On Sun, Jul 5, 2015 at 8:39 AM, Dmitry Osipenko <dig...@gmail.com> wrote:
> Timer, running in periodic mode, can't be stopped or coming one-shot
> tick won't be canceled because timer control code just doesn't handle
> timer disabling. Fix it by deleting the timer if enable bit isn't set.
>
> Timer won't start periodic ticking if ONE-SHOT -> PERIODIC mode change
> happened after one-shot tick was completed. Fix it by starting ticking
> only if the timer isn't ticking right now.
>
> To avoid code churning, these two fixes are squashed in one commit.
>
> Signed-off-by: Dmitry Osipenko <dig...@gmail.com>
> ---
>
> Commits are squashed as per Peter Crosthwaite suggestion.
>
> hw/timer/arm_mptimer.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/hw/timer/arm_mptimer.c b/hw/timer/arm_mptimer.c
> index 8b93b3c..0e132b1 100644
> --- a/hw/timer/arm_mptimer.c
> +++ b/hw/timer/arm_mptimer.c
> @@ -122,11 +122,18 @@ static void timerblock_write(void *opaque, hwaddr addr,
> case 8: /* Control. */
> old = tb->control;
> tb->control = value;
> - if (((old & 1) == 0) && (value & 1)) {
> - if (tb->count == 0 && (tb->control & 2)) {
> + if (value & 1) {
> + if ((old & 1) && (tb->count != 0)) {
> + /* Do nothing if timer is ticking right now. */
> + break;
> + }
> + if (tb->control & 2) {
So when the timer was previously disabled (!(old & 1)) and the count
is non-zero this will cause a spurious auto-reload. I don't this
causes a bug today because the code as-is doesn't support arbitrary
count values, but it is a developer trap should the assumption that
tb->count equals either 0 or the reload value not hold true.
> tb->count = tb->load;
> }
> timerblock_reload(tb, 1);
> + } else if (old & 1) {
> + /* Shutdown the timer. */
> + timer_del(tb->timer);
In general, this seems to now dup the code paths for control and
load/counter writes. Both now have a del and reload call for various
changes-of state. I had a go to see if I can consolidate. Turns out,
doing so should implement timer pause and resumption while fixing both
of your bugs, I'll send some patches.
Regards,
Peter
> }
> break;
> case 12: /* Interrupt status. */
> --
> 2.4.4
>
>
