powerpc/papr_scm: Add support for fetching nvdimm 'fuel-gauge' metric

We add support for reporting 'fuel-gauge' NVDIMM metric via
PAPR_PDSM_HEALTH pdsm payload. 'fuel-gauge' metric indicates the usage
life remaining of a papr-scm compatible NVDIMM. PHYP exposes this
metric via the H_SCM_PERFORMANCE_STATS.

The metric value is returned from the pdsm by extending the return
payload 'struct nd_papr_pdsm_health' without breaking the ABI. A new
field 'dimm_fuel_gauge' to hold the metric value is introduced at the
end of the payload struct and its presence is indicated by by
extension flag PDSM_DIMM_HEALTH_RUN_GAUGE_VALID.

The patch introduces a new function papr_pdsm_fuel_gauge() that is
called from papr_pdsm_health(). If fetching NVDIMM performance stats
is supported then 'papr_pdsm_fuel_gauge()' allocated an output buffer
large enough to hold the performance stat and passes it to
drc_pmem_query_stats() that issues the HCALL to PHYP. The return value
of the stat is then populated in the 'struct
nd_papr_pdsm_health.dimm_fuel_gauge' field with extension flag
'PDSM_DIMM_HEALTH_RUN_GAUGE_VALID' set in 'struct
nd_papr_pdsm_health.extension_flags'

Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200731064153.182203-3-vaibhav@linux.ibm.com

1 files changed, 49 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/pseries/papr_scm.c b/arch/powerpc/platforms/pseries/papr_scm.c
index f37f3f70007d..f439f0dfea7d 100644
--- a/arch/powerpc/platforms/pseries/papr_scm.c
+++ b/arch/powerpc/platforms/pseries/papr_scm.c
@@ -518,6 +518,51 @@ static int is_cmd_valid(struct nvdimm *nvdimm, unsigned int cmd, void *buf,
 	return 0;
 }
 
+static int papr_pdsm_fuel_gauge(struct papr_scm_priv *p,
+				union nd_pdsm_payload *payload)
+{
+	int rc, size;
+	u64 statval;
+	struct papr_scm_perf_stat *stat;
+	struct papr_scm_perf_stats *stats;
+
+	/* Silently fail if fetching performance metrics isn't  supported */
+	if (!p->stat_buffer_len)
+		return 0;
+
+	/* 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, "MemLife ", sizeof(stat->stat_id));
+	stat->stat_val = 0;
+
+	/* Fetch the fuel gauge and populate it in payload */
+	rc = drc_pmem_query_stats(p, stats, 1);
+	if (rc < 0) {
+		dev_dbg(&p->pdev->dev, "Err(%d) fetching fuel gauge\n", rc);
+		goto free_stats;
+	}
+
+	statval = be64_to_cpu(stat->stat_val);
+	dev_dbg(&p->pdev->dev,
+		"Fetched fuel-gauge %llu", statval);
+	payload->health.extension_flags |=
+		PDSM_DIMM_HEALTH_RUN_GAUGE_VALID;
+	payload->health.dimm_fuel_gauge = statval;
+
+	rc = sizeof(struct nd_papr_pdsm_health);
+
+free_stats:
+	kfree(stats);
+	return rc;
+}
+
 /* Fetch the DIMM health info and populate it in provided package. */
 static int papr_pdsm_health(struct papr_scm_priv *p,
 			    union nd_pdsm_payload *payload)
@@ -558,6 +603,10 @@ static int papr_pdsm_health(struct papr_scm_priv *p,
 
 	/* struct populated hence can release the mutex now */
 	mutex_unlock(&p->health_mutex);
+
+	/* Populate the fuel gauge meter in the payload */
+	papr_pdsm_fuel_gauge(p, payload);
+
 	rc = sizeof(struct nd_papr_pdsm_health);
 
 out: