C6X: memory management and DMA support

Original port to early 2.6 kernel using TI COFF toolchain.
Brought up to date by Mark Salter <msalter@redhat.com>

The C6X architecture currently lacks an MMU so memory management is relatively
simple. There is no bus snooping between L2 and main memory but coherent DMA
memory is supported by making regions of main memory uncached. If such a region
is desired, it can be specified on the commandline with a "memdma=" argument.

Signed-off-by: Aurelien Jacquiot <a-jacquiot@ti.com>
Signed-off-by: Mark Salter <msalter@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 143 insertions, 0 deletions

diff --git a/arch/c6x/mm/dma-coherent.c b/arch/c6x/mm/dma-coherent.c
new file mode 100644
index 000000000000..4187e5180373
--- /dev/null
+++ b/arch/c6x/mm/dma-coherent.c
@@ -0,0 +1,143 @@
+/*
+ *  Port on Texas Instruments TMS320C6x architecture
+ *
+ *  Copyright (C) 2004, 2009, 2010, 2011 Texas Instruments Incorporated
+ *  Author: Aurelien Jacquiot <aurelien.jacquiot@ti.com>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
+ *
+ *  DMA uncached mapping support.
+ *
+ *  Using code pulled from ARM
+ *  Copyright (C) 2000-2004 Russell King
+ *
+ */
+#include <linux/slab.h>
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/dma-mapping.h>
+#include <linux/memblock.h>
+
+#include <asm/page.h>
+
+/*
+ * DMA coherent memory management, can be redefined using the memdma=
+ * kernel command line
+ */
+
+/* none by default */
+static phys_addr_t dma_base;
+static u32 dma_size;
+static u32 dma_pages;
+
+static unsigned long *dma_bitmap;
+
+/* bitmap lock */
+static DEFINE_SPINLOCK(dma_lock);
+
+/*
+ * Return a DMA coherent and contiguous memory chunk from the DMA memory
+ */
+static inline u32 __alloc_dma_pages(int order)
+{
+        unsigned long flags;
+        u32 pos;
+
+        spin_lock_irqsave(&dma_lock, flags);
+        pos = bitmap_find_free_region(dma_bitmap, dma_pages, order);
+        spin_unlock_irqrestore(&dma_lock, flags);
+
+        return dma_base + (pos << PAGE_SHIFT);
+}
+
+static void __free_dma_pages(u32 addr, int order)
+{
+        unsigned long flags;
+        u32 pos = (addr - dma_base) >> PAGE_SHIFT;
+
+        if (addr < dma_base || (pos + (1 << order)) >= dma_pages) {
+                printk(KERN_ERR "%s: freeing outside range.\n", __func__);
+                BUG();
+        }
+
+        spin_lock_irqsave(&dma_lock, flags);
+        bitmap_release_region(dma_bitmap, pos, order);
+        spin_unlock_irqrestore(&dma_lock, flags);
+}
+
+/*
+ * Allocate DMA coherent memory space and return both the kernel
+ * virtual and DMA address for that space.
+ */
+void *dma_alloc_coherent(struct device *dev, size_t size,
+                         dma_addr_t *handle, gfp_t gfp)
+{
+        u32 paddr;
+        int order;
+
+        if (!dma_size || !size)
+                return NULL;
+
+        order = get_count_order(((size - 1) >> PAGE_SHIFT) + 1);
+
+        paddr = __alloc_dma_pages(order);
+
+        if (handle)
+                *handle = paddr;
+
+        if (!paddr)
+                return NULL;
+
+        return phys_to_virt(paddr);
+}
+EXPORT_SYMBOL(dma_alloc_coherent);
+
+/*
+ * Free DMA coherent memory as defined by the above mapping.
+ */
+void dma_free_coherent(struct device *dev, size_t size, void *vaddr,
+                       dma_addr_t dma_handle)
+{
+        int order;
+
+        if (!dma_size || !size)
+                return;
+
+        order = get_count_order(((size - 1) >> PAGE_SHIFT) + 1);
+
+        __free_dma_pages(virt_to_phys(vaddr), order);
+}
+EXPORT_SYMBOL(dma_free_coherent);
+
+/*
+ * Initialise the coherent DMA memory allocator using the given uncached region.
+ */
+void __init coherent_mem_init(phys_addr_t start, u32 size)
+{
+        phys_addr_t bitmap_phys;
+
+        if (!size)
+                return;
+
+        printk(KERN_INFO
+               "Coherent memory (DMA) region start=0x%x size=0x%x\n",
+               start, size);
+
+        dma_base = start;
+        dma_size = size;
+
+        /* allocate bitmap */
+        dma_pages = dma_size >> PAGE_SHIFT;
+        if (dma_size & (PAGE_SIZE - 1))
+                ++dma_pages;
+
+        bitmap_phys = memblock_alloc(BITS_TO_LONGS(dma_pages) * sizeof(long),
+                                     sizeof(long));
+
+        dma_bitmap = phys_to_virt(bitmap_phys);
+        memset(dma_bitmap, 0, dma_pages * PAGE_SIZE);
+}