MIPS: Add option to disable software I/O coherency.

Some MIPS controllers have hardware I/O coherency. This patch
detects those and turns off software coherency. A new kernel
command line option also allows the user to manually turn
software coherency on or off.

Signed-off-by: Steven J. Hill <Steven.Hill@imgtec.com>

3 files changed, 18 insertions, 3 deletions

diff --git a/arch/mips/include/asm/dma-coherence.h b/arch/mips/include/asm/dma-coherence.h
new file mode 100644
index 0000000..242cbb3
--- /dev/null
+++ b/arch/mips/include/asm/dma-coherence.h
@@ -0,0 +1,15 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2006  Ralf Baechle <ralf@linux-mips.org>
+ *
+ */
+#ifndef __ASM_DMA_COHERENCE_H
+#define __ASM_DMA_COHERENCE_H
+
+extern int coherentio;
+extern int hw_coherentio;
+
+#endif
diff --git a/arch/mips/include/asm/dma-mapping.h b/arch/mips/include/asm/dma-mapping.h
index f8fc74b..84238c5 100644
--- a/arch/mips/include/asm/dma-mapping.h
+++ b/arch/mips/include/asm/dma-mapping.h
@@ -2,6 +2,7 @@
 #define _ASM_DMA_MAPPING_H
 
 #include <asm/scatterlist.h>
+#include <asm/dma-coherence.h>
 #include <asm/cache.h>
 #include <asm-generic/dma-coherent.h>
 
diff --git a/arch/mips/include/asm/mach-generic/dma-coherence.h b/arch/mips/include/asm/mach-generic/dma-coherence.h
index 9c95177..fe23034 100644
--- a/arch/mips/include/asm/mach-generic/dma-coherence.h
+++ b/arch/mips/include/asm/mach-generic/dma-coherence.h
@@ -61,9 +61,8 @@ static inline int plat_device_is_coherent(struct device *dev)
 {
 #ifdef CONFIG_DMA_COHERENT
 	return 1;
-#endif
-#ifdef CONFIG_DMA_NONCOHERENT
-	return 0;
+#else
+	return coherentio;
 #endif
 }