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authorKarsten Wiese <annabellesgarden@yahoo.de>2005-09-03 15:56:33 -0700
committerLinus Torvalds <torvalds@evo.osdl.org>2005-09-05 00:06:10 -0700
commita1740913cae231fb8e485306fb09671ed9a6e550 (patch)
tree60cde26b254d6df2433016cfa1f328b59b00b828 /drivers/pci
parent252943efcfce945d8dd3738ca4c4b9cbeb4f3fa9 (diff)
[PATCH] via vt8237 apic bypass deassertion quirk
The VIA VT8237's IOAPIC sends 'APIC De-Assert Messages' by default, causing another CPU interrupt when the IRQ pin is de-asserted. This feature is switched off by the patch to get rid of doubled ioapic level interrupt rates. Signed-off-by: Karsten Wiese <annabellesgarden@yahoo.de> Tested-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/pci')
-rw-r--r--drivers/pci/quirks.c19
1 files changed, 19 insertions, 0 deletions
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index bb36bb69803f..140354a2aa72 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -422,6 +422,25 @@ static void __devinit quirk_via_ioapic(struct pci_dev *dev)
DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_VIA, PCI_DEVICE_ID_VIA_82C686, quirk_via_ioapic );
/*
+ * VIA 8237: Some BIOSs don't set the 'Bypass APIC De-Assert Message' Bit.
+ * This leads to doubled level interrupt rates.
+ * Set this bit to get rid of cycle wastage.
+ * Otherwise uncritical.
+ */
+static void __devinit quirk_via_vt8237_bypass_apic_deassert(struct pci_dev *dev)
+{
+ u8 misc_control2;
+#define BYPASS_APIC_DEASSERT 8
+
+ pci_read_config_byte(dev, 0x5B, &misc_control2);
+ if (!(misc_control2 & BYPASS_APIC_DEASSERT)) {
+ printk(KERN_INFO "PCI: Bypassing VIA 8237 APIC De-Assert Message\n");
+ pci_write_config_byte(dev, 0x5B, misc_control2|BYPASS_APIC_DEASSERT);
+ }
+}
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_VIA, PCI_DEVICE_ID_VIA_8237, quirk_via_vt8237_bypass_apic_deassert);
+
+/*
* The AMD io apic can hang the box when an apic irq is masked.
* We check all revs >= B0 (yet not in the pre production!) as the bug
* is currently marked NoFix