From 388c19e176436707eb30a81c7e4129e08769f92b Mon Sep 17 00:00:00 2001 From: Andi Kleen <ak@suse.de> Date: Wed, 20 Jun 2007 12:23:32 +0200 Subject: 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> --- include/asm-i386/dma-mapping.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include') diff --git a/include/asm-i386/dma-mapping.h b/include/asm-i386/dma-mapping.h index 183eebeebbdc..f1d72d177f68 100644 --- a/include/asm-i386/dma-mapping.h +++ b/include/asm-i386/dma-mapping.h @@ -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; } -- cgit v1.2.3