perf pmu arm64: Fix reading the PMU cpu slots in sysfs

Commit f8ad601 ("perf pmu: Remove duplication around
EVENT_SOURCE_DEVICE_PATH") uses sysfs__read_ull() to read a full sysfs
path, which will never succeeds as it already comes with the sysfs mount
point in it, which sysfs__read_ull() will add again.

Fix it by reading the file using filename__read_ull(), that will not add
the sysfs mount point.

Fixes: f8ad601 ("perf pmu: Remove duplication around EVENT_SOURCE_DEVICE_PATH")
Signed-off-by: Haixin Yu <[email protected]>
Tested-by: Jing Zhang <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: James Clark <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: John Garry <[email protected]>
Cc: Leo Yan <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mike Leach <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: Haixin Yu

tools/perf/arch/arm64/util/pmu.c

@@ -54,10 +54,11 @@ double perf_pmu__cpu_slots_per_cycle(void)
 		perf_pmu__pathname_scnprintf(path, sizeof(path),
 					     pmu->name, "caps/slots");
 		/*
-		 * The value of slots is not greater than 32 bits, but sysfs__read_int
-		 * can't read value with 0x prefix, so use sysfs__read_ull instead.
+		 * The value of slots is not greater than 32 bits, but
+		 * filename__read_int can't read value with 0x prefix,
+		 * so use filename__read_ull instead.
 		 */
-		sysfs__read_ull(path, &slots);
+		filename__read_ull(path, &slots);
 	}
 
 	return slots ? (double)slots : NAN;