dma-mapping: move dma_map_(un)single() to <linux/dma-mapping.h>

The implementation of dma_map_single() and dma_unmap_single() is
exactly the same for all the architectures that support them.

Factor them out to <linux/dma-mapping.h>, and make all drivers to
include <linux/dma-mapping.h> instead of <asm/dma-mapping.h>.

If we need to differentiate them for some architectures, we can
move the generic definitions to <asm-generic/dma-mapping.h>.

Add some comments to the helpers. The concept is quite similar to
the DMA-API of Linux kernel. Drivers are agnostic about what is
going on behind the scene. Just call dma_map_single() before the
DMA, and dma_unmap_single() after it.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
new file mode 100644
index 0000000..20b6d60
--- /dev/null
+++ b/include/linux/dma-mapping.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_DMA_MAPPING_H
+#define _LINUX_DMA_MAPPING_H
+
+#include <linux/dma-direction.h>
+#include <linux/types.h>
+#include <asm/dma-mapping.h>
+#include <cpu_func.h>
+
+#define dma_mapping_error(x, y)	0
+
+/**
+ * Map a buffer to make it available to the DMA device
+ *
+ * Linux-like DMA API that is intended to be used from drivers. This hides the
+ * underlying cache operation from drivers. Call this before starting the DMA
+ * transfer. In most of architectures in U-Boot, the virtual address matches to
+ * the physical address (but we have exceptions like sandbox). U-Boot does not
+ * support iommu at the driver level, so it also matches to the DMA address.
+ * Hence, this helper currently just performs the cache operation, then returns
+ * straight-mapped dma_address, which is intended to be set to the register of
+ * the DMA device.
+ *
+ * @vaddr: address of the buffer
+ * @len: length of the buffer
+ * @dir: the direction of DMA
+ */
+static inline dma_addr_t dma_map_single(void *vaddr, size_t len,
+					enum dma_data_direction dir)
+{
+	unsigned long addr = (unsigned long)vaddr;
+
+	len = ALIGN(len, ARCH_DMA_MINALIGN);
+
+	if (dir == DMA_FROM_DEVICE)
+		invalidate_dcache_range(addr, addr + len);
+	else
+		flush_dcache_range(addr, addr + len);
+
+	return addr;
+}
+
+/**
+ * Unmap a buffer to make it available to CPU
+ *
+ * Linux-like DMA API that is intended to be used from drivers. This hides the
+ * underlying cache operation from drivers. Call this after finishin the DMA
+ * transfer.
+ *
+ * @addr: DMA address
+ * @len: length of the buffer
+ * @dir: the direction of DMA
+ */
+static inline void dma_unmap_single(dma_addr_t addr, size_t len,
+				    enum dma_data_direction dir)
+{
+	len = ALIGN(len, ARCH_DMA_MINALIGN);
+
+	if (dir != DMA_TO_DEVICE)
+		invalidate_dcache_range(addr, addr + len);
+}
+
+#endif