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dma-noncoherent.c

/*
 *  PowerPC version derived from arch/arm/mm/consistent.c
 *    Copyright (C) 2001 Dan Malek (dmalek@jlc.net)
 *
 *  Copyright (C) 2000 Russell King
 *
 * Consistent memory allocators.  Used for DMA devices that want to
 * share uncached memory with the processor core.  The function return
 * is the virtual address and 'dma_handle' is the physical address.
 * Mostly stolen from the ARM port, with some changes for PowerPC.
 *                                  -- Dan
 *
 * Reorganized to get rid of the arch-specific consistent_* functions
 * and provide non-coherent implementations for the DMA API. -Matt
 *
 * Added in_interrupt() safe dma_alloc_coherent()/dma_free_coherent()
 * implementation. This is pulled straight from ARM and barely
 * modified. -Matt
 *
 * 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.
 */

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/highmem.h>
#include <linux/dma-mapping.h>

#include <asm/tlbflush.h>

/*
 * This address range defaults to a value that is safe for all
 * platforms which currently set CONFIG_NOT_COHERENT_CACHE. It
 * can be further configured for specific applications under
 * the "Advanced Setup" menu. -Matt
 */
#define CONSISTENT_BASE (CONFIG_CONSISTENT_START)
#define CONSISTENT_END  (CONFIG_CONSISTENT_START + CONFIG_CONSISTENT_SIZE)
#define CONSISTENT_OFFSET(x)  (((unsigned long)(x) - CONSISTENT_BASE) >> PAGE_SHIFT)

/*
 * This is the page table (2MB) covering uncached, DMA consistent allocations
 */
static pte_t *consistent_pte;
static DEFINE_SPINLOCK(consistent_lock);

/*
 * VM region handling support.
 *
 * This should become something generic, handling VM region allocations for
 * vmalloc and similar (ioremap, module space, etc).
 *
 * I envisage vmalloc()'s supporting vm_struct becoming:
 *
 *  struct vm_struct {
 *    struct vm_region  region;
 *    unsigned long     flags;
 *    struct page **pages;
 *    unsigned int      nr_pages;
 *    unsigned long     phys_addr;
 *  };
 *
 * get_vm_area() would then call vm_region_alloc with an appropriate
 * struct vm_region head (eg):
 *
 *  struct vm_region vmalloc_head = {
 *    .vm_list    = LIST_HEAD_INIT(vmalloc_head.vm_list),
 *    .vm_start   = VMALLOC_START,
 *    .vm_end           = VMALLOC_END,
 *  };
 *
 * However, vmalloc_head.vm_start is variable (typically, it is dependent on
 * the amount of RAM found at boot time.)  I would imagine that get_vm_area()
 * would have to initialise this each time prior to calling vm_region_alloc().
 */
struct vm_region {
      struct list_head  vm_list;
      unsigned long           vm_start;
      unsigned long           vm_end;
};

static struct vm_region consistent_head = {
      .vm_list    = LIST_HEAD_INIT(consistent_head.vm_list),
      .vm_start   = CONSISTENT_BASE,
      .vm_end           = CONSISTENT_END,
};

static struct vm_region *
vm_region_alloc(struct vm_region *head, size_t size, gfp_t gfp)
{
      unsigned long addr = head->vm_start, end = head->vm_end - size;
      unsigned long flags;
      struct vm_region *c, *new;

      new = kmalloc(sizeof(struct vm_region), gfp);
      if (!new)
            goto out;

      spin_lock_irqsave(&consistent_lock, flags);

      list_for_each_entry(c, &head->vm_list, vm_list) {
            if ((addr + size) < addr)
                  goto nospc;
            if ((addr + size) <= c->vm_start)
                  goto found;
            addr = c->vm_end;
            if (addr > end)
                  goto nospc;
      }

 found:
      /*
       * Insert this entry _before_ the one we found.
       */
      list_add_tail(&new->vm_list, &c->vm_list);
      new->vm_start = addr;
      new->vm_end = addr + size;

      spin_unlock_irqrestore(&consistent_lock, flags);
      return new;

 nospc:
      spin_unlock_irqrestore(&consistent_lock, flags);
      kfree(new);
 out:
      return NULL;
}

static struct vm_region *vm_region_find(struct vm_region *head, unsigned long addr)
{
      struct vm_region *c;

      list_for_each_entry(c, &head->vm_list, vm_list) {
            if (c->vm_start == addr)
                  goto out;
      }
      c = NULL;
 out:
      return c;
}

