[Qemu-devel] Re: Fix ptimer_get_count overflow.

[Vladimir Prus]

Vladimir Prus wrote:

> 
> At present, ptimers have a slight inaccuracy that can lead to
> overflow. The period is stored as 64.32 fixed point number.
> ptimer_reload uses both integer and fractional part of the perion
> when computing when the next event should happen. ptimer_get_count,
> however, uses only integer part of the period. Therefore, when
> ptimer_get_count is called very soon after ptimer_reload the value
> returned may be greater than the value ptimer_reload has set.
> And if the counter was 0xFFFFFFFF, this may result in overflow.
> 
> This was observed in SH4A emulation as "time jumps", where system
> time gets magically increased by 10 minutes sometimes.
> 
> This patch fixes this. The math is not the most accurate possible,
> but it's relatively fast and fixes the problems.

Ping?

- Volodya

primer_overflow.diff
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