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>

1 files changed, 27 insertions, 6 deletions

diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index a5bc528d4328..c7a72faeb146 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();
+        }
+}