linux-kernel - [PATCH] m32r: add simple dma

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Date:   Sat,  8 Oct 2016 23:23:18 +0530
From:   Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        fengguang.wu@...el.com
Subject: [PATCH] m32r: add simple dma

Some builds of m32r were failing as it tried to build few drivers which
needed dma but m32r is not having dma support. Objections were raised
when it was tried to make those drivers depend on HAS_DMA. So the next
best thing is to add dma support to m32r.
dma_noop is a very simple dma with 1:1 memory mapping.

Signed-off-by: Sudip Mukherjee <sudip.mukherjee@...ethink.co.uk>
---

Hi Andrew,
Just to let you know that this was not tested on any board. I think I
have told you earlier that inspite of all  my efforts I could not find
 any source of information to procure a board of m32r.

Hi Fengguang,
If Andrew accepts this patch then it will open pandora's box as lots of
other drivers which were never build for m32r will be built now and you
are going to gets lots and lots of new build warnings. But nothing
breaks.

 arch/m32r/Kconfig                   |  2 +-
 arch/m32r/include/asm/device.h      |  6 +++++-
 arch/m32r/include/asm/dma-mapping.h | 32 ++++++++++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 arch/m32r/include/asm/dma-mapping.h

diff --git a/arch/m32r/Kconfig b/arch/m32r/Kconfig
index 3cc8498..d227a69 100644
--- a/arch/m32r/Kconfig
+++ b/arch/m32r/Kconfig
@@ -34,7 +34,7 @@ config NO_IOPORT_MAP
 	def_bool y
 
 config NO_DMA
-	def_bool y
+	def_bool n
 
 config HZ
 	int
diff --git a/arch/m32r/include/asm/device.h b/arch/m32r/include/asm/device.h
index d8f9872..4a9f35e 100644
--- a/arch/m32r/include/asm/device.h
+++ b/arch/m32r/include/asm/device.h
@@ -3,5 +3,9 @@
  *
  * This file is released under the GPLv2
  */
-#include <asm-generic/device.h>
+struct dev_archdata {
+	struct dma_map_ops *dma_ops;
+};
 
+struct pdev_archdata {
+};
diff --git a/arch/m32r/include/asm/dma-mapping.h b/arch/m32r/include/asm/dma-mapping.h
new file mode 100644
index 0000000..1666ca6
--- /dev/null
+++ b/arch/m32r/include/asm/dma-mapping.h
@@ -0,0 +1,32 @@
+#ifndef _ASM_M32R_DMA_MAPPING_H
+#define _ASM_M32R_DMA_MAPPING_H
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/scatterlist.h>
+#include <linux/dma-debug.h>
+#include <linux/io.h>
+
+#define DMA_ERROR_CODE (~(dma_addr_t)0x0)
+
+static inline struct dma_map_ops *get_dma_ops(struct device *dev)
+{
+	if (dev && dev->archdata.dma_ops)
+		return dev->archdata.dma_ops;
+	return &dma_noop_ops;
+}
+
+static inline void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
+				  enum dma_data_direction direction)
+{
+}
+
+static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
+{
+	if (!dev->dma_mask)
+		return false;
+	return addr + size - 1 <= *dev->dma_mask;
+}
+
+#endif /* _ASM_M32R_DMA_MAPPING_H */
-- 
1.9.1