Dear Graeme Russ, > On closer inspection, some do, some don't. All ARMv7 (OMAP, S5P, Tegra2) > do. at91 is odd - It looks like it uses interrupts, but get_timer() and > udelay() both end up calling get_timer_raw() (with udelay only having > millisecond resolution it seems). Some others can be configured to > increment the timer using an interrupt. ARM is, quite frankly, a complete > mess - It has a mass of *_timer_masked() functions which the core timer > functions are 'wafer thin' wrapper around, udelay() silently resets > the timebase trashing get_timer() loops etc.
Please look at current master for at91. http://git.denx.de/?p=u-boot.git;a=blob;f=arch/arm/cpu/arm926ejs/at91/timer.c;h=a0876879d3907af553d832bea187a062a22b9bd4;hb=5d1ee00b1fe1180503f6dfc10e87a6c6e74778f3 AT91 uses a 32 bit hardware register that by means of a prescaler is made to increment at a rate in the low megahertz range. This results in a wrap approximately every 1000 seconds. Actually this would be sufficient for all known uses of udelay() and get_timer() timeout loops. However, this hardware register is extended to 64 bits by software every time it is read (by detecting rollovers). Since a wrap of that 64 bit "tick" would occur after the earth has ended, it is simple to obtain milliseconds from it by doing a 64 bit division. Best Regards, Reinhard _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
