Most interrupts are edge-triggered, non-APIC system

[Daniel Drake <dsd@gentoo.org>]

Hi,

João Oliveirinha reported a bug related to the sky2 network driver on 
the Gentoo bugzilla. Stephen Hemminger (sky2 author) kindly helped 
diagnose the issues, and he believes that one of the reasons why things 
are running sub-optimally is because the interrupt assigned to sky2 is 
edge-triggered (NAPI requires things to be level-triggered).

The system is a bit odd in that even on the latest BIOS, APIC support is 
apparently completely non-functional (or maybe just non-existent?). Even 
when the "lapic" parameter is used, ACPI appears to be used exclusively 
for interrupt routing.

This is a Toshiba M40-298 laptop.

Here is the interrupts map:

            CPU0
   0:      47094          XT-PIC  timer
   1:        541          XT-PIC  i8042
   2:          0          XT-PIC  cascade
   9:         13          XT-PIC  acpi
  10:       5548          XT-PIC  ehci_hcd:usb1, uhci_hcd:usb2, Intel ICH6
  11:         27          XT-PIC  uhci_hcd:usb3, uhci_hcd:usb4, 
uhci_hcd:usb5, yenta, sdhci:slot0, sdhci:slot1, sdhci:slot2, ohci1394, sky2
  12:        618          XT-PIC  i8042
  14:       7384          XT-PIC  libata
  15:       1275          XT-PIC  libata
NMI:          0
LOC:          0
ERR:          0
MIS:          0

And the ELCR register:
	ACPI: setting ELCR to 0200 (from 0c20)

0200 suggests that IRQ 9 is the only level-triggered interrupt. Also, 
the interrupts are heavily shared, I'm not sure if this is another 
reason for concern...

Anyway, I'm not too familiar with ACPI or interrupt routing, so: do you 
regard it as a bug that so many interrupts are level-triggered?

If so, we can get it filed at the kernel bugzilla if appropriate.

Here is some info that might be useful:

dmesg dump with ACPI debugging enabled:
http://bugs.gentoo.org/attachment.cgi?id=85619&action=view

dmesg with the lapic parameter used at boot:
https://bugs.gentoo.org/attachment.cgi?id=85540&action=view

acpidump:
https://bugs.gentoo.org/attachment.cgi?id=85685&action=view

The actual bug report:
http://bugs.gentoo.org/show_bug.cgi?id=131274

Thanks,
Daniel
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