Dear Reinhard Meyer,
In message <4cc62b6c.30...@emk-elektronik.de> you wrote:
>
> In such cases I prefer to use:
>
> uint64_t etime;
> ...
> etime = get_ticks() + get_tbclk(); /* 1 second */
> do {
> whatever;
> udelay (xx);
> } while (condition && get_ticks() <= etime);
>
> That is far more accurate than calling udelay() 100000 times.
It may be more accuratre, but it may also be HORRIBLY WRONG!!
Do NOT do that!! NEVER implement such a delay loop as
end = time() + delay;
while (time() < end)
...
It fails in case the timer wraps around.
Assume 32 bit counters, start time = 0xFFFFFFF0, delay = 0x20. It
will compute end = 0x10, the while codition is immediately false, and
you don't have any delay at all, which most probably generates a
false error condition.
Correct implementation of a timeout like that should always look like
that:
start = time();
while ((time() - start) < delay)
...
This works much better (assuming unsigned arithmetics).
Best regards,
Wolfgang Denk
--
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de
Ein weiser Herrscher kann in einem großen Land mehr Gutes bewirken
als in einem kleinen - ein dummer Herrscher aber auch viel mehr Un-
fug. Da weise Herrscher seltener sind als dumme, war ich schon immer
gegen große Reiche skeptisch. - Herbert Rosendorfer
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