On 03/31/2014 07:44 PM, Ge Gao wrote:
Dear Jonathan, Thanks for answering my question. I am using Panda board(OMAP4430). It is using a 32K counter clock as the high resolution clock(arch/arm/plat-omap/couter_32k.c). But I also observe the same thing in Nexus 7 first generation(announced in 2012), which uses Nvidia Tegra 3 platform. I suspect the data that represents the time is cached, or it is using some older value in the interrupt case. It could be the Linux's time function problem. Is that possible? I actually tried using Jiffy, which is the built-in software clock. The time between each interrupt also varies big. My HZ setting is 1000. I also tried a later version of Linux, which is 3.7 or later. The result is the same. The implementation of the time function is very simple. Below is the function from 32K clock counter. It is reading the hardware clock, compute the difference between a static variable and update the time. For a different clock, only the "clocksource_32k.mult", "clocksource_32k.shift", would be different. Thanks.
You have to consider that there will be other things running with IRQs off, which will cause some jitter for your IRQ handler. This is nothing IIO specific.
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