Radeon RV100 init fails with specific card+mobo - IRQ problem

[Alex Deucher]

On Mon, Feb 4, 2013 at 11:32 AM, Meelis Roos <mroos at linux.ee> wrote:
>> >> > Adding some printks reveals it calls
>> >> > r100_init() -> radeon_irq_kms_init() -> drm_irq_install() ->
>> >> > drm_dev_to_irq() and that fails. So no IRQ, no KMS.
>> >> >
>> >> > lspci does not show Interrupt like on some other PCI devices.
>> >> > /proc/interrupts obviously does not contain the irq since we do not
>> >> > register any yet.
>> >> >
>> >> > There is no BIOS option of "Enable IRQ for VGA" or similar (BIOS is
>> >> > latest). Could this be the problem?
>> >> >
>> >> > What can I do to get KMS working on this computer?
>> >> >
>> >> > --
>> >> > Meelis Roos (mroos at linux.ee)
>> >>
>> >> Try booting with radeon.agp_mode=-1
>> >
>> > radeon: `-1' invalid for parameter `agp_mode'
>>
>> radeon.agpmode=-1
>>
>> However, I think there are a number of places where we require
>> interrupts that would need to be worked around (fences, display
>> hotplug, pageflipping) if not interrupt is available.
>
> I did dome more testing with different cards an got a surprise. The
> machine works fine with other AGP cards - one MX440 with nouvea, another
> RV100 QY and a R200. They do have interrupt in lspci -vvv output.
>
> Why does this specific card not have its IRQ routed - card ROM problem?

For some reason the system bios on your box doesn't assign it one.
The video bios isn't really involved.  I'm not sure if there is a way
to force assign an irq in Linux or not.

Alex