Re: [Qemu-devel] [PATCH v2] hw/ptimer: Don't wrap around counter for expired timer that uses tick handler

[Dmitry Osipenko <digetx@gmail.com>]

On 25.06.2016 16:20, Mark Cave-Ayland wrote:
> On 25/06/16 13:35, Dmitry Osipenko wrote:
> 
>> Software should see timer counter wrap around only after IRQ being triggered.
>> Change returned counter value to "1" for the expired timer and avoid returning
>> wrapped around counter value in periodic mode for the timer that has bottom-half
>> handler setup, assuming it drives timer IRQ.
>>
>> This fixes regression introduced by the commit 5a50307 ("hw/ptimer: Perform
>> counter wrap around if timer already expired") on SPARC emulated machine as
>> reported by Mark Cave-Ayland.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>> ---
>>  hw/core/ptimer.c | 8 +++++---
>>  1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
>> index 05b0c27..8006442 100644
>> --- a/hw/core/ptimer.c
>> +++ b/hw/core/ptimer.c
>> @@ -93,10 +93,10 @@ uint64_t ptimer_get_count(ptimer_state *s)
>>          bool oneshot = (s->enabled == 2);
>>
>>          /* Figure out the current counter value.  */
>> -        if (s->period == 0 || (expired && (oneshot || use_icount))) {
>> +        if (expired && (oneshot || use_icount || s->bh != NULL)) {
>>              /* Prevent timer underflowing if it should already have
>>                 triggered.  */
>> -            counter = 0;
>> +            counter = 1;
>>          } else {
>>              uint64_t rem;
>>              uint64_t div;
>> @@ -143,7 +143,9 @@ uint64_t ptimer_get_count(ptimer_state *s)
>>
>>              if (expired && counter != 0) {
>>                  /* Wrap around periodic counter.  */
>> -                counter = s->limit - (counter - 1) % s->limit;
>> +                counter = s->delta = s->limit - (counter - 1) % s->limit;
>> +                /* Re-arm timer according to the wrapped around value.  */
>> +                ptimer_reload(s);
>>              }
>>          }
>>      } else {
>>
> 
> Hi Dmitry,
> 
> I ran through all of my OpenBIOS test images for qemu-system-sparc and AFAICT
> this fixes the issue without introducing any further regressions so:
> 
> Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> 
> 
> Many thanks,
> 
> Mark.
> 

Great! Thanks for testing it.

-- 
Dmitry