From: George Beshers <gbeshers@redhat.com>
Date: Thu, 3 Dec 2009 15:10:58 -0500
Subject: [ia64] dma_get_required_mask altix workaround
Message-id: <4B17D502.8040003@redhat.com>
Patchwork-id: 21665
O-Subject: [RHEL5.5 PATCH] dma_get_required_mask altix workaround
Bugzilla: 517192
RH-Acked-by: Prarit Bhargava <prarit@redhat.com>

BZ#517192

A direct back port of the upstream patch,

  http://www.kernel.org/hg/index.cgi/linux-2.6/rev/8a0cc70eb319
  commit 175add1981e53d22caba8f42d5f924a4de507b6c

is unacceptable as it breaks kabi, but the patch log comment
is still accurate:

  [IA64] SN specific version of dma_get_required_mask()

  Create a platform specific version of dma_get_required_mask()
  for ia64 SN Altix. All SN Altix platforms support 64 bit DMA
  addressing regardless of the size of system memory.
  Create an ia64 machvec for dma_get_required_mask, with the
  SN version unconditionally returning DMA_64BIT_MASK.

  Signed-off-by: John Keller <jpk@sgi.com>
  Signed-off-by: Tony Luck <tony.luck@intel.com>

The attached patch is a bit of a hack, but is short and gets the
job done; Prarit and Don confirmed my observation that avoiding
kabi breakage caused things to stray too far from the original
patch.

The whitespace oversight has been addressed.

Please ack.

George

Signed-off-by: Don Zickus <dzickus@redhat.com>

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index e90c4e1..8c0b947 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -544,9 +544,17 @@ int __init platform_bus_init(void)
 #ifndef ARCH_HAS_DMA_GET_REQUIRED_MASK
 u64 dma_get_required_mask(struct device *dev)
 {
-	u32 low_totalram = ((max_pfn - 1) << PAGE_SHIFT);
-	u32 high_totalram = ((max_pfn - 1) >> (32 - PAGE_SHIFT));
 	u64 mask;
+	u32 low_totalram;
+	u32 high_totalram;
+
+#ifdef CONFIG_IA64
+	if (ia64_platform_is("sn2"))
+		return DMA_64BIT_MASK;
+#endif /* CONFIG_IA64 */
+
+	low_totalram = ((max_pfn - 1) << PAGE_SHIFT);
+	high_totalram = ((max_pfn - 1) >> (32 - PAGE_SHIFT));
 
 	if (!high_totalram) {
 		/* convert to mask just covering totalram */