[PATCH] OpenRISC: DMA

[Jonas Bonn]

Simple DMA implementation.  Allows for allocation of coherent memory
(simply uncached) for DMA operations.

Signed-off-by: Jonas Bonn <jonas@xxxxxxxxxxxx>
---


 arch/openrisc/include/asm/dma-mapping.h |   62 +++++++++++++++
 arch/openrisc/kernel/dma.c              |  131
+++++++++++++++++++++++++++++++
 2 files changed, 193 insertions(+), 0 deletions(-)
 create mode 100644 arch/openrisc/include/asm/dma-mapping.h
 create mode 100644 arch/openrisc/kernel/dma.c

diff --git a/arch/openrisc/include/asm/dma-mapping.h
b/arch/openrisc/include/asm/dma-mapping.h
new file mode 100644
index 0000000..3d68ed8
--- /dev/null
+++ b/arch/openrisc/include/asm/dma-mapping.h
@@ -0,0 +1,62 @@
+/*
+ * OpenRISC Linux
+ *
+ * Linux architectural port borrowing liberally from similar works of
+ * others.  All original copyrights apply as per the original source
+ * declaration.
+ *
+ * OpenRISC implementation:
+ * Copyright (C) 2010-2011 Jonas Bonn <jonas@xxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef __ASM_OPENRISC_DMA_MAPPING_H
+#define __ASM_OPENRISC_DMA_MAPPING_H
+
+/*
+ * See Documentation/PCI/PCI-DMA-mapping.txt and
+ * Documentation/DMA-API.txt for documentation.
+ */
+
+#include <linux/dma-debug.h>
+#include <asm-generic/dma-coherent.h>
+
+#define DMA_ERROR_CODE		(~(dma_addr_t)0x0)
+
+int dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
+
+int dma_supported(struct device *dev, u64 mask);
+
+int dma_set_mask(struct device *dev, u64 mask);
+
+#define dma_alloc_noncoherent(d, s, h, f) dma_alloc_coherent(d, s, h,
f)
+#define dma_free_noncoherent(d, s, v, h) dma_free_coherent(d, s, v, h)
+
+void *or1k_dma_alloc_coherent(struct device *dev, size_t size,
+			      dma_addr_t *dma_handle, gfp_t flag);
+void or1k_dma_free_coherent(struct device *dev, size_t size, void
*vaddr,
+			    dma_addr_t dma_handle);
+
+static inline void *dma_alloc_coherent(struct device *dev, size_t size,
+					dma_addr_t *dma_handle, gfp_t flag)
+{
+	void *memory;
+
+	memory = or1k_dma_alloc_coherent(dev, size, dma_handle, flag);
+
+	debug_dma_alloc_coherent(dev, size, *dma_handle, memory);
+	return memory;
+}
+
+static inline void dma_free_coherent(struct device *dev, size_t size,
+				     void *cpu_addr, dma_addr_t dma_handle)
+{
+	debug_dma_free_coherent(dev, size, cpu_addr, dma_handle);
+	or1k_dma_free_coherent(dev, size, cpu_addr, dma_handle);
+}
+
+#endif	/* __ASM_OPENRISC_DMA_MAPPING_H */
diff --git a/arch/openrisc/kernel/dma.c b/arch/openrisc/kernel/dma.c
new file mode 100644
index 0000000..54d4773
--- /dev/null
+++ b/arch/openrisc/kernel/dma.c
@@ -0,0 +1,131 @@
+/*
+ * OpenRISC Linux
+ *
+ * Linux architectural port borrowing liberally from similar works of
+ * others.  All original copyrights apply as per the original source
+ * declaration.
+ *
+ * Modifications for the OpenRISC architecture:
+ * Copyright (C) 2003 Matjaz Breskvar <phoenix@xxxxxxxxx>
+ * Copyright (C) 2010-2011 Jonas Bonn <jonas@xxxxxxxxxxxx>
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ *
+ * DMA mapping callbacks...
+ * As alloc_coherent is the only DMA callback being used currently,
that's
+ * the only thing implemented properly.  The rest need looking into...
+ */
+
+#include <linux/device.h>
+#include <linux/dma-mapping.h>
+#include <linux/gfp.h>
+#include <linux/dma-debug.h>
+#include <linux/io.h>
+#include <linux/vmalloc.h>
+#include <linux/sched.h>
+
+#include <asm/cpuinfo.h>
+#include <asm/spr_defs.h>
+#include <asm/tlbflush.h>
+
+static int page_set_nocache(pte_t* pte, unsigned long addr,
+			    unsigned long next, struct mm_walk* walk)
+{
+	unsigned long cl;
+
+	pte_val(*pte) |= _PAGE_CI;
+
+	/*
+	 * Flush the page out of the TLB so that the new page flags get
+	 * picked up next time there's an access
+	 */
+	flush_tlb_page(NULL, addr);
+
+	/* Flush page out of dcache */
+	for (cl = __pa(addr); cl < __pa(next); cl +=
cpuinfo.dcache_block_size)
+		mtspr(SPR_DCBFR, cl);
+
+	return 0;
+}
+
+static int page_clear_nocache(pte_t* pte, unsigned long addr,
+			    unsigned long next, struct mm_walk* walk)
+{
+	pte_val(*pte) &= ~_PAGE_CI;
+
+	/*
+	 * Flush the page out of the TLB so that the new page flags get
+	 * picked up next time there's an access
+	 */
+	flush_tlb_page(NULL, addr);
+
+	return 0;
+}
+
+/*
+ * Alloc "coherent" memory, which for OpenRISC means simply uncached.
+ *
+ * This function effectively just calls __get_free_pages, sets the
+ * cache-inhibit bit on those pages, and makes sure that the pages are
+ * flushed out of the cache before they are used.
+ *
+ */
+void *or1k_dma_alloc_coherent(struct device *dev, size_t size,
+			      dma_addr_t *dma_handle, gfp_t gfp)
+{
+	unsigned long va;
+	void* page;
+	struct mm_walk walk = {
+		.pte_entry = page_set_nocache,
+		.mm = &init_mm
+	};
+
+	page = alloc_pages_exact(size, gfp);
+	if (!page)
+		return NULL;
+
+	/* This gives us the real physical address of the first page. */
+	*dma_handle = __pa(page);
+
+	va = (unsigned long) page;
+
+	/*
+	 * We need to iterate through the pages, clearing the dcache for
+	 * them and setting the cache-inhibit bit.
+	 */
+	if (walk_page_range(va, va+size, &walk)) {
+		free_pages_exact(page, size);
+		return NULL;
+	} 	
+
+	return (void*) va;
+}
+
+void or1k_dma_free_coherent(struct device *dev, size_t size, void
*vaddr,
+			    dma_addr_t dma_handle)
+{
+	unsigned long va = (unsigned long) vaddr;
+	struct mm_walk walk = {
+		.pte_entry = page_clear_nocache,
+		.mm = &init_mm
+	};
+
+	/* walk_page_range shouldn't be able to fail here */
+	WARN_ON(walk_page_range(va, va+size, &walk));
+
+	free_pages_exact(vaddr, size);
+}
+
+/* Number of entries preallocated for DMA-API debugging */
+#define PREALLOC_DMA_DEBUG_ENTRIES (1 << 16)
+
+static int __init dma_init(void)
+{
+	dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
+
+	return 0;
+}
+fs_initcall(dma_init);
-- 
1.7.1


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