powerpc/perf: Fix PMU constraint check for EBB events

The power PMU group constraints includes check for EBB events to make
sure all events in a group must agree on EBB. This will prevent
scheduling EBB and non-EBB events together. But in the existing check,
settings for constraint mask and value is interchanged. Patch fixes the
same.

Before the patch, PMU selftest "cpu_event_pinned_vs_ebb_test" fails with
below in dmesg logs. This happens because EBB event gets enabled along
with a non-EBB cpu event.

  [35600.453346] cpu_event_pinne[41326]: illegal instruction (4)
  at 10004a18 nip 10004a18 lr 100049f8 code 1 in
  cpu_event_pinned_vs_ebb_test[10000000+10000]

Test results after the patch:

  $ ./pmu/ebb/cpu_event_pinned_vs_ebb_test
  test: cpu_event_pinned_vs_ebb
  tags: git_version:v5.12-rc5-93-gf28c3125acd3-dirty
  Binding to cpu 8
  EBB Handler is at 0x100050c8
  read error on event 0x7fffe6bd4040!
  PM_RUN_INST_CMPL: result 9872 running/enabled 37930432
  success: cpu_event_pinned_vs_ebb

This bug was hidden by other logic until commit 1908dc91 (perf:
Tweak perf_event_attr::exclusive semantics).

Fixes: 4df48999 ("powerpc/perf: Add power8 EBB support")
Reported-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
[mpe: Mention commit 1908dc91]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1617725761-1464-1-git-send-email-atrajeev@linux.vnet.ibm.com

arch/powerpc/perf/isa207-common.c

@@ -447,8 +447,8 @@ int isa207_get_constraint(u64 event, unsigned long *maskp, unsigned long *valp,
 	 * EBB events are pinned & exclusive, so this should never actually
 	 * hit, but we leave it as a fallback in case.
 	 */
-	mask  |= CNST_EBB_VAL(ebb);
-	value |= CNST_EBB_MASK;
+	mask  |= CNST_EBB_MASK;
+	value |= CNST_EBB_VAL(ebb);
 
 	*maskp = mask;
 	*valp = value;