/*
 * Allocate DMA-coherent memory space and return both the kernel remapped
 * virtual and bus address for that space.
 */
void *
__dma_alloc_coherent(size_t size, dma_addr_t *handle, gfp_t gfp)
{
      struct page *page;
      struct vm_region *c;
      unsigned long order;
      u64 mask = 0x00ffffff, limit; /* ISA default */

      if (!consistent_pte) {
            printk(KERN_ERR "%s: not initialised\n", __func__);
            dump_stack();
            return NULL;
      }

      size = PAGE_ALIGN(size);
      limit = (mask + 1) & ~mask;
      if ((limit && size >= limit) || size >= (CONSISTENT_END - CONSISTENT_BASE)) {
            printk(KERN_WARNING "coherent allocation too big (requested %#x mask %#Lx)\n",
                   size, mask);
            return NULL;
      }

      order = get_order(size);

      if (mask != 0xffffffff)
            gfp |= GFP_DMA;

      page = alloc_pages(gfp, order);
      if (!page)
            goto no_page;

      /*
       * Invalidate any data that might be lurking in the
       * kernel direct-mapped region for device DMA.
       */
      {
            unsigned long kaddr = (unsigned long)page_address(page);
            memset(page_address(page), 0, size);
            flush_dcache_range(kaddr, kaddr + size);
      }

      /*
       * Allocate a virtual address in the consistent mapping region.
       */
      c = vm_region_alloc(&consistent_head, size,
                      gfp & ~(__GFP_DMA | __GFP_HIGHMEM));
      if (c) {
            unsigned long vaddr = c->vm_start;
            pte_t *pte = consistent_pte + CONSISTENT_OFFSET(vaddr);
            struct page *end = page + (1 << order);

            split_page(page, order);

            /*
             * Set the "dma handle"
             */
            *handle = page_to_bus(page);

            do {
                  BUG_ON(!pte_none(*pte));

                  SetPageReserved(page);
                  set_pte_at(&init_mm, vaddr,
                           pte, mk_pte(page, pgprot_noncached(PAGE_KERNEL)));
                  page++;
                  pte++;
                  vaddr += PAGE_SIZE;
            } while (size -= PAGE_SIZE);

            /*
             * Free the otherwise unused pages.
             */
            while (page < end) {
                  __free_page(page);
                  page++;
            }

            return (void *)c->vm_start;
      }

      if (page)
            __free_pages(page, order);
 no_page:
      return NULL;
}
EXPORT_SYMBOL(__dma_alloc_coherent);

/*
 * free a page as defined by the above mapping.
 */
void __dma_free_coherent(size_t size, void *vaddr)
{
      struct vm_region *c;
      unsigned long flags, addr;
      pte_t *ptep;

      size = PAGE_ALIGN(size);

      spin_lock_irqsave(&consistent_lock, flags);

      c = vm_region_find(&consistent_head, (unsigned long)vaddr);
      if (!c)
            goto no_area;

      if ((c->vm_end - c->vm_start) != size) {
            printk(KERN_ERR "%s: freeing wrong coherent size (%ld != %d)\n",
                   __func__, c->vm_end - c->vm_start, size);
            dump_stack();
            size = c->vm_end - c->vm_start;
      }

      ptep = consistent_pte + CONSISTENT_OFFSET(c->vm_start);
      addr = c->vm_start;
      do {
            pte_t pte = ptep_get_and_clear(&init_mm, addr, ptep);
            unsigned long pfn;

            ptep++;
            addr += PAGE_SIZE;

            if (!pte_none(pte) && pte_present(pte)) {
                  pfn = pte_pfn(pte);

                  if (pfn_valid(pfn)) {
                        struct page *page = pfn_to_page(pfn);
                        ClearPageReserved(page);

