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[PATCH] via vt8237 apic bypass deassertion quirk

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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>
This commit is contained in:
Karsten Wiese 2005-09-03 15:56:33 -07:00 committed by Linus Torvalds
parent 252943efcf
commit a1740913ca
1 changed files with 19 additions and 0 deletions
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19
drivers/pci/quirks.c
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@ -421,6 +421,25 @@ 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