contents
+				  couldn't be flushed during last
+				  shut-down event.
+		* "restore_fail": Indicates that NVDIMM contents
+				  couldn't be restored during NVDIMM
+				  initialization.
+		* "encrypted"	: NVDIMM contents are encrypted.
+		* "smart_notify": There is health event for the NVDIMM.
+		* "scrubbed"	: Indicating that contents of the
+				  NVDIMM have been scrubbed.
+		* "locked"	: Indicating that NVDIMM contents cant
+				  be modified until next power cycle.