From 905ecbf380607f84858bc6352bc1742830f367d8 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Sat, 15 May 2010 11:02:43 +0100
Subject: [PATCH] --- yaml --- r: 191752 b: refs/heads/master c:
 47ab0dee661dbd5aca67abe44a333e471134fbf9 h: refs/heads/master v: v3

---
 [refs]                               |  2 +-
 trunk/arch/arm/include/asm/pgtable.h |  2 +-
 trunk/arch/arm/include/asm/system.h  |  2 +-
 trunk/arch/arm/mm/Kconfig            | 19 +++++++++++++++++++
 4 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index af91d6cb88a7..be2fd6d8fe16 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 8c0b742ca7a7d21de0ddc87eda6ef0b282e4de18
+refs/heads/master: 47ab0dee661dbd5aca67abe44a333e471134fbf9
diff --git a/trunk/arch/arm/include/asm/pgtable.h b/trunk/arch/arm/include/asm/pgtable.h
index 11397687f42c..ab68cf1ef80f 100644
--- a/trunk/arch/arm/include/asm/pgtable.h
+++ b/trunk/arch/arm/include/asm/pgtable.h
@@ -314,7 +314,7 @@ static inline pte_t pte_mkspecial(pte_t pte) { return pte; }
 	__pgprot_modify(prot, L_PTE_MT_MASK, L_PTE_MT_UNCACHED)
 #define pgprot_writecombine(prot) \
 	__pgprot_modify(prot, L_PTE_MT_MASK, L_PTE_MT_BUFFERABLE)
-#if __LINUX_ARM_ARCH__ >= 7
+#ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE
 #define pgprot_dmacoherent(prot) \
 	__pgprot_modify(prot, L_PTE_MT_MASK|L_PTE_EXEC, L_PTE_MT_BUFFERABLE)
 #else
diff --git a/trunk/arch/arm/include/asm/system.h b/trunk/arch/arm/include/asm/system.h
index ca88e6a84707..02f5d99adbc0 100644
--- a/trunk/arch/arm/include/asm/system.h
+++ b/trunk/arch/arm/include/asm/system.h
@@ -137,7 +137,7 @@ extern unsigned int user_debug;
 #define dmb() __asm__ __volatile__ ("" : : : "memory")
 #endif
 
-#if __LINUX_ARM_ARCH__ >= 7 || defined(CONFIG_SMP)
+#if defined(CONFIG_ARM_DMA_MEM_BUFFERABLE) || defined(CONFIG_SMP)
 #define mb()		dmb()
 #define rmb()		dmb()
 #define wmb()		dmb()
diff --git a/trunk/arch/arm/mm/Kconfig b/trunk/arch/arm/mm/Kconfig
index c4ed9f93f646..573528d9c6d8 100644
--- a/trunk/arch/arm/mm/Kconfig
+++ b/trunk/arch/arm/mm/Kconfig
@@ -781,3 +781,22 @@ config ARM_L1_CACHE_SHIFT
 	int
 	default 6 if ARM_L1_CACHE_SHIFT_6
 	default 5
+
+config ARM_DMA_MEM_BUFFERABLE
+	bool "Use non-cacheable memory for DMA" if CPU_V6 && !CPU_V7
+	default y if CPU_V6 || CPU_V7
+	help
+	  Historically, the kernel has used strongly ordered mappings to
+	  provide DMA coherent memory.  With the advent of ARMv7, mapping
+	  memory with differing types results in unpredictable behaviour,
+	  so on these CPUs, this option is forced on.
+
+	  Multiple mappings with differing attributes is also unpredictable
+	  on ARMv6 CPUs, but since they do not have aggressive speculative
+	  prefetch, no harm appears to occur.
+
+	  However, drivers may be missing the necessary barriers for ARMv6,
+	  and therefore turning this on may result in unpredictable driver
+	  behaviour.  Therefore, we offer this as an option.
+
+	  You are recommended say 'Y' here and debug any affected drivers.