On 08/04/2013 11:28 PM, Lambrecht Jürgen wrote: > On 08/02/2013 10:33 AM, Michael Schnell wrote: > [snip] >> - how to assign certain interrupts to that core and have ISRs run >> there only dedicatedly interrupting the "main loop" and not ever being >> blocked by any Linux activity ? >> here I found this: >> https://access.redhat.com/site/solutions/15482 >> In fact of course the hardware defines if/how a certain Interrupt can be >> assigned to a certain CPU. How is this usually done when using ARM >> Cortex A9+ cores ?. > The ARM A9 datasheet will say what registers to write to assign IRQs to > CPU1, and make Linux not to use those IRQs. > Then the max. latency is determined by the clock speed and CPU cycles > the bare metal program needs to react (should be in datasheet). I asked a Freescale FAE and the cortex A9 is AMP capable (I also needed to know this for my project): "Actually, you can check on ARM community web site, where you will see that the CortexA9/GIC infrastructure enables AMP implementation. http://forums.arm.com/index.php?/topic/15656-cortex-a9-amp/ The Global Interrupt Controller gives you the possibility to assign specific IT to specific cores. But a CortexA9 is not very RT oriented (for that ARM has created the Cortex R Family, with improved RT execution time)." > > About the non-determinism of modern hardware: if a chip is AMP capable > the heating up of 1 core should not influence the other core. I believe > heat spreads vertically (to the heatsink) and not so much horizontally. > So an RTOS should run with a stable frequency. (anyhow, Linux should not > touch the other CPU, or need to touch it). That Freescale FAE warns about the voltage scaling: "you have only one power line to supply all the cores, so all processor would be impacted. There is no way to change that." So indeed a problem with modern hardware.. Kind regards, Jürgen-- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
