Thanks Greg. Perfect, a pointer in the right direction helps a lot. Just one quick followup; In your opinion, given the 60Mhz clock on our M5272 CPU, does the interrupt latency sound in the right ballpark to you?
Thanks, Harry On Nov 21, 2007 4:04 PM, Greg Ungerer <[EMAIL PROTECTED]> wrote: > Hi Harry, > > Harry Gunnarsson wrote: > > Hi everybody, > > I am running uClinux on a custom board with the following configuration > > - 20070131 distro with 2.6.22.6 <http://2.6.22.6> kernel > > - M5272 CPU clocked at 60MHz (not 66..) > > - Compiled with CodeSourcery 4.2-47 > > - Custom board has serial port, RJ45 ethernet > > > > Essentially, our application only has one real-time requirement, > > everything else is more of a control nature where there is no real time > > constraints. The real-time event is served with an interrupt as > > - Interrupt line hooked up to ext 3 > > - priority 5 > > - request_irq called with SA_INTERRUPT > > > > We did some profiling on this interrupt and with a extremely stripped > > down driver for the interrupt we see the following numbers > > - 12.5 microsecond latency from interrupt line is pulled until service > > routine is getting called. > > > > If my arithmetic skills serve me right, that's 750 clock cycles. > > > > Questions: > > - Does this sound slow? Is this the latency you'd expect from a system > > above? > > - Does anyone else have any other interrupt performance stats for > > ColdFire that he/she wants to share? > > - Is there any way one can speed up the handling of an interrupt without > > re-inventing linux? > > One approach is to directly handle interrupts in your driver code, > and bypass the standard Linux interrupt handling entry/exit code. > But you do need to be very careful with what you do in your "fast" > interrupt handler. > > As an example of how this might work look at the 5249 audio > driver in the linux-2.4.x/drivers/char/m5249audio.c. It bypasses > the linux interrupt handling, and uses its own assembler version > of an interrupt routine (specifically to get low latency). > > Regards > Greg > > > ------------------------------------------------------------------------ > Greg Ungerer -- Chief Software Dude EMAIL: [EMAIL PROTECTED] > Secure Computing Corporation PHONE: +61 7 3435 2888 > 825 Stanley St, FAX: +61 7 3891 3630 > Woolloongabba, QLD, 4102, Australia WEB: http://www.SnapGear.com > _______________________________________________ > uClinux-dev mailing list > [email protected] > http://mailman.uclinux.org/mailman/listinfo/uclinux-dev > This message was resent by [email protected] > To unsubscribe see: > http://mailman.uclinux.org/mailman/options/uclinux-dev > _______________________________________________ uClinux-dev mailing list [email protected] http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by [email protected] To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev
