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authorNatalie Protasevich <Natalie.Protasevich@unisys.com>2005-06-23 00:08:29 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-23 09:45:10 -0700
commitc434b7a6aedfe428ad17cd61b21b125a7b7a29ce (patch)
tree1b1fb9d7279e715b765d8a4dd8a439166d68c516 /arch
parentb5d23e5b8c7ecd97d32f6ad7680d9909977580a7 (diff)
[PATCH] x86: avoid wasting IRQs for PCI devices
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/i386/kernel/mpparse.c26
1 files changed, 25 insertions, 1 deletions
diff --git a/arch/i386/kernel/mpparse.c b/arch/i386/kernel/mpparse.c
index 0a061056b828..383a11600d2c 100644
--- a/arch/i386/kernel/mpparse.c
+++ b/arch/i386/kernel/mpparse.c
@@ -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);