[RFC][PATCH 2/2] powerpc/papr_scm: Implement support for reporting generic nvdimm stats

[Vaibhav Jain <vaibhav@linux.ibm.com>]

Add support for reporting papr-scm supported generic nvdimm stats by
implementing support for handling ND_CMD_GET_STAT in
'papr_scm_ndctl().

The mapping between libnvdimm generic nvdimm-stats and papr-scm
specific performance-stats is embedded inside 'dimm_stats_map[]'. This
array is queried by newly introduced 'papr_scm_get_stat()' that
verifies if the requested nvdimm-stat is supported and if yes does an
hcall via 'drc_pmem_query_stat()' to request the performance-stat and
return it back to libnvdimm.

Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
---
 arch/powerpc/platforms/pseries/papr_scm.c | 66 ++++++++++++++++++++++-
 1 file changed, 65 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index 835163f54244..51eeab3376fd 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -25,7 +25,8 @@
 	((1ul << ND_CMD_GET_CONFIG_SIZE) | \
 	 (1ul << ND_CMD_GET_CONFIG_DATA) | \
 	 (1ul << ND_CMD_SET_CONFIG_DATA) | \
-	 (1ul << ND_CMD_CALL))
+	 (1ul << ND_CMD_CALL) |		   \
+	 (1ul << ND_CMD_GET_STAT))
 
 /* DIMM health bitmap bitmap indicators */
 /* SCM device is unable to persist memory contents */
@@ -120,6 +121,16 @@ struct papr_scm_priv {
 static LIST_HEAD(papr_nd_regions);
 static DEFINE_MUTEX(papr_ndr_lock);
 
+/* Map generic nvdimm stats to papr-scm stats */
+static const char * const dimm_stat_map[] = {
+	[ND_DIMM_STAT_INVALID] = NULL,
+	[ND_DIMM_STAT_MEDIA_READS] = "MedRCnt ",
+	[ND_DIMM_STAT_MEDIA_WRITES] = "MedWCnt ",
+	[ND_DIMM_STAT_READ_REQUESTS] = "HostLCnt",
+	[ND_DIMM_STAT_WRITE_REQUESTS] = "HostSCnt",
+	[ND_DIMM_STAT_MAX] = NULL,
+};
+
 static int drc_pmem_bind(struct papr_scm_priv *p)
 {
 	unsigned long ret[PLPAR_HCALL_BUFSIZE];
@@ -728,6 +739,54 @@ static int papr_scm_service_pdsm(struct papr_scm_priv *p,
 	return pdsm_pkg->cmd_status;
 }
 
+/*
+ * For a given pdsm request call an appropriate service function.
+ * Returns errors if any while handling the pdsm command package.
+ */
+static int papr_scm_get_stat(struct papr_scm_priv *p,
+			     struct nd_cmd_get_dimm_stat *dimm_stat)
+
+{
+	int rc;
+	ssize_t size;
+	struct papr_scm_perf_stat *stat;
+	struct papr_scm_perf_stats *stats;
+
+	/* Check if the requested stat-id is supported */
+	if (dimm_stat->stat_id >= ARRAY_SIZE(dimm_stat_map) ||
+	    !dimm_stat_map[dimm_stat->stat_id]) {
+		dev_dbg(&p->pdev->dev, "Invalid stat-id %lld\n", dimm_stat->stat_id);
+		return -ENOSPC;
+	}
+
+	/* Allocate request buffer enough to hold single performance stat */
+	size = sizeof(struct papr_scm_perf_stats) +
+		sizeof(struct papr_scm_perf_stat);
+
+	stats = kzalloc(size, GFP_KERNEL);
+	if (!stats)
+		return -ENOMEM;
+
+	stat = &stats->scm_statistic[0];
+	memcpy(&stat->stat_id, dimm_stat_map[dimm_stat->stat_id],
+	       sizeof(stat->stat_id));
+	stat->stat_val = 0;
+
+	/* Fetch the statistic from PHYP and copy it to provided payload */
+	rc = drc_pmem_query_stats(p, stats, 1);
+	if (rc < 0) {
+		dev_dbg(&p->pdev->dev, "Err(%d) fetching stat '%.8s'\n",
+			rc, stat->stat_id);
+		kfree(stats);
+		return rc;
+	}
+
+	dimm_stat->int_val = be64_to_cpu(stat->stat_val);
+
+	kfree(stats);
+	return 0;
+}
+
 static int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc,
 			  struct nvdimm *nvdimm, unsigned int cmd, void *buf,
 			  unsigned int buf_len, int *cmd_rc)
@@ -772,6 +831,11 @@ static int papr_scm_ndctl(struct nvdimm_bus_descriptor *nd_desc,
 		*cmd_rc = papr_scm_service_pdsm(p, call_pkg);
 		break;
 
+	case ND_CMD_GET_STAT:
+		*cmd_rc = papr_scm_get_stat(p,
+					    (struct nd_cmd_get_dimm_stat *)buf);
+		break;
+
 	default:
 		dev_dbg(&p->pdev->dev, "Unknown command = %d\n", cmd);
 		return -EINVAL;
-- 
2.28.0