Hi all, boot interrupts are a major pain for linux interrupt handling. I'm not going into detail here, explaining it all over again. In case you want to know more refer to the links below. http://lkml.org/lkml/2009/9/4/350 http://lkml.org/lkml/2008/6/2/269 http://people.redhat.com/sassmann/publications/boot_irq_quirks_rtlws10.pdf http://people.redhat.com/sassmann/publications/Boot_Interrupts_and_IRQ_Threads.pdf While we're still fighting this chipset generations boot interrupts there's something we can do to prevent next gens chipsets from generating these. Therefore we need support from BIOS people. In fact ACPI has a method to "report to the BIOS the current interrupt model used by the OS"¹. That method is called _PIC. So calling _PIC(1) tells the BIOS the OS has chosen to run in APIC mode and gives the BIOS the possibility to make adjustments. Now that is where the BIOS should _disable_ all sources of boot interrupts. As the implementation of how to disable boot interrupts is really chipset specific it's the BIOSes task to disable them in the APIC mode case. All the boot interrupt quirks we've been adding to the kernel are just workarounds for buggy BIOSes! An example of how this can look like, taken from the AMD SB700/710/750 BIOS developers guide²: During the BIOS POST, the BIOS will do normal PCI IRQ routing through port C00h/C01h. Once APIC is fully enabled by the OS, the routing in C00h/C01 must be all cleared to zero. The following is a sample ASL code that may be incorporated into the BIOS: Name(PICF,0x00) Method(_PIC, 0x01, NotSerialized) { Store (Arg0, PICF) If(Arg0) { \_SB.PCI0.LPC0.DSPI() // clear interrupt at 0xC00/0xC01 } } [...] (full implementation snipped) Note: 0xC00/0xC01 are the PCI interrupt mapping registers in this case. It's not that hard to do once you're aware of it. This is a call to all chipset manufacturers/BIOS developers/everyone involved: Please get the appropriate changes into your BIOS/BIOS developers guide! Thanks! ¹ ACPI Specification 4.0 (sec 5.8.1) ² http://developer.amd.com/assets/43366_sb7xx_bdg_pub_1.00.pdf (sec 10.5) Stefan -- Stefan Assmann | Red Hat GmbH Software Engineer | Otto-Hahn-Strasse 20, 85609 Dornach | HR: Amtsgericht Muenchen HRB 153243 | GF: Brendan Lane, Charlie Peters, sassmann at redhat.com | Michael Cunningham, Charles Cachera -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
