arch/openrisc/kernel/dma.c

   1 /*
   2  * OpenRISC Linux
   3  *
   4  * Linux architectural port borrowing liberally from similar works of
   5  * others.  All original copyrights apply as per the original source
   6  * declaration.
   7  *
   8  * Modifications for the OpenRISC architecture:
   9  * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
  10  * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
  11  *
  12  *      This program is free software; you can redistribute it and/or
  13  *      modify it under the terms of the GNU General Public License
  14  *      as published by the Free Software Foundation; either version
  15  *      2 of the License, or (at your option) any later version.
  16  *
  17  * DMA mapping callbacks...
  18  * As alloc_coherent is the only DMA callback being used currently, that's
  19  * the only thing implemented properly.  The rest need looking into...
  20  */
  21
  22 #include <linux/dma-noncoherent.h>
  23
  24 #include <asm/cpuinfo.h>
  25 #include <asm/spr_defs.h>
  26 #include <asm/tlbflush.h>
  27
  28 static int
  29 page_set_nocache(pte_t *pte, unsigned long addr,
  30                  unsigned long next, struct mm_walk *walk)
  31 {
  32         unsigned long cl;
  33         struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[smp_processor_id()];
  34
  35         pte_val(*pte) |= _PAGE_CI;
  36
  37         /*
  38          * Flush the page out of the TLB so that the new page flags get
  39          * picked up next time there's an access
  40          */
  41         flush_tlb_page(NULL, addr);
  42
  43         /* Flush page out of dcache */
  44         for (cl = __pa(addr); cl < __pa(next); cl += cpuinfo->dcache_block_size)
  45                 mtspr(SPR_DCBFR, cl);
  46
  47         return 0;
  48 }
  49
  50 static int
  51 page_clear_nocache(pte_t *pte, unsigned long addr,
  52                    unsigned long next, struct mm_walk *walk)
  53 {
  54         pte_val(*pte) &= ~_PAGE_CI;
  55
  56         /*
  57          * Flush the page out of the TLB so that the new page flags get
  58          * picked up next time there's an access
  59          */
  60         flush_tlb_page(NULL, addr);
  61
  62         return 0;
  63 }
  64
  65 /*
  66  * Alloc "coherent" memory, which for OpenRISC means simply uncached.
  67  *
  68  * This function effectively just calls __get_free_pages, sets the
  69  * cache-inhibit bit on those pages, and makes sure that the pages are
  70  * flushed out of the cache before they are used.
  71  *
  72  * If the NON_CONSISTENT attribute is set, then this function just
  73  * returns "normal", cachable memory.
  74  *
  75  * There are additional flags WEAK_ORDERING and WRITE_COMBINE to take
  76  * into consideration here, too.  All current known implementations of
  77  * the OR1K support only strongly ordered memory accesses, so that flag
  78  * is being ignored for now; uncached but write-combined memory is a
  79  * missing feature of the OR1K.
  80  */
  81 void *
  82 arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
  83                 gfp_t gfp, unsigned long attrs)
  84 {
  85         unsigned long va;
  86         void *page;
  87         struct mm_walk walk = {
  88                 .pte_entry = page_set_nocache,
  89                 .mm = &init_mm
  90         };
  91
  92         page = alloc_pages_exact(size, gfp | __GFP_ZERO);
  93         if (!page)
  94                 return NULL;
  95
  96         /* This gives us the real physical address of the first page. */
  97         *dma_handle = __pa(page);
  98
  99         va = (unsigned long)page;
 100
 101         if ((attrs & DMA_ATTR_NON_CONSISTENT) == 0) {
 102                 /*
 103                  * We need to iterate through the pages, clearing the dcache for
 104                  * them and setting the cache-inhibit bit.
 105                  */
 106                 if (walk_page_range(va, va + size, &walk)) {
 107                         free_pages_exact(page, size);
 108                         return NULL;
 109                 }
 110         }
 111
 112         return (void *)va;
 113 }
 114
 115 void
 116 arch_dma_free(struct device *dev, size_t size, void *vaddr,
 117                 dma_addr_t dma_handle, unsigned long attrs)
 118 {
 119         unsigned long va = (unsigned long)vaddr;
 120         struct mm_walk walk = {
 121                 .pte_entry = page_clear_nocache,
 122                 .mm = &init_mm
 123         };
 124
 125         if ((attrs & DMA_ATTR_NON_CONSISTENT) == 0) {
 126                 /* walk_page_range shouldn't be able to fail here */
 127                 WARN_ON(walk_page_range(va, va + size, &walk));
 128         }
 129
 130         free_pages_exact(vaddr, size);
 131 }
 132
 133 void arch_sync_dma_for_device(struct device *dev, phys_addr_t addr, size_t size,
 134                 enum dma_data_direction dir)
 135 {
 136         unsigned long cl;
 137         struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[smp_processor_id()];
 138
 139         switch (dir) {
 140         case DMA_TO_DEVICE:
 141                 /* Flush the dcache for the requested range */
 142                 for (cl = addr; cl < addr + size;
 143                      cl += cpuinfo->dcache_block_size)
 144                         mtspr(SPR_DCBFR, cl);
 145                 break;
 146         case DMA_FROM_DEVICE:
 147                 /* Invalidate the dcache for the requested range */
 148                 for (cl = addr; cl < addr + size;
 149                      cl += cpuinfo->dcache_block_size)
 150                         mtspr(SPR_DCBIR, cl);
 151                 break;
 152         default:
 153                 /*
 154                  * NOTE: If dir == DMA_BIDIRECTIONAL then there's no need to
 155                  * flush nor invalidate the cache here as the area will need
 156                  * to be manually synced anyway.
 157                  */
 158                 break;
 159         }
 160 }