commit c434b7a6ae
(x86: avoid wasting IRQs for PCI devices)
created a concept of "IRQ compression" on i386
to conserve IRQ numbers on systems with many
sparsely populated IO APICs.
The same scheme was also added to x86_64,
but later removed when x86_64 recieved an IRQ over-haul
that made it unnecessary -- including per-CPU
IRQ vectors that greatly increased the IRQ capacity
on the machine.
i386 has not received the analogous over-haul,
and thus a previous attempt to delete IRQ compression
from i386 was rejected on the theory that there may
exist machines that actually need it. The fact is
that the author of IRQ compression patch was unable
to confirm the actual existence of such a system.
As a result, all i386 kernels with IOAPIC support
pay the following:
1. confusion
IRQ compression re-names the traditional IOAPIC
pin numbers (aka ACPI GSI's) into sequential IRQ #s:
ACPI: PCI Interrupt 0000:00:1c.0[A] -> GSI 20 (level, low) -> IRQ 16
ACPI: PCI Interrupt 0000:00:1c.1[B] -> GSI 21 (level, low) -> IRQ 17
ACPI: PCI Interrupt 0000:00:1c.2[C] -> GSI 22 (level, low) -> IRQ 18
ACPI: PCI Interrupt 0000:00:1c.3[D] -> GSI 23 (level, low) -> IRQ 19
ACPI: PCI Interrupt 0000:00:1c.4[A] -> GSI 20 (level, low) -> IRQ 16
This makes /proc/interrupts look different
depending on system configuration and device probe order.
It is also different than the x86_64 kernel running
on the exact same system. As a result, programmers
get confused when comparing systems.
2. complexity
The IRQ code in Linux is already overly complex,
and IRQ compression makes it worse. There have
already been two bug workarounds related to IRQ
compression -- the IRQ0 timer workaround and
the VIA PCI IRQ workaround.
3. size
All i386 kernels with IOAPIC support contain an int[4096] --
a 4 page array to contain the renamed IRQs.
So while the irq compression code on i386 should really
be deleted -- even before merging the x86_64 irq-overhaul,
this patch simply disables it on all high volume systems
to avoid problems #1 and #2 on most all i386 systems.
A large system with pin numbers >=64 will still have compression
to conserve limited IRQ numbers for sparse IOAPICS. However,
the vast majority of the planet, those with only pin numbers < 64
will use an identity GSI -> IRQ mapping.
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Need to check for special case "acpi_osi=!Linux" before handling the
general case "acpi_osi=!*", or it will have no effect.
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
x86_64 nvidia_bugs() broke when we bailed out on not finding the HPET.
However, the quirk works by checking for _not_ finding the HPET...
Delete the nvidia_hpet_detected flag and simply test for
not finding the HPET, which is simple to do now that
acpi_table_parse returns 1 on failure.
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
All IA64 systems except IA64_HP_SIM include ACPI and PCI.
So prevent IA64 Kconfigs that try to do irritating things like building
PCI without building ACPI.
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Len Brown