Hi all, I'd like to kindly ask for some help with my embedded system. I'm using the Vortex86DX SoC (it's a x86 32 clone) on my PC104 board. I've managed to apply and run the 2.6.33.7.2-rt30 RT linux. It supports the full preemption (PREEMPT_RT enabled). I've run the cyclictest (preemption tests) and then I've realized, that the HIGH_RESOLUTION_TIMER is not supported on this SoC (yet... I hope :-) ). Moreove the low-res counter resolution is 1ms (as shown at cat /proc/timer_list), which is unacceptable for my application. I've searched deeper in the specification of this SoC and I've found, that the Vortex86DX supports two i8254 timers. One is used for DMA, interrupt controller and disk, but the second seems to be free :-). root@lukma:~# cat /proc/ioports 0000-001f : dma1 0020-0021 : pic1 0040-0043 : timer0 0050-0053 : timer1 -> for use? In the i8254 specification it is written, that it is possible to feed the counter with 10MHz, which would be sufficient. I've poked around in the 2.6.33.7.2-rt30 source code and I've found, that mostly the COMEDI "staged driver" supports this chip. It looks that this driver has some issues and should not be used (it looks rather old). I have got following questions: 1. It seems, that i8254/53 is in some kind standard timer chip (like 8237 - DMA chip) and should already HAVE driver (for x86 i386, i486, i586). 2. It should be possible to use it as a source for HIGH RESOLUTION TIMER to provide 1/10 MHz = 100 ns resolution. (for me 1us is enough). I suppose, that "only" proper callbacks should be provided for HIGH_RESOLUTION_TIMER framework. 3. It should be a common problem for x86 arch clones (in the embedded world) to provide one or other source for HIGH RESOLUTION TIMERS to achieve proper schedule timing. How this problem is tackled on the other x86 variants? There MUST be either Local Advanced Programmable Interrupt Controller (Local APIC) or High Precision Event Timer. The vortex86DX SoC has 800MHz clock freq, so 1us timer precision shall be achievable. What is the clock source for High Resolution Timers on other processors with up to i586 ISA? 4. I'd be glad to have an opportunity to solve this problem (I mean to write a driver for i8254) but I don't want to reinvent the wheel :-) Any help/ideas/hints are very welcome. I've got some experience with ARM/PXA cores, so x86 SoC is somewhat new for my real-time, embedded adventure. Thanks in advance and regards, Åukasz Majewski -- To unsubscribe from this list: send the line "unsubscribe linux-8086" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
