Re: [Qemu-devel] [PATCH v2] arm_mptimer: Fix timer shutdown

[Peter Maydell]

On 2 July 2015 at 18:20, Dmitry Osipenko <address@hidden> 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 timer if enable bit isn't set.
>
> Signed-off-by: Dmitry Osipenko <address@hidden>
> ---
>
> v2: Avoid calling timer_del() if the timer was already disabled as per
>     Peter Maydell suggestion.
>
>  hw/timer/arm_mptimer.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/hw/timer/arm_mptimer.c b/hw/timer/arm_mptimer.c
> index 8b93b3c..51c18de 100644
> --- a/hw/timer/arm_mptimer.c
> +++ b/hw/timer/arm_mptimer.c
> @@ -122,11 +122,17 @@ static void timerblock_write(void *opaque, hwaddr addr,
>      case 8: /* Control.  */
>          old = tb->control;
>          tb->control = value;
> -        if (((old & 1) == 0) && (value & 1)) {
> +        if (((old & 1) == 0) && ((value & 1) == 0)) {
> +            break;
> +        }
> +        if (value & 1) {
>              if (tb->count == 0 && (tb->control & 2)) {
>                  tb->count = tb->load;
>              }
>              timerblock_reload(tb, 1);
> +        } else {
> +            /* Shutdown timer.  */
> +            timer_del(tb->timer);


This will now cause us to do the "reload the timer"
logic if you write a 1 to the control bit when it was
already 1, which we didn't do before.

The logic I suggested in my previous review
comment gets this right...

-- PMM