selftests/powerpc/pmu: Add selftest to check constraint for number of counters in use.

Testcase for group constraint check for number of counters in use. The
number of programmable counters is from PMC1 to PMC4. Testcase uses four
events with PMC1 to PMC4 and 5th event without any PMC which is expected
to fail since it is exceeding the number of counters in use.
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220610134113.62991-19-atrajeev@linux.vnet.ibm.com

tools/testing/selftests/powerpc/pmu/event_code_tests/Makefile

 # SPDX-License-Identifier: GPL-2.0
 CFLAGS += -m64
 
-TEST_GEN_PROGS := group_constraint_pmc56_test group_pmc56_exclude_constraints_test
+TEST_GEN_PROGS := group_constraint_pmc56_test group_pmc56_exclude_constraints_test group_constraint_pmc_count_test
 
 top_srcdir = ../../../../../..
 include ../../../lib.mk

tools/testing/selftests/powerpc/pmu/event_code_tests/group_constraint_pmc_count_test.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2022, Athira Rajeev, IBM Corp.
+ */
+
+#include <stdio.h>
+#include "../event.h"
+#include "../sampling_tests/misc.h"
+
+/*
+ * Testcase for number of counters in use.
+ * The number of programmable counters is from
+ * performance monitor counter 1 to performance
+ * monitor counter 4 (PMC1-PMC4). If number of
+ * counters in use exceeds the limit, next event
+ * should fail to schedule.
+ */
+
+static int group_constraint_pmc_count(void)
+{
+	struct event *e, events[5];
+	int i;
+
+	/* Check for platform support for the test */
+	SKIP_IF(platform_check_for_tests());
+
+	/*
+	 * Test for number of counters in use.
+	 * Use PMC1 to PMC4 for leader and 3 sibling
+	 * events. Trying to open fourth event should
+	 * fail here.
+	 */
+	e = &events[0];
+	event_init(e, 0x1001a);
+
+	e = &events[1];
+	event_init(e, 0x200fc);
+
+	e = &events[2];
+	event_init(e, 0x30080);
+
+	e = &events[3];
+	event_init(e, 0x40054);
+
+	e = &events[4];
+	event_init(e, 0x0002c);
+
+	FAIL_IF(event_open(&events[0]));
+
+	/*
+	 * The event_open will fail on event 4 if constraint
+	 * check fails
+	 */
+	for (i = 1; i < 5; i++) {
+		if (i == 4)
+			FAIL_IF(!event_open_with_group(&events[i], events[0].fd));
+		else
+			FAIL_IF(event_open_with_group(&events[i], events[0].fd));
+	}
+
+	for (i = 1; i < 4; i++)
+		event_close(&events[i]);
+
+	return 0;
+}
+
+int main(void)
+{
+	return test_harness(group_constraint_pmc_count, "group_constraint_pmc_count");
+}