[U-Boot] [RFC] ARM timing code refactoring

[Wolfgang Denk <wd@denx.de>]

Dear Reinhard Meyer,

In message <4D3C0271.4070306@emk-elektronik.de> you wrote:
>
> There were several suggestions about that in the past (including from me)
> that involve rework everywhere HZ related timeouts are used. I still
> prefer a method as follows (because it does not need repeated mul/div calculations
> nor necessarily 64 bit arithmetic):
> 
> u32 timeout = timeout_init(100); /* 100ms timeout */
> 
> do {...} while (!timed_out(timeout));

I dislike this approach. I immediately fear the same problem I just
saw (incorrectly) in Albert's proposal - timeout_init() seems to
store the timeouut information in some internal varoable, which is
then checked by timed_out() - this is bound to fail as soon as
somebody atttempts to nest timeouts.

Your implementation may be different, but you can bet sooner or later
comes up with such a bugy implementation.

And it is not needed.

PLease see my proposal: we do not needs several timer or timeout
related functions, all we need is a plain "get timer" function,
without any arguments.  And the resulting code makes it obvious to the
reader that such loops can be nested as you like.

> time_out(x):
>    return ((i32)(x - fast_tick)) < 0;
> 
> If the tick were really high speed (and then 64 bits),
> fast_tick could be derived by shifting the tick some bits to the right.

I have no idea what "fast_tick" versus "tick" means here, nor why we
would need more than one tick.

Best regards,

Wolfgang Denk

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