[PATCH] Calgary: allow compiling Calgary in but not using it by default

This patch makes it possible to compile Calgary in but not use it by
default. In this mode, use 'iommu=calgary' to activate it.
Signed-off-by: NMuli Ben-Yehuda <muli@il.ibm.com>
Signed-off-by: NJon Mason <jdmason@kudzu.us>
Signed-off-by: NAndi Kleen <ak@suse.de>

Documentation/x86_64/boot-options.txt

@@ -179,7 +179,7 @@ PCI
 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
@@ -200,6 +200,7 @@ IOMMU
 	    buffering.
    nodac    Forbid DMA >4GB
    panic    Always panic when IOMMU overflows
+   calgary  Use the Calgary IOMMU if it is available
 
   swiotlb=pages[,force]
 

arch/x86_64/Kconfig

@@ -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

arch/x86_64/kernel/pci-calgary.c

@@ -43,6 +43,12 @@
 #include <asm/dma.h>
 #include <asm/rio.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 \
 	(PCI_VENDOR_ID_IBM | PCI_DEVICE_ID_IBM_CALGARY << 16)
@@ -1061,6 +1067,9 @@ void __init detect_calgary(void)
 	if (swiotlb || no_iommu || iommu_detected)
 		return;
 
+	if (!use_calgary)
+		return;
+
 	if (!early_pci_allowed())
 		return;
 

arch/x86_64/kernel/pci-dma.c

@@ -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;

include/asm-x86_64/calgary.h

@@ -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);