1/*
2 * Copyright 2018, Data61
3 * Commonwealth Scientific and Industrial Research Organisation (CSIRO)
4 * ABN 41 687 119 230.
5 *
6 * This software may be distributed and modified according to the terms of
7 * the BSD 2-Clause license. Note that NO WARRANTY is provided.
8 * See "LICENSE_BSD2.txt" for details.
9 *
10 * @TAG(DATA61_BSD)
11 */
12#pragma once
13
14#include <stdint.h>
15#include <string.h>
16#include <simple/simple.h>
17#include <utils/frequency.h>
18
19// uses the simple extended bootinfo interface to attempt to determine the tsc frequency
20// returns 0 on failure
21static inline uint32_t
22x86_get_tsc_freq_from_simple(simple_t *simple) {
23    // the simple interface is a bit awkward and doesn't give us a way to just get the last 4
24    // bytes so we have to define some scratch space to get what we want. use a char array instead
25    // of a custom struct so we're not worrying about padding and aliasing etc
26    char buf[sizeof(seL4_BootInfoHeader) + 4];
27    ssize_t ret = simple_get_extended_bootinfo(simple, SEL4_BOOTINFO_HEADER_X86_TSC_FREQ, buf, sizeof(buf));
28    if (ret == sizeof(buf)) {
29        uint32_t freq;
30        memcpy(&freq, buf + sizeof(seL4_BootInfoHeader), 4);
31        // convert mhz to hz
32        return freq * MHZ;
33    }
34    return 0;
35}
36