Bug 2742

Summary:	ACPI SCI may not work in IOAPIC mode with acpi=noirq or pci=noacpi
Product:	ACPI	Reporter:	Len Brown (lenb)
Component:	Config-Interrupts	Assignee:	acpi_config-interrupts
Status:	REJECTED WILL_NOT_FIX
Severity:	normal	CC:	acpi-bugzilla
Priority:	P2
Hardware:	i386
OS:	Linux
Kernel Version:	2.6.6	Subsystem:
Regression:	---	Bisected commit-id:

Description Len Brown 2004-05-20 19:12:24 UTC

Booting the kernel with "acpi=noirq" or "pci=noirq" disables ACPI's 
interrupt configuration code. 
 
If the system has no IOAPIC, or if it has an IOAPIC but has no 
MPS tables, then it will run in PIC mode. 
In PIC mode, the ACPI SCI should still function properly. 
 
But if the system has an IOAPIC and MPS, then it is at the mercy 
of MPS if the ACPI interrupt is going to work or not. 
ACPI will continue to request_irq() on the FADT.SCI_INT.  However, 
this IRQ# may be incorrect for IOAPIC mode, or its polarity/trigger 
may be incorrect -- and the ACPI code that processes the 
MADT interrupt source override to customize this IRQ for IOAPIC 
mode does not correct it.  In this case, the ACPI SCI may or may 
not work, depending on if the MPS tables happen to set up the 
interrupt in the way that the ACPI hardwar expects it to be set up.

Comment 1 Len Brown 2004-05-20 19:16:46 UTC

acpi=noirq and pci=noacpi are workarounds for BIOS or Linux ACPI interrupt 
configuration bugs. 
 
Rather than complicate the code for the benefit of the workarounds, 
the focus should be on fixing the root cause issues that require these 
workarounds in the first place.  So I'm closing this bug as WILL_NOT_FIX. 
 
Note, if your system requires these workarounds and you really want 
ACPI interrupts, then you can add "noapic" to run in PIC mode and 
the SCI should work that way.