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Kernel: Fix APIC timer calibration to be more accurate

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We were calibrating it to 260 instead of 250 ticks per second (being
off by one for the 1/10th second calibration time), resulting in
ticks of only ~3.6 ms instead of ~4ms. This gets us closer to ~4ms,
but because the APIC isn't nearly as precise as e.g. HPET, it will
only be a best effort. Then, use the higher precision reference
timer to more accurately calculate how many ticks we actually get
each second.

Also the frequency calculation was off, causing a "Frequency too slow"
error with VMware.

Fixes some problems observed in #5539
This commit is contained in:
Tom 2021-02-28 11:47:03 -07:00 • committed by Andreas Kling
parent f66adbdd95
commit cdbd878a14
7 changed files with 64 additions and 23 deletions
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3
Kernel/Time/HPETComparator.h
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@ -51,6 +51,9 @@ public:
virtual void set_periodic() override;
virtual void set_non_periodic() override;
virtual void disable() override;
virtual bool can_query_raw() const override { return true; }
virtual u64 current_raw() const override;
virtual u64 raw_to_ns(u64) const override;
virtual void reset_to_default_ticks_per_second() override;
virtual bool try_to_set_frequency(size_t frequency) override;