On 12/01/2010 12:14 PM, Russell King - ARM Linux wrote: > On Wed, Dec 01, 2010 at 11:36:10AM -0500, Stephen Caudle wrote: >> On 11/30/2010 01:07 PM, Russell King - ARM Linux wrote: >>> Sorry, missed this. >>> >>> If it's a private peripheral, it can only be accessed from its associated >>> CPU. What that means is you don't want to enable the interrupt on other >>> CPUs as the peripheral may not be present or initialized on that CPU. >> >> Understood. But the alternative is to require all code that requests a >> PPI to have to enable the IRQ on the other cores. This seems >> unreasonable to me. > > It is also unreasonable to have one core enabling the PPI on other > cores where the hardware behind the interrupt may not have been > initialized yet. If it is a private interrupt for a private peripheral, > then only the associated CPU should be enabling that interrupt. > > I guess this is something which genirq can't cope with, in which case > either genirq needs to be modified to cope with private CPU interrupts, > which are controlled individually by their associated CPU, or we need a > private interface to support this. I see your point. Our immediate need for this is to support a performance monitor interrupt that happens to be a PPI. It is used by perf events (and subsequently, oprofile). Since PPIs are so machine-specific, I started looking into patching perf_events.c by adding a machine specific function to handle the PMU IRQ request. For mach-msm, we would call request_irq like normal, but also unmask the performance monitor interrupt on the other cores. The downside to this is that a machine specific implementation would be needed anytime a PPI is requested, not just in perf_events.c. Then, I saw Thomas' email regarding our local timer PPI: http://lists.infradead.org/pipermail/linux-arm-kernel/2010-December/033840.html. Russell, before I submit another patch, I would like to know if you prefer a more generic approach like Thomas suggests, or a machine-specific approach like I have described? Thanks, Stephen -- Sent by a consultant of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html