On Tue, Jun 28, 2011 at 03:45:22PM -0700, Santosh Shilimkar wrote: > The udelay code doesn't use the per-cpu lpj variable. It uses the global > lpj. Secondly the calibration of no. of loops to be done is > precalculateed so overwrite shouldn't impact the scenario you mentioned. > > Though it has an issue where, pre-calculated loops can become short/long > based on new clock change which impacts both CPU's on OMAP, when the > other CPU is in in the middle of u-delay routine..
And there's also the issue where you can start a udelay loop on one CPU, be pre-empted and end up running it on a different CPU running at a different speed. The thing to bear in mind is that udelays are approximate at best - I did some investigation into the accuracy of the loops_per_jiffy calculation, and it _will_ produce shorter delays than expected by the fact that what is being calibrated is the udelay() loop _plus_ the timer interrupt overhead. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
