Messages in this thread | | | Date | Sun, 29 Nov 2015 21:25:53 +1100 (AEDT) | From | Finn Thain <> | Subject | Re: [PATCH 22/71] ncr5380: Eliminate selecting state |
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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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