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: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -12,6 +12,7 @@
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#include <linux/string.h>
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#include <linux/pci.h>
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#include <linux/module.h>
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#include <linux/pci.h>
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#include <asm/io.h>
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struct dma_coherent_mem {
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@ -148,3 +149,29 @@ void *dma_mark_declared_memory_occupied(struct device *dev,
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return mem->virt_base + (pos << PAGE_SHIFT);
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}
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EXPORT_SYMBOL(dma_mark_declared_memory_occupied);
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#ifdef CONFIG_PCI
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/* Many VIA bridges seem to corrupt data for DAC. Disable it here */
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int forbid_dac;
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EXPORT_SYMBOL(forbid_dac);
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static __devinit void via_no_dac(struct pci_dev *dev)
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{
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if ((dev->class >> 8) == PCI_CLASS_BRIDGE_PCI && forbid_dac == 0) {
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printk(KERN_INFO "PCI: VIA PCI bridge detected. Disabling DAC.\n");
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forbid_dac = 1;
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}
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}
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DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID, via_no_dac);
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static int check_iommu(char *s)
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{
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if (!strcmp(s, "usedac")) {
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forbid_dac = -1;
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return 1;
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}
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return 0;
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}
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__setup("iommu=", check_iommu);
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#endif
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@ -322,5 +322,17 @@ static int __init pci_iommu_init(void)
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return 0;
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}
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#ifdef CONFIG_PCI
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/* Many VIA bridges seem to corrupt data for DAC. Disable it here */
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static __devinit void via_no_dac(struct pci_dev *dev)
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{
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if ((dev->class >> 8) == PCI_CLASS_BRIDGE_PCI && forbid_dac == 0) {
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printk(KERN_INFO "PCI: VIA PCI bridge detected. Disabling DAC.\n");
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forbid_dac = 1;
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}
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}
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DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID, via_no_dac);
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#endif
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/* Must execute after PCI subsystem */
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fs_initcall(pci_iommu_init);
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@ -123,6 +123,8 @@ dma_mapping_error(dma_addr_t dma_addr)
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return 0;
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}
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extern int forbid_dac;
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static inline int
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dma_supported(struct device *dev, u64 mask)
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{
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@ -134,6 +136,10 @@ dma_supported(struct device *dev, u64 mask)
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if(mask < 0x00ffffff)
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return 0;
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/* Work around chipset bugs */
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if (forbid_dac > 0 && mask > 0xffffffffULL)
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return 0;
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return 1;
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}
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