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 >> - 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) >> - 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.
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 _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
