diff -r cfdb02b1450e Documentation/x86_64/boot-options.txt
--- a/Documentation/x86_64/boot-options.txt	Sun Oct 29 09:25:34 2006 +0200
+++ b/Documentation/x86_64/boot-options.txt	Sun Oct 29 10:55:18 2006 +0200
@@ -183,7 +183,7 @@ IOMMU
 IOMMU
 
  iommu=[size][,noagp][,off][,force][,noforce][,leak][,memaper[=order]][,merge]
-         [,forcesac][,fullflush][,nomerge][,noaperture]
+         [,forcesac][,fullflush][,nomerge][,noaperture][,calgary]
    size  set size of iommu (in bytes)
    noagp don't initialize the AGP driver and use full aperture.
    off   don't use the IOMMU
@@ -204,6 +204,7 @@ IOMMU
 	    buffering.
    nodac    Forbid DMA >4GB
    panic    Always panic when IOMMU overflows
+   calgary  Use the Calgary IOMMU if it is available
 
   swiotlb=pages[,force]
 
diff -r cfdb02b1450e arch/x86_64/Kconfig
--- a/arch/x86_64/Kconfig	Sun Oct 29 09:25:34 2006 +0200
+++ b/arch/x86_64/Kconfig	Sun Oct 29 10:55:00 2006 +0200
@@ -455,6 +455,17 @@ config CALGARY_IOMMU
 	  Normally the kernel will make the right choice by itself.
 	  If unsure, say Y.
 
+config CALGARY_IOMMU_ENABLED_BY_DEFAULT
+	bool "Should Calgary be enabled by default?"
+	default y
+	depends on CALGARY_IOMMU
+	help
+	  Should Calgary be enabled by default? if you choose 'y', Calgary
+	  will be used (if it exists). If you choose 'n', Calgary will not be
+	  used even if it exists. If you choose 'n' and would like to use
+	  Calgary anyway, pass 'iommu=calgary' on the kernel command line.
+	  If unsure, say Y.
+
 # need this always selected by IOMMU for the VIA workaround
 config SWIOTLB
 	bool
diff -r cfdb02b1450e arch/x86_64/kernel/pci-calgary.c
--- a/arch/x86_64/kernel/pci-calgary.c	Sun Oct 29 09:25:34 2006 +0200
+++ b/arch/x86_64/kernel/pci-calgary.c	Sun Oct 29 10:55:00 2006 +0200
@@ -41,6 +41,12 @@
 #include <asm/pci-direct.h>
 #include <asm/system.h>
 #include <asm/dma.h>
+
+#ifdef CONFIG_CALGARY_IOMMU_ENABLED_BY_DEFAULT
+int use_calgary __read_mostly = 1;
+#else
+int use_calgary __read_mostly = 0;
+#endif /* CONFIG_CALGARY_DEFAULT_ENABLED */
 
 #define PCI_DEVICE_ID_IBM_CALGARY 0x02a1
 #define PCI_VENDOR_DEVICE_ID_CALGARY \
@@ -977,6 +983,9 @@ void __init detect_calgary(void)
 	if (swiotlb || no_iommu || iommu_detected)
 		return;
 
+	if (!use_calgary)
+		return;
+
 	if (!early_pci_allowed())
 		return;
 
diff -r cfdb02b1450e arch/x86_64/kernel/pci-dma.c
--- a/arch/x86_64/kernel/pci-dma.c	Sun Oct 29 09:25:34 2006 +0200
+++ b/arch/x86_64/kernel/pci-dma.c	Sun Oct 29 10:55:00 2006 +0200
@@ -296,6 +296,11 @@ __init int iommu_setup(char *p)
 		gart_parse_options(p);
 #endif
 
+#ifdef CONFIG_CALGARY_IOMMU
+		if (!strncmp(p, "calgary", 7))
+			use_calgary = 1;
+#endif /* CONFIG_CALGARY_IOMMU */
+
 		p += strcspn(p, ",");
 		if (*p == ',')
 			++p;
diff -r cfdb02b1450e include/asm-x86_64/calgary.h
--- a/include/asm-x86_64/calgary.h	Sun Oct 29 09:25:34 2006 +0200
+++ b/include/asm-x86_64/calgary.h	Sun Oct 29 10:55:00 2006 +0200
@@ -51,6 +51,8 @@ struct iommu_table {
 #define TCE_TABLE_SIZE_4M		6
 #define TCE_TABLE_SIZE_8M		7
 
+extern int use_calgary;
+
 #ifdef CONFIG_CALGARY_IOMMU
 extern int calgary_iommu_init(void);
 extern void detect_calgary(void);