[PATCH 1/2] mmu: define MAP_WRITECOMBINE for all architectures

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Write Combine (WC) memory is an optimization over uncached memory,
especially suitable for framebuffers. We allocate WC memory using
dma_alloc_writecombine(), but it can be useful to remap existing memory
not allocated within barebox as WC.

To allow this, let's define MAP_WRITECOMBINE globally with a fallback to
MAP_UNCACHED if not available.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 arch/Kconfig              |  3 +++
 arch/arm/Kconfig          |  1 +
 arch/arm/cpu/mmu-common.h |  1 -
 arch/arm/cpu/mmu_32.c     |  6 +++---
 arch/arm/cpu/mmu_64.c     |  4 ++--
 include/mmu.h             | 14 ++++++++++----
 6 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 919c8cfebab5..55618bf896c2 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -59,6 +59,9 @@ config ARCH_HAS_CTRLC
 config ARCH_DMA_DEFAULT_COHERENT
 	bool
 
+config ARCH_HAS_DMA_WRITE_COMBINE
+	bool
+
 config ARCH_HAS_ASAN_FIBER_API
 	bool
 
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 7a3952700aa8..9694cb5b7463 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -16,6 +16,7 @@ config ARM
 	select HAVE_ARCH_BOARD_GENERIC_DT if OFDEVICE
 	select HAVE_ARCH_BOOTM_OFTREE
 	select HW_HAS_PCI
+	select ARCH_HAS_DMA_WRITE_COMBINE
 	default y
 
 config ARCH_LINUX_NAME
diff --git a/arch/arm/cpu/mmu-common.h b/arch/arm/cpu/mmu-common.h
index ac11a87be416..3bca5cc3b821 100644
--- a/arch/arm/cpu/mmu-common.h
+++ b/arch/arm/cpu/mmu-common.h
@@ -10,7 +10,6 @@
 #include <linux/kernel.h>
 #include <linux/sizes.h>
 
-#define ARCH_MAP_WRITECOMBINE	((unsigned)-1)
 #define ARCH_MAP_CACHED_RWX	((unsigned)-2)
 #define ARCH_MAP_CACHED_RO	((unsigned)-3)
 
diff --git a/arch/arm/cpu/mmu_32.c b/arch/arm/cpu/mmu_32.c
index 67f1fe59886a..89a18d342b80 100644
--- a/arch/arm/cpu/mmu_32.c
+++ b/arch/arm/cpu/mmu_32.c
@@ -238,7 +238,7 @@ static uint32_t get_pte_flags(int map_type)
 			return PTE_FLAGS_UNCACHED_V7;
 		case MAP_CODE:
 			return PTE_FLAGS_CODE_V7;
-		case ARCH_MAP_WRITECOMBINE:
+		case MAP_WRITECOMBINE:
 			return PTE_FLAGS_WC_V7;
 		case MAP_FAULT:
 		default:
@@ -253,7 +253,7 @@ static uint32_t get_pte_flags(int map_type)
 		case MAP_CACHED:
 			return PTE_FLAGS_CACHED_V4;
 		case MAP_UNCACHED:
-		case ARCH_MAP_WRITECOMBINE:
+		case MAP_WRITECOMBINE:
 			return PTE_FLAGS_UNCACHED_V4;
 		case MAP_FAULT:
 		default:
@@ -651,7 +651,7 @@ void mmu_disable(void)
 
 void *dma_alloc_writecombine(struct device *dev, size_t size, dma_addr_t *dma_handle)
 {
-	return dma_alloc_map(dev, size, dma_handle, ARCH_MAP_WRITECOMBINE);
+	return dma_alloc_map(dev, size, dma_handle, MAP_WRITECOMBINE);
 }
 
 void mmu_early_enable(unsigned long membase, unsigned long memsize, unsigned long barebox_start)
diff --git a/arch/arm/cpu/mmu_64.c b/arch/arm/cpu/mmu_64.c
index abcc970f4bff..a229e4cb5526 100644
--- a/arch/arm/cpu/mmu_64.c
+++ b/arch/arm/cpu/mmu_64.c
@@ -295,7 +295,7 @@ static unsigned long get_pte_attrs(unsigned flags)
 		return attrs_xn() | UNCACHED_MEM;
 	case MAP_FAULT:
 		return 0x0;
-	case ARCH_MAP_WRITECOMBINE:
+	case MAP_WRITECOMBINE:
 		return attrs_xn() | MEM_ALLOC_WRITECOMBINE;
 	case MAP_CODE:
 		return CACHED_MEM | PTE_BLOCK_RO;
@@ -448,7 +448,7 @@ void dma_flush_range(void *ptr, size_t size)
 
 void *dma_alloc_writecombine(struct device *dev, size_t size, dma_addr_t *dma_handle)
 {
-	return dma_alloc_map(dev, size, dma_handle, ARCH_MAP_WRITECOMBINE);
+	return dma_alloc_map(dev, size, dma_handle, MAP_WRITECOMBINE);
 }
 
 static void init_range(size_t total_level0_tables)
diff --git a/include/mmu.h b/include/mmu.h
index 20855e89eda3..17c04d2fa05f 100644
--- a/include/mmu.h
+++ b/include/mmu.h
@@ -5,10 +5,16 @@
 #include <linux/types.h>
 #include <errno.h>
 
-#define MAP_UNCACHED	0
-#define MAP_CACHED	1
-#define MAP_FAULT	2
-#define MAP_CODE	3
+#define MAP_UNCACHED		0
+#define MAP_CACHED		1
+#define MAP_FAULT		2
+#define MAP_CODE		3
+
+#ifdef CONFIG_ARCH_HAS_DMA_WRITE_COMBINE
+#define MAP_WRITECOMBINE	4
+#else
+#define MAP_WRITECOMBINE	MAP_UNCACHED
+#endif
 
 /*
  * Depending on the architecture the default mapping can be
-- 
2.39.5