Messages in this thread | | | Subject | RE: [(repost) git Patch 1/1] avoid IRQ0 ioapic pin collision | Date | Thu, 4 May 2006 01:07:29 -0400 | From | "Brown, Len" <> |
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>>> We should never have had a problem with un-connected interrupt lines >>> consuming vectors, as the vectors are handed out at run-time >>> only when interrupts are requested by drivers. >> >>Incorrect. By being requested by drivers I assume you mean by >>request_irq. assign_irq_vector is called long before request_irq >>and in fact there is currently not a call from request_irq to >>assign_irq_vector. Look where assign_irq_vector is called in >io_apic.c
Hmmm, on Natalie's ping, I looked at this again.
setup_IO_APIC_irqs() actually consumes only 16 vectors. This is because it only sets up the IRQs for pins found with find_irq_entry(), which searches mp_irqs[] which at this point contains only the legacy identify mappings.
The PNP code then takes a swing at things, and it registers a handful of gsi's, but they are all duplicates of the legacy mappings already set-up, so no additional vectors are consumed.
So on a big system, the large quantity of vectors will not be consumed at IOAPIC initialization time, but later at device probe time. Not via request_irq(), but via pci_enable_device():
pci_enable_device() pci_enable_device_bars() pcibios_enable_device() pcibios_enable_irq() -> acpi_pci_irq_enable() acpi_register_gsi() mp_register_gsi() io_apic_set_pci_routing() entry.vector = assign_irq_vector(irq)
So except for the legacy IRQs, we are already allocating the vectors on-demand, and that doesn't need to be fixed.
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