MIPS: Sanitise coherentio semantics

The coherentio variable has previously been used as a boolean value,
indicating whether the user specified that coherent I/O should be
enabled or disabled. It failed to take into account the case where the
user does not specify any preference, in which case it makes sense that
we should default to coherent I/O if the hardware supports it
(hw_coherentio is non-zero).

Introduce an enum to clarify the 3 different values of coherentio & use
it throughout the code, modifying plat_device_is_coherent() &
r4k_cache_init() to take into account the default case.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Paul Burton <paul.burton@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/14347/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 18 insertions, 4 deletions

diff --git a/arch/mips/include/asm/dma-coherence.h b/arch/mips/include/asm/dma-coherence.h
index bc5e85d579e6..4fbce79fb57f 100644
--- a/arch/mips/include/asm/dma-coherence.h
+++ b/arch/mips/include/asm/dma-coherence.h
@@ -9,14 +9,20 @@
 #ifndef __ASM_DMA_COHERENCE_H
 #define __ASM_DMA_COHERENCE_H
 
+enum coherent_io_user_state {
+        IO_COHERENCE_DEFAULT,
+        IO_COHERENCE_ENABLED,
+        IO_COHERENCE_DISABLED,
+};
+
 #ifdef CONFIG_DMA_MAYBE_COHERENT
-extern int coherentio;
+extern enum coherent_io_user_state coherentio;
 extern int hw_coherentio;
 #else
 #ifdef CONFIG_DMA_COHERENT
-#define coherentio      1
+#define coherentio      IO_COHERENCE_ENABLED
 #else
-#define coherentio      0
+#define coherentio      IO_COHERENCE_DISABLED
 #endif
 #define hw_coherentio   0
 #endif /* CONFIG_DMA_MAYBE_COHERENT */
diff --git a/arch/mips/include/asm/mach-generic/dma-coherence.h b/arch/mips/include/asm/mach-generic/dma-coherence.h
index 0f8a354fd468..8484f82fc794 100644
--- a/arch/mips/include/asm/mach-generic/dma-coherence.h
+++ b/arch/mips/include/asm/mach-generic/dma-coherence.h
@@ -49,7 +49,15 @@ static inline int plat_dma_supported(struct device *dev, u64 mask)
 
 static inline int plat_device_is_coherent(struct device *dev)
 {
-        return coherentio;
+        switch (coherentio) {
+        default:
+        case IO_COHERENCE_DEFAULT:
+                return hw_coherentio;
+        case IO_COHERENCE_ENABLED:
+                return 1;
+        case IO_COHERENCE_DISABLED:
+                return 0;
+        }
 }
 
 #ifndef plat_post_dma_flush