x86, swiotlb: Simplify SWIOTLB pci_swiotlb_detect routine.

In 'pci_swiotlb_detect' we used to do two different things:
 a). If user provided 'iommu=soft' or 'swiotlb=force' we
     would set swiotlb=1 and return 1 (and forcing pci-dma.c
     to call pci_swiotlb_init() immediately).
 b). If 4GB or more would be detected and if user did not specify
     iommu=off, we would set 'swiotlb=1' and return whatever 'a)'
     figured out.

We simplify this by splitting a) and b) in two different routines.

CC: Fujita Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
LKML-Reference: <1282845485-8991-5-git-send-email-konrad.wilk@oracle.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

2 files changed, 30 insertions, 7 deletions

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 9f07cfc..1b3beb5 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -133,9 +133,11 @@ void __init pci_iommu_alloc(void)
 	/* free the range so iommu could get some range less than 4G */
 	dma32_free_bootmem();
 
-	if (pci_xen_swiotlb_detect() || pci_swiotlb_detect())
+	if (pci_xen_swiotlb_detect() || pci_swiotlb_detect_override())
 		goto out;
 
+	pci_swiotlb_detect_4gb();
+
 	gart_iommu_hole_init();
 
 	detect_calgary();
diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index a5bc528..c7a72fa 100644
--- a/arch/x86/kernel/pci-swiotlb.c
+++ b/arch/x86/kernel/pci-swiotlb.c
@@ -41,24 +41,33 @@ static struct dma_map_ops swiotlb_dma_ops = {
 };
 
 /*
- * pci_swiotlb_detect - set swiotlb to 1 if necessary
+ * pci_swiotlb_detect_override - set swiotlb to 1 if necessary
  *
  * This returns non-zero if we are forced to use swiotlb (by the boot
  * option).
  */
-int __init pci_swiotlb_detect(void)
+int __init pci_swiotlb_detect_override(void)
 {
 	int use_swiotlb = swiotlb | swiotlb_force;
 
+	if (swiotlb_force)
+		swiotlb = 1;
+
+	return use_swiotlb;
+}
+
+/*
+ * if 4GB or more detected (and iommu=off not set) return 1
+ * and set swiotlb to 1.
+ */
+int __init pci_swiotlb_detect_4gb(void)
+{
 	/* don't initialize swiotlb if iommu=off (no_iommu=1) */
 #ifdef CONFIG_X86_64
 	if (!no_iommu && max_pfn > MAX_DMA32_PFN)
 		swiotlb = 1;
 #endif
-	if (swiotlb_force)
-		swiotlb = 1;
-
-	return use_swiotlb;
+	return swiotlb;
 }
 
 void __init pci_swiotlb_init(void)
@@ -68,3 +77,15 @@ void __init pci_swiotlb_init(void)
 		dma_ops = &swiotlb_dma_ops;
 	}
 }
+
+void __init pci_swiotlb_late_init(void)
+{
+	/* An IOMMU turned us off. */
+	if (!swiotlb)
+		swiotlb_free();
+	else {
+		printk(KERN_INFO "PCI-DMA: "
+		       "Using software bounce buffering for IO (SWIOTLB)\n");
+		swiotlb_print_info();
+	}
+}