Introduce intel_iommu=forcedac commandline option. This option is helpful to verify the pci device capability of handling physical dma'able address greater than 4G. Signed-off-by: Anil S Keshavamurthy --- Documentation/kernel-parameters.txt | 7 +++++++ drivers/pci/intel-iommu.c | 6 +++++- 2 files changed, 12 insertions(+), 1 deletion(-) Index: linux-2.6.22-rc3/Documentation/kernel-parameters.txt =================================================================== --- linux-2.6.22-rc3.orig/Documentation/kernel-parameters.txt 2007-06-04 12:40:29.000000000 -0700 +++ linux-2.6.22-rc3/Documentation/kernel-parameters.txt 2007-06-04 12:40:41.000000000 -0700 @@ -785,6 +785,13 @@ bypassed by not enabling DMAR with this option. In this case, gfx device will use physical address for DMA. + forcedac + With this option iommu will not optimize to look + for io virtual address below 32 bit forcing dual + address cycle on pci bus for cards supporting greater + than 32 bit addressing. The default is to look + for translation below 32 bit and if not available + then look in the higher range. io7= [HW] IO7 for Marvel based alpha systems See comment before marvel_specify_io7 in Index: linux-2.6.22-rc3/drivers/pci/intel-iommu.c =================================================================== --- linux-2.6.22-rc3.orig/drivers/pci/intel-iommu.c 2007-06-04 12:40:29.000000000 -0700 +++ linux-2.6.22-rc3/drivers/pci/intel-iommu.c 2007-06-04 12:40:41.000000000 -0700 @@ -53,6 +53,7 @@ static int dmar_disabled; static int __initdata dmar_map_gfx = 1; +static int dmar_forcedac = 0; #define DUMMY_DEVICE_DOMAIN_INFO ((struct device_domain_info *)(-1)) static DEFINE_SPINLOCK(device_domain_lock); @@ -69,6 +70,9 @@ } else if (!strncmp(str, "igfx_off", 8)) { dmar_map_gfx = 0; printk(KERN_INFO"Intel-IOMMU: disable GFX device mapping\n"); + } else if (!strncmp(str, "forcedac", 8)) { + printk (KERN_INFO"Intel-IOMMU: Enabling DAC for PCI supporting > 32Bit DMA\n"); + dmar_forcedac = 1; } str += strcspn(str, ","); @@ -1500,7 +1504,7 @@ start_addr = IOVA_START_ADDR; - if (pdev->dma_mask <= DMA_32BIT_MASK) { + if ((pdev->dma_mask <= DMA_32BIT_MASK) || (dmar_forcedac)) { iova = iommu_alloc_iova(domain, addr, size, start_addr, pdev->dma_mask); } else { -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/