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Date: Sat, 22 Feb 2014 11:55:25 +0100
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Subject: Re: [Qemu-devel] [PATCH] Don't enable a HPET timer if HPET is
	disabled
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To: Alex Bligh <alex@alex.org.uk>, Matt Lupfer <mlupfer@ddn.com>
Cc: QEMU Developers <qemu-devel@nongnu.org>

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).

Paolo