Hello. Paul Mackerras wrote:
What problem do you see arising from this?
Timers firing too early.
Only if the minimum interrupt latency is less than 1 decrementer tick. That seems pretty unlikely to me unless you have a very slow timebase frequency.
Well, MPC8540 has 825 MHz CPU clock yet decrementor/timebase are clocked with 25 MHz clock if I don't mistake. That gives us 33 CPU clocks of available interrupt latency...
In fact what we should program the decrementer to is:
timeout - (is_booke? 0: 1) - min_interrupt_latency
BTW, why not handle the decrementer difference right in set_dec() where we already have #ifdef'ed code?
I was assuming that min_interrupt_latency (measured in timebase ticks) would be at least 1, but apparently some systems can have a timebase frequency as low as 1kHz, so we'll have to have an ifdef or something.
IMHO it's better to have #ifdef based on the decremeter model and forget about the whole issue, rather than to #ifdef based on some bizarre system with slowish decremeter, isn't it?
Paul.
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