[U-Boot] [PATCH V5 1/3] arm: Add support for MB86R0x SoCs

[Wolfgang Denk]

Dear =?ISO-8859-1?Q?Matthias_Wei=DFer?=,

In message <4C5FA669.6070303 at arcor.de> you wrote:
> 
> >> +	tmo = usec_to_tick(usec);
> >> +	tmp = get_ticks() + tmo;	/* get current timestamp */
> >> +
> >> +	while (get_ticks()<  tmp)	/* loop till event */
> >> +		 /*NOP*/;
> >
> > This is broken when the timer wraps around. Compare the limit against
> > the difference, to make use of unsigned arithmetics.
> 
> Isn't this a theoretical problem? The timer increments with approx. 
> 160kHz. get_ticks() returns a 64 bit value which wraps all ~ 3*10^6 
> years. I don't expect my hardware to work that long without a reboot.

Such assumptions that problems might remain theoretical have cuased
enough real problems already. I mean, if it was difficult to write
correct code I might turn a blind eye, but why not fix it? It's a
trivial change...

> Can you point me to an example where the timer stuff is done right? I 
> see it done differently on nearly all ARM SOCs.

Rule of a thumb: to copy from ARM means copying problems.

Use:
	while ((get_ticks() - tmp) < tmo)
		;

Best regards,

Wolfgang Denk

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