// SPDX-License-Identifier: GPL-2.0
#include <errno.h>
#include <inttypes.h>
#include <string.h>

#include <linux/compiler.h>
#include <linux/perf_event.h>
#include <linux/stddef.h>
#include <linux/types.h>

#include <asm/barrier.h>

#include "event.h"
#include "synthetic-events.h"
#include "debug.h"
#include "tsc.h"

u64 perf_time_to_tsc(u64 ns, struct perf_tsc_conversion *tc)
{
        u64 t, quot, rem;

        t = ns - tc->time_zero;
        quot = t / tc->time_mult;
        rem  = t % tc->time_mult;
        return (quot << tc->time_shift) +
               (rem << tc->time_shift) / tc->time_mult;
}

u64 tsc_to_perf_time(u64 cyc, struct perf_tsc_conversion *tc)
{
        u64 quot, rem;

        if (tc->cap_user_time_short)
                cyc = tc->time_cycles +
                        ((cyc - tc->time_cycles) & tc->time_mask);

        quot = cyc >> tc->time_shift;
        rem  = cyc & (((u64)1 << tc->time_shift) - 1);
        return tc->time_zero + quot * tc->time_mult +
               ((rem * tc->time_mult) >> tc->time_shift);
}

int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
                             struct perf_tsc_conversion *tc)
{
        u32 seq;
        int i = 0;

        while (1) {
                seq = pc->lock;
                rmb();
                tc->time_mult = pc->time_mult;
                tc->time_shift = pc->time_shift;
                tc->time_zero = pc->time_zero;
                tc->time_cycles = pc->time_cycles;
                tc->time_mask = pc->time_mask;
                tc->cap_user_time_zero = pc->cap_user_time_zero;
                tc->cap_user_time_short = pc->cap_user_time_short;
                rmb();
                if (pc->lock == seq && !(seq & 1))
                        break;
                if (++i > 10000) {
                        pr_debug("failed to get perf_event_mmap_page lock\n");
                        return -EINVAL;
                }
        }

        if (!tc->cap_user_time_zero)
                return -EOPNOTSUPP;

        return 0;
}

int perf_event__synth_time_conv(const struct perf_event_mmap_page *pc,
                                const struct perf_tool *tool,
                                perf_event__handler_t process,
                                struct machine *machine)
{
        union perf_event event = {
                .time_conv = {
                        .header = {
                                .type = PERF_RECORD_TIME_CONV,
                                .size = sizeof(struct perf_record_time_conv),
                        },
                },
        };
        struct perf_tsc_conversion tc;
        int err;

        if (!pc)
                return 0;
        err = perf_read_tsc_conversion(pc, &tc);
        if (err == -EOPNOTSUPP)
                return 0;
        if (err)
                return err;

        pr_debug2("Synthesizing TSC conversion information\n");

        event.time_conv.time_mult  = tc.time_mult;
        event.time_conv.time_shift = tc.time_shift;
        event.time_conv.time_zero  = tc.time_zero;
        event.time_conv.time_cycles = tc.time_cycles;
        event.time_conv.time_mask = tc.time_mask;
        event.time_conv.cap_user_time_zero = tc.cap_user_time_zero;
        event.time_conv.cap_user_time_short = tc.cap_user_time_short;

        return process(tool, &event, NULL, machine);
}

u64 __weak rdtsc(void)
{
        return 0;
}

size_t perf_event__fprintf_time_conv(union perf_event *event, FILE *fp)
{
        struct perf_record_time_conv *tc = (struct perf_record_time_conv *)event;
        size_t ret;

        ret  = fprintf(fp, "\n... Time Shift      %" PRI_lu64 "\n", tc->time_shift);
        ret += fprintf(fp, "... Time Multiplier %" PRI_lu64 "\n", tc->time_mult);
        ret += fprintf(fp, "... Time Zero       %" PRI_lu64 "\n", tc->time_zero);

        /*
         * The event TIME_CONV was extended for the fields from "time_cycles"
         * when supported cap_user_time_short, for backward compatibility,
         * prints the extended fields only if they are contained in the event.
         */
        if (event_contains(*tc, time_cycles)) {
                ret += fprintf(fp, "... Time Cycles     %" PRI_lu64 "\n",
                               tc->time_cycles);
                ret += fprintf(fp, "... Time Mask       %#" PRI_lx64 "\n",
                               tc->time_mask);
                ret += fprintf(fp, "... Cap Time Zero   %" PRId32 "\n",
                               tc->cap_user_time_zero);
                ret += fprintf(fp, "... Cap Time Short  %" PRId32 "\n",
                               tc->cap_user_time_short);
        }

        return ret;
}