arch/arc/mm/dma.c

   1 /*
   2  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 /*
  10  * DMA Coherent API Notes
  11  *
  12  * I/O is inherently non-coherent on ARC. So a coherent DMA buffer is
  13  * implemented by accessintg it using a kernel virtual address, with
  14  * Cache bit off in the TLB entry.
  15  *
  16  * The default DMA address == Phy address which is 0x8000_0000 based.
  17  */
  18
  19 #include <linux/dma-mapping.h>
  20 #include <linux/dma-debug.h>
  21 #include <linux/export.h>
  22 #include <asm/cacheflush.h>
  23
  24 /*
  25  * Helpers for Coherent DMA API.
  26  */
  27 void *dma_alloc_noncoherent(struct device *dev, size_t size,
  28                             dma_addr_t *dma_handle, gfp_t gfp)
  29 {
  30         void *paddr;
  31
  32         /* This is linear addr (0x8000_0000 based) */
  33         paddr = alloc_pages_exact(size, gfp);
  34         if (!paddr)
  35                 return NULL;
  36
  37         /* This is bus address, platform dependent */
  38         *dma_handle = (dma_addr_t)paddr;
  39
  40         return paddr;
  41 }
  42 EXPORT_SYMBOL(dma_alloc_noncoherent);
  43
  44 void dma_free_noncoherent(struct device *dev, size_t size, void *vaddr,
  45                           dma_addr_t dma_handle)
  46 {
  47         free_pages_exact((void *)dma_handle, size);
  48 }
  49 EXPORT_SYMBOL(dma_free_noncoherent);
  50
  51 void *dma_alloc_coherent(struct device *dev, size_t size,
  52                          dma_addr_t *dma_handle, gfp_t gfp)
  53 {
  54         void *paddr, *kvaddr;
  55
  56         /* This is linear addr (0x8000_0000 based) */
  57         paddr = alloc_pages_exact(size, gfp);
  58         if (!paddr)
  59                 return NULL;
  60
  61         /* This is kernel Virtual address (0x7000_0000 based) */
  62         kvaddr = ioremap_nocache((unsigned long)paddr, size);
  63         if (kvaddr == NULL)
  64                 return NULL;
  65
  66         /* This is bus address, platform dependent */
  67         *dma_handle = (dma_addr_t)paddr;
  68
  69         /*
  70          * Evict any existing L1 and/or L2 lines for the backing page
  71          * in case it was used earlier as a normal "cached" page.
  72          * Yeah this bit us - STAR 9000898266
  73          *
  74          * Although core does call flush_cache_vmap(), it gets kvaddr hence
  75          * can't be used to efficiently flush L1 and/or L2 which need paddr
  76          * Currently flush_cache_vmap nukes the L1 cache completely which
  77          * will be optimized as a separate commit
  78          */
  79         dma_cache_wback_inv((unsigned long)paddr, size);
  80
  81         return kvaddr;
  82 }
  83 EXPORT_SYMBOL(dma_alloc_coherent);
  84
  85 void dma_free_coherent(struct device *dev, size_t size, void *kvaddr,
  86                        dma_addr_t dma_handle)
  87 {
  88         iounmap((void __force __iomem *)kvaddr);
  89
  90         free_pages_exact((void *)dma_handle, size);
  91 }
  92 EXPORT_SYMBOL(dma_free_coherent);
  93
  94 /*
  95  * Helper for streaming DMA...
  96  */
  97 void __arc_dma_cache_sync(unsigned long paddr, size_t size,
  98                           enum dma_data_direction dir)
  99 {
 100         __inline_dma_cache_sync(paddr, size, dir);
 101 }
 102 EXPORT_SYMBOL(__arc_dma_cache_sync);