Messages in this thread | | | From | Ondrej Zary <> | Subject | Re: Non-requested PCI IRQs unavailable to ISA PnP devices and pci_dev_uses_irq() | Date | Sat, 13 Jun 2009 00:08:55 +0200 |
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On Friday 12 June 2009 22:38:17 you wrote: > On Friday 12 June 2009 01:43:57 pm Ondrej Zary wrote: > > Hello, > > some PCI devices have an IRQ but the driver does not use it. Such an > > example is matroxfb. It does request_irq() only for some vblank > > operations. Thus, the irq is not marked as used in /proc/interrupts: > > CPU0 > > 0: 246481 XT-PIC-XT timer > > 1: 3507 XT-PIC-XT i8042 > > 2: 0 XT-PIC-XT cascade > > 3: 1 XT-PIC-XT > > 4: 1 XT-PIC-XT > > 5: 4306 XT-PIC-XT eth0 > > 6: 5 XT-PIC-XT floppy > > 7: 1 XT-PIC-XT parport0 > > 8: 1 XT-PIC-XT rtc > > 9: 0 XT-PIC-XT acpi > > 11: 13748 XT-PIC-XT pata_it821x, uhci_hcd:usb1 > > 12: 65539 XT-PIC-XT i8042 > > 14: 0 XT-PIC-XT ata_piix > > 15: 33052 XT-PIC-XT ata_piix > > NMI: 0 Non-maskable interrupts > > ERR: 0 > > > > IRQ 10 is not listed but is used by one of the two Matrox cards: > > > > pci 0000:00:13.0: Boot video device > > ACPI: PCI Interrupt Link [LNKB] enabled at IRQ 11 > > PCI: setting IRQ 11 as level-triggered > > matroxfb 0000:00:13.0: PCI INT A -> Link[LNKB] -> GSI 11 (level, low) -> > > IRQ 11 > > matroxfb: Matrox Mystique (PCI) detected > > PInS memtype = 0 > > matroxfb: MTRR's turned on > > matroxfb: 1024x768x8bpp (virtual: 1024x4096) > > matroxfb: framebuffer at 0xE1000000, mapped to 0xd0880000, size 4194304 > > Console: switching to colour frame buffer device 128x48 > > fb0: MATROX frame buffer device > > matroxfb 0000:00:14.0: enabling device (0000 -> 0002) > > ACPI: PCI Interrupt Link [LNKA] enabled at IRQ 10 > > PCI: setting IRQ 10 as level-triggered > > matroxfb 0000:00:14.0: PCI INT A -> Link[LNKA] -> GSI 10 (level, low) -> > > IRQ 10 > > matroxfb: Matrox Millennium II (PCI) detected > > PInS memtype = 0 > > matroxfb: MTRR's turned on > > matroxfb: 1024x768x8bpp (virtual: 1024x4096) > > matroxfb: framebuffer at 0xE3000000, mapped to 0xd1100000, size 4194304 > > fb1: MATROX frame buffer device > > fb1: initializing hardware > > > > > > But this interrupt is not available to ISA PnP devices because > > drivers/pnp/resource.c calls pci_uses_irq() function which in turn calls > > pci_dev_uses_irq() for all PCI devices. pci_dev_uses_irq() simply checks > > the irq field in struct pci_dev. > > > > I wonder if that's correct (is it a bug or a feature)? > > The code that tries to keep PCI and PNP IRQs from clashing is > definitely sub-optimal. Of course, PNP doesn't know what the > matroxfb driver doesn't need the interrupt. Some drivers request > and free the IRQ dynamically, depending on whether the device is > in use. > > Maybe what we should be doing here is more sharing of PCI interrupts > to leave more available for PNP. For example, the 00:14.0 device > that's currently using IRQ 10 is connected to a programmable IRQ > link (LNKA). Possibly that link could be programmed to share IRQ 11 > instead. > > In the absence of an automatic mechanism, can you work around this > with the "acpi_irq_isa=10" kernel parameter?
Great, it works - both matrox cards are now at IRQ 11. Thanks for suggestion. Although it should not work according do Documentation/kernel-parameters.txt:
acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA Format: <irq>,<irq>...
But this should apply to my machine: acpi_irq_nobalance [HW,ACPI] ACPI will not move active IRQs (default) default in PIC mode
> > Bjorn > > > I can't use CMI8239A sound card on my machine because of this (it needs > > two IRQs). When I comment out that check (and move eth0 to IRQ3), the > > sound card works, allocating IRQ 10 and 3 (with some modifications to > > cmi8330 driver - will be posted separately).
-- Ondrej Zary
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