On Fri, May 27, 2011 at 3:28 AM, Wolfgang Denk wd@denx.de wrote:
Dear Simon Glass,
In message BANLkTikWwuymrJtMEHBZkvNgNBK1e=RdWA@mail.gmail.com you wrote:
Can we have a microsecond one also please? Some sort of microsecond
I guess you cannot, at least not in general. In worst case that would mean we have to process 1e6 interrupts per second, which leaves little time for anything useful.
If we implemented a sync_us_timer(), we could either:
a) Never kick it using an interrupt at all (only kick it in udelay()) b) Kick it in a much slower interrupt (1ms+ period)
Remember, the kicking of the sync function does not need to correlate to the incrementing of the tick counter - Only to the roll-over period of the tick counter.
For a 64-bit sub microsecond tick counter, interrupts will probably not ever be needed (unless the tick frequency is ludicrous - even a nanosecond tick counter will take 213 days to wrap) so in this case, sync_us_timer() would be fine
Regards,
Graeme