kernel/tools/testing/selftests/powerpc/pmu/ebb/back_to_back_ebbs_test.c

   1 /*
   2  * Copyright 2014, Michael Ellerman, IBM Corp.
   3  * Licensed under GPLv2.
   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
  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
  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
 105 int main(void)
 106 {
 107         return test_harness(back_to_back_ebbs, "back_to_back_ebbs");
 108 }