1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright 2014, Michael Ellerman, IBM Corp.
4 */
5
6 #include <stdbool.h>
7 #include <stdio.h>
8 #include <stdlib.h>
9
10 #include "ebb.h"
11
12
13 #define NUMBER_OF_EBBS 50
14
15 /*
16 * Test that if we overflow the counter while in the EBB handler, we take
17 * another EBB on exiting from the handler.
18 *
19 * We do this by counting with a stupidly low sample period, causing us to
20 * overflow the PMU while we're still in the EBB handler, leading to another
21 * EBB.
22 *
23 * We get out of what would otherwise be an infinite loop by leaving the
24 * counter frozen once we've taken enough EBBs.
25 */
26
ebb_callee(void)27 static void ebb_callee(void)
28 {
29 uint64_t siar, val;
30
31 val = mfspr(SPRN_BESCR);
32 if (!(val & BESCR_PMEO)) {
33 ebb_state.stats.spurious++;
34 goto out;
35 }
36
37 ebb_state.stats.ebb_count++;
38 trace_log_counter(ebb_state.trace, ebb_state.stats.ebb_count);
39
40 /* Resets the PMC */
41 count_pmc(1, sample_period);
42
43 out:
44 if (ebb_state.stats.ebb_count == NUMBER_OF_EBBS)
45 /* Reset but leave counters frozen */
46 reset_ebb_with_clear_mask(MMCR0_PMAO);
47 else
48 /* Unfreezes */
49 reset_ebb();
50
51 /* Do some stuff to chew some cycles and pop the counter */
52 siar = mfspr(SPRN_SIAR);
53 trace_log_reg(ebb_state.trace, SPRN_SIAR, siar);
54
55 val = mfspr(SPRN_PMC1);
56 trace_log_reg(ebb_state.trace, SPRN_PMC1, val);
57
58 val = mfspr(SPRN_MMCR0);
59 trace_log_reg(ebb_state.trace, SPRN_MMCR0, val);
60 }
61
back_to_back_ebbs(void)62 int back_to_back_ebbs(void)
63 {
64 struct event event;
65
66 SKIP_IF(!ebb_is_supported());
67
68 event_init_named(&event, 0x1001e, "cycles");
69 event_leader_ebb_init(&event);
70
71 event.attr.exclude_kernel = 1;
72 event.attr.exclude_hv = 1;
73 event.attr.exclude_idle = 1;
74
75 FAIL_IF(event_open(&event));
76
77 setup_ebb_handler(ebb_callee);
78
79 FAIL_IF(ebb_event_enable(&event));
80
81 sample_period = 5;
82
83 ebb_freeze_pmcs();
84 mtspr(SPRN_PMC1, pmc_sample_period(sample_period));
85 ebb_global_enable();
86 ebb_unfreeze_pmcs();
87
88 while (ebb_state.stats.ebb_count < NUMBER_OF_EBBS)
89 FAIL_IF(core_busy_loop());
90
91 ebb_global_disable();
92 ebb_freeze_pmcs();
93
94 count_pmc(1, sample_period);
95
96 dump_ebb_state();
97
98 event_close(&event);
99
100 FAIL_IF(ebb_state.stats.ebb_count != NUMBER_OF_EBBS);
101
102 return 0;
103 }
104
main(void)105 int main(void)
106 {
107 return test_harness(back_to_back_ebbs, "back_to_back_ebbs");
108 }
109
