[Xen-devel] About pit irq

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

Currently pit irq is enabled when using pit as clocksource or 
taking pit as broadcast means for deep C-state. I'm curious
whether pit irq is really required for the 1st case. When pit
is chosen as clocksource, 10ms periodical pit interrupt converts
16 counter into monotonic 32bit stamp, and then ~27ms platform 
overflow timer converts 32bit into 64bit stamp. Is the first
conversion really necessary? platform overflow timer is chosen
as 1/2 period, and it looks safe enough to convert from 16bit
into 64bit stamp directly. Just one special bit to indicate
whether counter counts down or up.

Thanks,
Kevin
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