Hi Wolfgang,
On 30/05/11 22:31, Wolfgang Denk wrote:
Dear Graeme Russ,
In message 4DE383D3.7020008@gmail.com you wrote:
Some platforms are _way_ worse than this - I am sure I have seen a udelay() done with the millisecond time - So udelay(100) could be closer to udelay(1000) - So your above 5 second delay could take as long as 50 seconds!!!
That should show up quickly as soon as you run a "sleep 5" command on the console (which is implemented like that).
while (test_for_event() == 0) { now = get_timer(0); if ((now - start) > timeout) handle_timeout();
udelay(100);}
Here the loop overhead caused by short delay which may result in a high number of calls to test_for_event() gets eliminated because the time reference is independet of the delay.
I personally think _any_ timeout greater than 1s (maybe even >500ms) should be done this way
Agreed. As soon as the timeout is >> the interval size of the underlying timer service this is the best we can do.
start = get_timer(0);
do_something_complicated();
now = get_timer(0);
printf("execution time: %ld millisec\n", now - start);
Currently fails spectacularly if do_something_complicated() involves a delay loop which calls reset_timer()
Note that I (intentionally) always used argument 0 in the calls to get_timer(). I think we really should get rid of this argument.
Agreed - I am more than willing to update all existing timer usages to a completely new set of timer API functions. I think suffering the pain of moving to a more well defined API would be better than trying to clunk around the existing one.
I think we all fairly well agree on how U-Boot will maintain a millisecond (and possibly microsecond) timer in a platform independent manner using a platform defined tick counter. Defining a timer API around that is simply a matter of taste - particularly when it comes to dealing with precision issues. I think your delta function is a good start - However maybe something more like ms_delta(u32 from, u32 to) would be a more appropriate name as it clears the way for us_delta()
Regards,
Graeme