On Mon, Apr 7, 2008 at 2:35 PM, Neil Armstrong <[EMAIL PROTECTED]> wrote: > Hi, > First of all, I'm quite new to linux real-time. > I'm trying to port the I-pipe patch for my company's arm926ejs based > Soc, i successfully run the 2.6.24 kernel with the I-pipe 1.9-01 patch > for arm. > > While running the testsuite on the platform I have some negative values > (for latency for example), so I'm not sure of my patch.
Small negative latencies may be normal, but something like -110 us is completely abnormal. There is definitely something wrong with your implementation. > > I based my work on the integrator patch for a decrementer timer. The > timer available is a 16bit decrementer with a 256 ticks prescaler with > the ARM clock running at 144Mhz. (decrementer's initial value for 1ms is > 5636 ticks). > > I joined the full output and the board specific I-pipe functions. > Gilles Chanteperdrix told me it would be better to use an one-shot timer > instead of the autoreload feature What I meant is that the autoreload feature is dangerous when the timer is used in one-shot mode: if the programmed shot is short, you have a risk of spurious timer interrupt. It the programmed shot is very short, you have a risk to hog the box completely. , but the kernel stops right after > adeos takes control of the timer ! What do you mean ? Adeos alwyas has control of the timer. You know when Xenomai takes control of the timer when the variale __ipipe_mach_timer_stolen is non zero. So, what you should do is program the timer in periodic mode (using autoreload feature if you want, if you do not want, you will have to program next shot in the timer interrupt code) as long as __ipipe_mach_timer_stolen is 0, and stop using the autoreload feature when __ipipe_mach_timer_stolen is 1 (or when ipipe_mach_set_dec is called). > > I read it could be useful to benchmark the Scheduling latency, but where > do I find the correct value ? The correct value is the maximum value returned by the latency test. But, there is probably a problem with your implementation, so the figures are irrelevant. -- Gilles _______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
