On Tue, May 31, 2011 at 2:53 PM, Reinhard Meyer u-boot@emk-elektronik.de wrote:
Dear Simon Glass,
On Mon, May 30, 2011 at 5:24 PM, Graeme Russgraeme.russ@gmail.com wrote:
Hi Reinhard,
On Tue, May 31, 2011 at 4:57 AM, Reinhard Meyer
...
make_timeout() can be arch/soc/platform specific and take into account to return at least such a value that the timeout is never cut short. (In case of a 10 ms NIOS timer, make_timeout(5) would have to return the value 20, resulting in a real timeout of at least 10 ms but upto 20 ms )
What about this:
u32 start = get_timer();
while (!timer_expired(start, timeout)) ...
Hi Graham,
I like this, although I have a small preference for:
u32 stop = time_get_future_ms(1234);
while (!time_reached(stop)) ..
I would perfectly like such a solution, it is equivalent to what I have been proposing almost a year ago!
Don't forget the API will have a get_current_ms() so we can do duration measurements. So you could still accidentally do:
u32 stop = get_current_ms() + 1234;
bypassing the resolution correction. If time_reached() did the resolution correction, would this solve the problem of API misuse (yes, I know it puts a complicated calculation back in the loop)
since it possibly means the processing happens up front. However any such function is good and I hope you can add it to your API.
Exactly! And (saying it silently) this would not mandate that the now hidden internal timer needs to be in ms units, it could be the bare "natural" tick of the hardware... Making time_get_future() to return the "tick" (in whatever granularity) that has to be passed would reduce time_reached() to a very simple function.
Half the point of refreshing the timer API was to solidify the fact that timers operate on a fixed time base (milliseconds or microseconds) so they can be used trivially for a variety of things (delays, timeouts, durations measurement etc). Ticks can be very short, so doing durations would require 64-bit 'start tick', and a conversion at the end:
u64 start = get_current_tick(); ... do something ... u32 duration = ticks_to_ms(get_current_tick() - start);
Yetch! - We will not be exposing ticks!
But I get the feeling that exactly this simplicity of above concept is the problem for people that have the urge to invent elaborate and complicated solutions ;)
I like simple as much as the next guy - I also like hard to misuse ;)
Regards,
Graeme