[RFC PATCH] powerpc: add ioremap_wt

[Michael Moese <michael.moese@men.de>]

Allow for IO memory to be mapped cacheable for performing
PCI read bursts.

Signed-off-by: Michael Moese <michael.moese@men.de>
---
 arch/powerpc/include/asm/io.h | 3 +++
 arch/powerpc/mm/pgtable_32.c  | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/arch/powerpc/include/asm/io.h b/arch/powerpc/include/asm/io.h
index 45698d5..9591fff 100644
--- a/arch/powerpc/include/asm/io.h
+++ b/arch/powerpc/include/asm/io.h
@@ -631,6 +631,8 @@ static inline void iosync(void)
  *
  * * ioremap_wc enables write combining
  *
+ * * ioremap_wc enables write thru
+ *
  * * iounmap undoes such a mapping and can be hooked
  *
  * * __ioremap_at (and the pending __iounmap_at) are low level functions to
@@ -652,6 +654,7 @@ extern void __iomem *ioremap(phys_addr_t address, unsigned long size);
 extern void __iomem *ioremap_prot(phys_addr_t address, unsigned long size,
 				  unsigned long flags);
 extern void __iomem *ioremap_wc(phys_addr_t address, unsigned long size);
+extern void __iomem *ioremap_wt(phys_addr_t address, unsigned long size);
 #define ioremap_nocache(addr, size)	ioremap((addr), (size))
 
 extern void iounmap(volatile void __iomem *addr);
diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index 51f8795..9ab0a54 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -141,6 +141,14 @@ ioremap_wc(phys_addr_t addr, unsigned long size)
 EXPORT_SYMBOL(ioremap_wc);
 
 void __iomem *
+ioremap_wt(phys_addr_t addr, unsigned long size)
+{
+	return __ioremap_caller(addr, size, _PAGE_WRITETHRU,
+				__builtin_return_address(0));
+}
+EXPORT_SYMBOL(ioremap_wt);
+
+void __iomem *
 ioremap_prot(phys_addr_t addr, unsigned long size, unsigned long flags)
 {
 	/* writeable implies dirty for kernel addresses */
-- 
1.8.5.3