[Intel-IOMMU 07/10] Intel iommu cmdline option - forcedac

[anil . s . keshavamurthy]

	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 <anil.s.keshavamurthy@xxxxxxxxx>
---
 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  {

-- 
-
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