[U-Boot] U-Boot Timer Qualification

[Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>]

On 19:47 Tue 28 Apr     , Wolfgang Denk wrote:
> Dear Ladislav Michl,
> 
> In message <20090428151147.GA19683@linux-mips.org> you wrote:
> > 
> > a lot of changes are entering arm tree, many without any commit message.
> > And now we have some special cases which needs some special care for yet
> > unclear reason. OMAP3 timer precission was discussed to death and patch
> > still didn't went in, because it needs to be verified against some
> > document you are claiming is not mandatory.
> 
> Just in case there is any doubt here:
> 
> There is no, and I say *no*, mandatory verification of any timing
> precision in U-Boot.
> 
> We all agree that precision is a good thing to have, it it must come
> at a reasonable effort, and there is no reason to drive it into
> extreme precision.
Personnaly I never ask extreme precision
I ask to known the precision

as the timer is incorrect to known where we go is important

> 
> Clock signals may need an accuracy of 1 or 2% or better - as we may
> see character corruption if the baudrate generators are off too far -
> but this is usually a hardware issue in the first place.
> 
> System timers (like udelay() etc.) in U-Boot do not need such a level
> of accuracy. That does not mean we should intentionally be inaccurate.
> 
> And of course actual testing is good, and documentation of the test
> results is even better.
> 
> But: it is not mandatory. Not in U-Boot (and also not in Linux, to the
> best of my knowledge).
As example when the timer was send by a dev at first and he will send a fix
I think it's start to be mandatory to ask him to test it an a the real hard
It will avoid to have a new fix again and again
which will mean that the timer is never been check in a real use case

> 
> See my previuous posting. I don;t think that a generic test method
> that works on all boards would be possible.
but a docmument and code to do is good and will hepl the dev evenif we can
known and support all boards. This will be improve with patch.

Best Regards,
J.