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[PATCH] Allow disabling DAC using command line options 

Might or might not work around some reported bugs on VIA systems.

Signed-off-by: Andi Kleen <ak@suse.de>
This commit is contained in:
Andi Kleen 2006-09-30 01:47:55 +02:00 committed by Andi Kleen
parent b885808e18
commit ece6684012
2 changed files with 22 additions and 0 deletions
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4
Documentation/x86_64/boot-options.txt
View File

@ -199,6 +199,10 @@ IOMMU
allowed overwrite iommu off workarounds for specific chipsets.
soft Use software bounce buffering (default for Intel machines)
noaperture Don't touch the aperture for AGP.
allowdac Allow DMA >4GB
When off all DMA over >4GB is forced through an IOMMU or bounce
buffering.
nodac Forbid DMA >4GB
swiotlb=pages[,force]

18
arch/x86_64/kernel/pci-dma.c
View File

@ -170,8 +170,20 @@ void dma_free_coherent(struct device *dev, size_t size,
}
EXPORT_SYMBOL(dma_free_coherent);
static int forbid_dac __read_mostly;
int dma_supported(struct device *dev, u64 mask)
{
#ifdef CONFIG_PCI
if (mask > 0xffffffff && forbid_dac > 0) {
printk(KERN_INFO "PCI: Disallowing DAC for device %s\n", dev->bus_id);
return 0;
}
#endif
if (dma_ops->dma_supported)
return dma_ops->dma_supported(dev, mask);
@ -231,6 +243,8 @@ EXPORT_SYMBOL(dma_set_mask);
allowed overwrite iommu off workarounds for specific chipsets.
soft Use software bounce buffering (default for Intel machines)
noaperture Don't touch the aperture for AGP.
allowdac Allow DMA >4GB
nodac Forbid DMA >4GB
*/
__init int iommu_setup(char *p)
{
@ -267,6 +281,10 @@ __init int iommu_setup(char *p)
iommu_merge = 0;
if (!strncmp(p, "forcesac",8))
iommu_sac_force = 1;
if (!strncmp(p, "allowdac", 8))
forbid_dac = 0;
if (!strncmp(p, "nodac", 5))
forbid_dac = -1;
#ifdef CONFIG_SWIOTLB
if (!strncmp(p, "soft",4))