On Sun, 29 Nov 2015, Geert Uytterhoeven wrote:
This still heavily depends on the processing time spent in
NCR5380_read(). You should never use a value derived from
loops_per_jiffy for a non-empty loop,
Sure but the time-out condition isn't supposed to be precise.
Plus/minus a jiffy is no problem. Plus/minus a second is no good.
as it may take much longer. Always compare with an maximum end time
instead.
That can't work with interrupts disabled, which was the problem I was
trying to solve by use of loops_per_jiffy.
NCR5380_poll_politely() in mainline doesn't work with interrupts disabled
either, hence patch 21.
E.g.:
end = jiffies + 2; /* 1 jiffie + 1 safeguard */
do {
if ((NCR5380_read(reg1) & bit1) == val1)
return 0;
cpu_relax();
} while (time_before(jiffies, end);
And a similar loop for "Busy-wait for up to 20 ms".
Interrupts may be disabled during that loop also. Please refer to (and/or
respond to) patch 21, "ncr5380: Sleep when polling, if possible", in which
these changes were made.
--
Gr{oetje,eeting}s,
Geert
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