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[PATCH] x86: avoid wasting IRQs for PCI devices

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I have submitted the patch for x86_64, this is submission for i386.

The patch changes the way IRQs are handed out to PCI devices.  Currently,
each I/O APIC pin gets associated with an IRQ, no matter if the pin is used
or not.  This imposes severe limitation on systems that have designs that
employ many I/O APICs, only utilizing couple lines of each, such as P64H2
chipset.  It is used in ES7000, and currently, there is no way to boot the
system with more that 9 I/O APICs.

The simple change below allows to boot a system with say 64 (or more) I/O
APICs, each providing 1 slot, which otherwise impossible because of the IRQ
gaps created for unused lines on each I/O APIC.  It does not resolve the
problem with number of devices that exceeds number of possible IRQs, but
eases up a tension for IRQs on any large system with potentually large
number of devices.

Signed-off-by: Natalie Protasevich <Natalie.Protasevich@unisys.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Natalie Protasevich 2005-06-23 00:08:29 -07:00 committed by Linus Torvalds
parent b5d23e5b8c
commit c434b7a6ae
1 changed files with 25 additions and 1 deletions
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26
arch/i386/kernel/mpparse.c
View file

@ -1058,11 +1058,20 @@ void __init mp_config_acpi_legacy_irqs (void)
}
}
#define MAX_GSI_NUM 4096
int mp_register_gsi (u32 gsi, int edge_level, int active_high_low)
{
int ioapic = -1;
int ioapic_pin = 0;
int idx, bit = 0;
static int pci_irq = 16;
/*
* Mapping between Global System Interrups, which
* represent all possible interrupts, and IRQs
* assigned to actual devices.
*/
static int gsi_to_irq[MAX_GSI_NUM];
#ifdef CONFIG_ACPI_BUS
/* Don't set up the ACPI SCI because it's already set up */
@ -1097,11 +1106,26 @@ int mp_register_gsi (u32 gsi, int edge_level, int active_high_low)
if ((1<<bit) & mp_ioapic_routing[ioapic].pin_programmed[idx]) {
Dprintk(KERN_DEBUG "Pin %d-%d already programmed\n",
mp_ioapic_routing[ioapic].apic_id, ioapic_pin);
return gsi;
return gsi_to_irq[gsi];
}
mp_ioapic_routing[ioapic].pin_programmed[idx] |= (1<<bit);
if (edge_level) {
/*
* For PCI devices assign IRQs in order, avoiding gaps
* due to unused I/O APIC pins.
*/
int irq = gsi;
if (gsi < MAX_GSI_NUM) {
gsi = pci_irq++;
gsi_to_irq[irq] = gsi;
} else {
printk(KERN_ERR "GSI %u is too high\n", gsi);
return gsi;
}
}
io_apic_set_pci_routing(ioapic, ioapic_pin, gsi,
edge_level == ACPI_EDGE_SENSITIVE ? 0 : 1,
active_high_low == ACPI_ACTIVE_HIGH ? 0 : 1);