On Thu, Sep 22, 2022 at 2:45 PM Philippe Mathieu-Daudé <
f4bug@amsat.org> wrote:
On 22/9/22 17:58, Tyler Ng wrote:
> 1. Adds fields to hold the value of mtime in timer_upper0 and timer_lower0.
>
> 2. Changes the read and write functions to use the mtime fields.
>
> 3. Updates the value of mtime in update_mtime() by extrapolating the
> time elapsed. This will need to change if/when the prescalar is
> implemented.
>
> 4. Adds a qtest for the ibex timer.
>
> Signed-off-by: Tyler Ng <tkng@rivosinc.com>
> ---
> hw/timer/ibex_timer.c | 98 +++++++++++++------
> include/hw/timer/ibex_timer.h | 6 ++
> tests/qtest/ibex-timer-test.c | 178 ++++++++++++++++++++++++++++++++++
> tests/qtest/meson.build | 3 +-
> 4 files changed, 256 insertions(+), 29 deletions(-)
> create mode 100644 tests/qtest/ibex-timer-test.c
> -static void ibex_timer_update_irqs(IbexTimerState *s)
> +/*
> + * The goal of this function is to:
> + * 1. Check if the timer is enabled. If not, return false,
> + * 2. Calculate the amount of time that has passed since.
> + * 3. Extrapolate the number of ticks that have passed, and add it to `mtime`.
> + * 4. Return true.
> + */
> +static bool update_mtime(IbexTimerState *s)
> {
> - uint64_t value = s->timer_compare_lower0 |
> - ((uint64_t)s->timer_compare_upper0 << 32);
> - uint64_t next, diff;
> - uint64_t now = cpu_riscv_read_rtc(s->timebase_freq);
> -
> if (!(s->timer_ctrl & R_CTRL_ACTIVE_MASK)) {
> - /* Timer isn't active */
> + return false;
> + }
> + /* Get the time then extrapolate the number of ticks that have elapsed */
> + uint64_t mtime = get_mtime(s);
> + int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> + int64_t elapsed = now - s->timer_last_update;
> + if (elapsed < 0) {
> + /* We jumped back in time. */
> + mtime -= muldiv64((uint64_t)(-elapsed), s->timebase_freq,
> + NANOSECONDS_PER_SECOND);
> + } else {
> + mtime += muldiv64(elapsed, s->timebase_freq, NANOSECONDS_PER_SECOND);
> + }
> + s->timer_lower0 = mtime & 0xffffffff;
> + s->timer_upper0 = (mtime >> 32) & 0xffffffff;
Could use extract64(mtime, 0, 32) and extract64(mtime, 32, 32);
Didn't know about this function, thanks.
> + /* update last-checkpoint timestamp */
> + s->timer_last_update = now;
> + return true;
> +}