Re: [Qemu-devel] [PATCH] Don't enable a HPET timer if HPET is disabled

[Alex Bligh]

Paolo,

On 22 Feb 2014, at 10:55, Paolo Bonzini wrote:

> Il 22/02/2014 10:03, Alex Bligh ha scritto:
>> I am unfamiliar with the HPET code but symmetry suggests perhaps the 'else'
>> condition should be changed too:
>> 
>>            } else if (deactivating_bit(old_val, new_val, HPET_TN_ENABLE) ||
>>                       !hpet_enabled(s)) {
>>                      hpet_del_timer(timer);
>>            }
>> 
>> -- 
> 
> I thought the same, but there is no need for that.  When the enabled bit goes
> from set to clear, all timers are disabled:
> 
>            } else if (deactivating_bit(old_val, new_val, HPET_CFG_ENABLE)) {
>                /* Halt main counter and disable interrupt generation. */
>                s->hpet_counter = hpet_get_ticks(s);
>                for (i = 0; i < s->num_timers; i++) {
>                    hpet_del_timer(&s->timer[i]);
>                }
>            }
> 
> So hpet_del_timer would be a nop if !hpet_enabled(s).

Thanks. I didn't know whether HPET_CFG_ENABLE and HPET_TN_ENABLE were 
equivalent.

-- 
Alex Bligh