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Commit 388c19e1 authored by Andi Kleen's avatar Andi Kleen Committed by Linus Torvalds
Browse files

x86: Disable DAC on VIA bridges 



Several reports that VIA bridges don't support DAC and corrupt
data.  I don't know if it's fixed, but let's just blacklist
them all for now.

It can be overwritten with iommu=usedac

Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0b622330

arch/i386/kernel/pci-dma.c

+27 −0
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/string.h>

#include <linux/pci.h>

#include <linux/module.h>

#include <linux/pci.h>

#include <asm/io.h>



struct dma_coherent_mem {
@@ -148,3 +149,29 @@ void *dma_mark_declared_memory_occupied(struct device *dev, 
	return mem->virt_base + (pos << PAGE_SHIFT);

}

EXPORT_SYMBOL(dma_mark_declared_memory_occupied);



#ifdef CONFIG_PCI

/* Many VIA bridges seem to corrupt data for DAC. Disable it here */



int forbid_dac;

EXPORT_SYMBOL(forbid_dac);



static __devinit void via_no_dac(struct pci_dev *dev)

{

	if ((dev->class >> 8) == PCI_CLASS_BRIDGE_PCI && forbid_dac == 0) {

		printk(KERN_INFO "PCI: VIA PCI bridge detected. Disabling DAC.\n");

		forbid_dac = 1;

	}

}

DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID, via_no_dac);



static int check_iommu(char *s)

{

	if (!strcmp(s, "usedac")) {

		forbid_dac = -1;

		return 1;

	}

	return 0;

}

__setup("iommu=", check_iommu);

#endif

arch/x86_64/kernel/pci-dma.c

+12 −0
Original line number Diff line number Diff line
@@ -322,5 +322,17 @@ static int __init pci_iommu_init(void) 
	return 0;

}



#ifdef CONFIG_PCI

/* Many VIA bridges seem to corrupt data for DAC. Disable it here */



static __devinit void via_no_dac(struct pci_dev *dev)

{

	if ((dev->class >> 8) == PCI_CLASS_BRIDGE_PCI && forbid_dac == 0) {

		printk(KERN_INFO "PCI: VIA PCI bridge detected. Disabling DAC.\n");

		forbid_dac = 1;

	}

}

DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID, via_no_dac);

#endif

/* Must execute after PCI subsystem */

fs_initcall(pci_iommu_init);

include/asm-i386/dma-mapping.h

+6 −0
Original line number Diff line number Diff line
@@ -123,6 +123,8 @@ dma_mapping_error(dma_addr_t dma_addr) 
	return 0;

}



extern int forbid_dac;



static inline int

dma_supported(struct device *dev, u64 mask)

{
@@ -134,6 +136,10 @@ dma_supported(struct device *dev, u64 mask) 
        if(mask < 0x00ffffff)

                return 0;



	/* Work around chipset bugs */

	if (forbid_dac > 0 && mask > 0xffffffffULL)

		return 0;



	return 1;

}