* Non-requested PCI IRQs unavailable to ISA PnP devices and pci_dev_uses_irq()
@ 2009-06-12 19:43 Ondrej Zary
2009-06-12 20:38 ` Bjorn Helgaas
0 siblings, 1 reply; 3+ messages in thread
From: Ondrej Zary @ 2009-06-12 19:43 UTC (permalink / raw)
To: abelay, bjorn.helgaas, linux-kernel
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)?
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
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: Non-requested PCI IRQs unavailable to ISA PnP devices and pci_dev_uses_irq()
2009-06-12 19:43 Non-requested PCI IRQs unavailable to ISA PnP devices and pci_dev_uses_irq() Ondrej Zary
@ 2009-06-12 20:38 ` Bjorn Helgaas
2009-06-12 22:08 ` Ondrej Zary
0 siblings, 1 reply; 3+ messages in thread
From: Bjorn Helgaas @ 2009-06-12 20:38 UTC (permalink / raw)
To: Ondrej Zary; +Cc: abelay, linux-kernel
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?
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).
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Non-requested PCI IRQs unavailable to ISA PnP devices and pci_dev_uses_irq()
2009-06-12 20:38 ` Bjorn Helgaas
@ 2009-06-12 22:08 ` Ondrej Zary
0 siblings, 0 replies; 3+ messages in thread
From: Ondrej Zary @ 2009-06-12 22:08 UTC (permalink / raw)
To: Bjorn Helgaas; +Cc: abelay, linux-kernel
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
^ permalink raw reply [flat|nested] 3+ messages in thread
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2009-06-12 19:43 Non-requested PCI IRQs unavailable to ISA PnP devices and pci_dev_uses_irq() Ondrej Zary
2009-06-12 20:38 ` Bjorn Helgaas
2009-06-12 22:08 ` Ondrej Zary
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