powerpc/papr_scm: Fix build failure when

The following build failure occurs when CONFIG_PERF_EVENTS is not set
as generic pmu functions are not visible in that scenario.

arch/powerpc/platforms/pseries/papr_scm.c:372:35: error: ‘struct perf_event’ has no member named ‘attr’
         p->nvdimm_events_map[event->attr.config],
                                   ^~
In file included from ./include/linux/list.h:5,
                 from ./include/linux/kobject.h:19,
                 from ./include/linux/of.h:17,
                 from arch/powerpc/platforms/pseries/papr_scm.c:5:
arch/powerpc/platforms/pseries/papr_scm.c: In function ‘papr_scm_pmu_event_init’:
arch/powerpc/platforms/pseries/papr_scm.c:389:49: error: ‘struct perf_event’ has no member named ‘pmu’
  struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
                                                 ^~
./include/linux/container_of.h:18:26: note: in definition of macro ‘container_of’
  void *__mptr = (void *)(ptr);     \
                          ^~~
arch/powerpc/platforms/pseries/papr_scm.c:389:30: note: in expansion of macro ‘to_nvdimm_pmu’
  struct nvdimm_pmu *nd_pmu = to_nvdimm_pmu(event->pmu);
                              ^~~~~~~~~~~~~
In file included from ./include/linux/bits.h:22,
                 from ./include/linux/bitops.h:6,
                 from ./include/linux/of.h:15,
                 from arch/powerpc/platforms/pseries/papr_scm.c:5:

Fix the build issue by adding check for CONFIG_PERF_EVENTS config option
and also add stub function for papr_scm_pmu_register to handle
the CONFIG_PERF_EVENTS=n case. Also move the position of macro
"to_nvdimm_pmu" inorder to merge it in CONFIG_PERF_EVENTS=y block.

based on libnvdimm-for-next tree)

Fixes: 4c08d4b ("powerpc/papr_scm: Add perf interface support") (Commit id
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Link: https://lore.kernel.org/r/20220323164550.109768-2-kjain@linux.ibm.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Author: kjain101

arch/powerpc/platforms/pseries/papr_scm.c

@@ -69,8 +69,6 @@
 #define PAPR_SCM_PERF_STATS_EYECATCHER __stringify(SCMSTATS)
 #define PAPR_SCM_PERF_STATS_VERSION 0x1
 
-#define to_nvdimm_pmu(_pmu)	container_of(_pmu, struct nvdimm_pmu, pmu)
-
 /* Struct holding a single performance metric */
 struct papr_scm_perf_stat {
 	u8 stat_id[8];
@@ -346,6 +344,9 @@ static ssize_t drc_pmem_query_stats(struct papr_scm_priv *p,
 	return 0;
 }
 
+#ifdef CONFIG_PERF_EVENTS
+#define to_nvdimm_pmu(_pmu)	container_of(_pmu, struct nvdimm_pmu, pmu)
+
 static int papr_scm_pmu_get_value(struct perf_event *event, struct device *dev, u64 *count)
 {
 	struct papr_scm_perf_stat *stat;
@@ -558,6 +559,10 @@ static void papr_scm_pmu_register(struct papr_scm_priv *p)
 	dev_info(&p->pdev->dev, "nvdimm pmu didn't register rc=%d\n", rc);
 }
 
+#else
+static void papr_scm_pmu_register(struct papr_scm_priv *p) { }
+#endif
+
 /*
  * Issue hcall to retrieve dimm health info and populate papr_scm_priv with the
  * health information.