LXR linux/tools/testing/selftests/powerpc/pmu/ebb/back_to_back_ebbs

   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
  27static 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
  43out:
  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
  62int 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        dump_ebb_state();
  95
  96        event_close(&event);
  97
  98        FAIL_IF(ebb_state.stats.ebb_count != NUMBER_OF_EBBS);
  99
 100        return 0;
 101}
 102
 103int main(void)
 104{
 105        return test_harness(back_to_back_ebbs, "back_to_back_ebbs");
 106}
 107