Re: Programming Local apic timer

["Peter Teoh" <htmldeveloper@xxxxxxxxx>]

just saw this from QEMU (vl.c) - on how its uses the HPET and RTC
timer (just a a brief extracts), and this is a userspace program,
assuming that the kernel has been compiled for it (CONFIG_HPET,
CONFIG_HPET_TIMER etc):

static int hpet_start_timer(struct qemu_alarm_timer *t)
{
    struct hpet_info info;
    int r, fd;

    fd = open("/dev/hpet", O_RDONLY);
    if (fd < 0)
        return -1;

    /* Set frequency */
    r = ioctl(fd, HPET_IRQFREQ, RTC_FREQ);
    if (r < 0) {
        fprintf(stderr, "Could not configure '/dev/hpet' to have a
1024Hz timer. This is not a fatal\n"
                "error, but for better emulation accuracy type:\n"
                "'echo 1024 > /proc/sys/dev/hpet/max-user-freq' as root.\n");
        goto fail;
    }

    /* Check capabilities */
    r = ioctl(fd, HPET_INFO, &info);
    if (r < 0)
        goto fail;

    /* Enable periodic mode */
    r = ioctl(fd, HPET_EPI, 0);
    if (info.hi_flags && (r < 0))
        goto fail;

    /* Enable interrupt */
    r = ioctl(fd, HPET_IE_ON, 0);
    if (r < 0)
        goto fail;

    enable_sigio_timer(fd);
    t->priv = (void *)(long)fd;

    return 0;
fail:
    close(fd);
    return -1;
}

static void hpet_stop_timer(struct qemu_alarm_timer *t)
{
    int fd = (long)t->priv;

    close(fd);
}

static int rtc_start_timer(struct qemu_alarm_timer *t)
{
    int rtc_fd;

    TFR(rtc_fd = open("/dev/rtc", O_RDONLY));
    if (rtc_fd < 0)
        return -1;
    if (ioctl(rtc_fd, RTC_IRQP_SET, RTC_FREQ) < 0) {
        fprintf(stderr, "Could not configure '/dev/rtc' to have a 1024
Hz timer. This is not a fatal\n"
                "error, but for better emulation accuracy either use a
2.6 host Linux kernel or\n"
                "type 'echo 1024 > /proc/sys/dev/rtc/max-user-freq' as
root.\n");
        goto fail;
    }
    if (ioctl(rtc_fd, RTC_PIE_ON, 0) < 0) {
    fail:
        close(rtc_fd);
        return -1;
    }

    enable_sigio_timer(rtc_fd);

    t->priv = (void *)(long)rtc_fd;

    return 0;
}

static void rtc_stop_timer(struct qemu_alarm_timer *t)
{
    int rtc_fd = (long)t->priv;

    close(rtc_fd);
}

Have fun!!!!
-- 
Regards,
Peter Teoh

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