powerpc/perf: Implement get_cpu_str()

powerpc/perf: Implement get_cpu_str()

With a file ~/.cache/pmu-events/004d0100-core.json describing Power8 PMU events we would need to run:

	perf stat \
		--events-file ~/.cache/pmu-events/004d0100-core.json \
		-e PM_CYC sleep 1

With this get_cpu_str(), On Powerpc, we can skip the --events-file option and run:

perf stat -e PM_CYC sleep 1

---
Changelog[v3]:
[Tobias Klauser]: Fix some changelog damage to patch.

Changelog[v2]:
[Michael Ellerman]: Use PVR instead of AUXV variables

 tools/perf/arch/powerpc/util/header.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

index 6c1b8a7..306bf35 100644
@@ -6,6 +6,7 @@
 
 #include "../../util/header.h"
 #include "../../util/util.h"
+#include "../../util/jevents.h"
 
 #define mfspr(rn)       ({unsigned long rval; \
 			 asm volatile("mfspr %0," __stringify(rn) \

@@ -32,3 +33,14 @@ get_cpuid(char *buffer, size_t sz)
 	}
 	return -1;
 }
+
+char *
+get_cpu_str(void)
+{
+	char *bufp;
+
+	if (asprintf(&bufp, "%.8lx-core", mfspr(SPRN_PVR)) < 0)
+		bufp = NULL;
+
+	return bufp;
+}

1.8.3.1

cheers