On 23/05/11 16:29, Albert ARIBAUD wrote: > Hi all, > > Sorry, could not follow the discussion although I find it very > interesting, so I will handle the task of coming in late and asking the > silly questions. > > Le 23/05/2011 07:25, Graeme Russ a écrit : > >> On Mon, May 23, 2011 at 3:02 PM, J. William Campbell >> <jwilliamcampb...@comcast.net> wrote: >>> On 5/22/2011 6:42 PM, Graeme Russ wrote: >>>> >>>> OK, so in summary, we can (in theory) have: >>>> - A timer API in /lib/ with a single u32 get_timer(u32 base) function >>>> - A HAL with two functions >>>> - u32 get_raw_ticks() >>>> - u32 get_raw_tick_rate() which returns the tick rate in kHz (which >>>> max's out at just after 4GHz) >>>> - A helper function in /lib/ u32 get_raw_ms() which uses get_raw_ticks() >>>> and get_tick_rate() to correctly maintain the ms counter used by >>>> get_timer() - This function can be weak (so next point) >>>> - If the hardware supports a native 32-bit ms counter, get_raw_ms() >>>> can be overridden to simply return the hardware counter. In this case, >>>> get_raw_ticks() would return 1 > > Are you sure you did not mean 'get_raw_ticks_rate' here? Besides, I'd
Yes, I did mean get_raw_ticks_rate() > like the name to specify the units used: 'get_raw_ticks_rate_in_khz' (or > conversively 'get_raw_ticks_per_ms', depending on which is simpler to > implement and use). > indeed, get_raw_ticks_per_ms() is a better name >>>> - Calling of get_raw_ticks() regularly in the main loop (how ofter will >>>> depend on the raw tick rate, but I image it will never be necessary >>>> to call more often than once every few minutes) > > That's to keep track of get_raw_ticks() rollovers, right? And then the Yes > get_timer function (which, again, I would prefer to have '... in ms' > expressed in its name) would call get_raw_ticks() in confidence that at > most one rollover may have occurred since the last time the helper > function was called, so a simple difference of the current vs last tick > value will always be correct. Correct - And a change to get_ms_timer() could be in order if generally supported, but this would be a big patch across a lot of code for a simple rename >>>> - If the hardware implements a native 32-bit 1ms counter, no call in >>>> the main loop is required >>>> - An optional HAL function u32 get_raw_us() which can be used for >>>> performance profiling (must wrap correctly) >>> >>> Hi All, >>> Graeme, I think you have stated exactly what is the "best" approach to >>> this problem. I will provide a version of "get_raw_ms" that is initialized >>> using get_raw_tick_rate that will work for all "reasonable" values of >>> raw_tick_rate. This will be the "generic" solution. Both the initialization >>> function and the get_raw_ms function can be overridden if there is reason to >>> do so, like "exact" clock rates. I will do the same with get_raw_us. This >>> will be posted sometime on Monday for people to review, and to make sure I >>> didn't get too far off base. Thank you to both Graeme and Reinhard for >>> looking at/working on this.. Hopefully, this solution will put this timing >>> issue to rest for all future ports as well as the presently existing ones. > > In Greame's description, I did not see a get_raw_ms, only a get_raw_us. > Was this last one a typo or is that a third HAL function? get_raw_ms() is used by get_timer(). get_raw_us() is an optional function which can be used for performance profiling >> Great - I am in the middle of cleaning up the current usages of the timer >> API, reducing it all down to get_timer() - I will then 'libify' >> get_timer() and setup the hooks into the HAL get_raw_ticks() and >> get_raw_tick_rate() API >> >> I think there will need to be a lot of cleanup, especially in arch/arm to >> get this to all fit >> >> Regards, >> >> Graeme > > Amicalement, Regards, Graeme _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