                        __free_page(page);
                        continue;
                  }
            }

            printk(KERN_CRIT "%s: bad page in kernel page table\n",
                   __func__);
      } while (size -= PAGE_SIZE);

      flush_tlb_kernel_range(c->vm_start, c->vm_end);

      list_del(&c->vm_list);

      spin_unlock_irqrestore(&consistent_lock, flags);

      kfree(c);
      return;

 no_area:
      spin_unlock_irqrestore(&consistent_lock, flags);
      printk(KERN_ERR "%s: trying to free invalid coherent area: %p\n",
             __func__, vaddr);
      dump_stack();
}
EXPORT_SYMBOL(__dma_free_coherent);

/*
 * Initialise the consistent memory allocation.
 */
static int __init dma_alloc_init(void)
{
      pgd_t *pgd;
      pud_t *pud;
      pmd_t *pmd;
      pte_t *pte;
      int ret = 0;

      do {
            pgd = pgd_offset(&init_mm, CONSISTENT_BASE);
            pud = pud_alloc(&init_mm, pgd, CONSISTENT_BASE);
            pmd = pmd_alloc(&init_mm, pud, CONSISTENT_BASE);
            if (!pmd) {
                  printk(KERN_ERR "%s: no pmd tables\n", __func__);
                  ret = -ENOMEM;
                  break;
            }
            WARN_ON(!pmd_none(*pmd));

            pte = pte_alloc_kernel(pmd, CONSISTENT_BASE);
            if (!pte) {
                  printk(KERN_ERR "%s: no pte tables\n", __func__);
                  ret = -ENOMEM;
                  break;
            }

            consistent_pte = pte;
      } while (0);

      return ret;
}

core_initcall(dma_alloc_init);

/*
 * make an area consistent.
 */
void __dma_sync(void *vaddr, size_t size, int direction)
{
      unsigned long start = (unsigned long)vaddr;
      unsigned long end   = start + size;

      switch (direction) {
      case DMA_NONE:
            BUG();
      case DMA_FROM_DEVICE:
            /*
             * invalidate only when cache-line aligned otherwise there is
             * the potential for discarding uncommitted data from the cache
             */
            if ((start & (L1_CACHE_BYTES - 1)) || (size & (L1_CACHE_BYTES - 1)))
                  flush_dcache_range(start, end);
            else
                  invalidate_dcache_range(start, end);
            break;
      case DMA_TO_DEVICE:           /* writeback only */
            clean_dcache_range(start, end);
            break;
      case DMA_BIDIRECTIONAL: /* writeback and invalidate */
            flush_dcache_range(start, end);
            break;
      }
}
EXPORT_SYMBOL(__dma_sync);

#ifdef CONFIG_HIGHMEM
/*
 * __dma_sync_page() implementation for systems using highmem.
 * In this case, each page of a buffer must be kmapped/kunmapped
 * in order to have a virtual address for __dma_sync(). This must
 * not sleep so kmap_atomic()/kunmap_atomic() are used.
 *
 * Note: yes, it is possible and correct to have a buffer extend
 * beyond the first page.
 */
static inline void __dma_sync_page_highmem(struct page *page,
            unsigned long offset, size_t size, int direction)
{
      size_t seg_size = min((size_t)(PAGE_SIZE - offset), size);
      size_t cur_size = seg_size;
      unsigned long flags, start, seg_offset = offset;
      int nr_segs = 1 + ((size - seg_size) + PAGE_SIZE - 1)/PAGE_SIZE;
      int seg_nr = 0;

      local_irq_save(flags);

      do {
            start = (unsigned long)kmap_atomic(page + seg_nr,
                        KM_PPC_SYNC_PAGE) + seg_offset;

            /* Sync this buffer segment */
            __dma_sync((void *)start, seg_size, direction);
            kunmap_atomic((void *)start, KM_PPC_SYNC_PAGE);
            seg_nr++;

            /* Calculate next buffer segment size */
            seg_size = min((size_t)PAGE_SIZE, size - cur_size);

            /* Add the segment size to our running total */
            cur_size += seg_size;
            seg_offset = 0;
      } while (seg_nr < nr_segs);

      local_irq_restore(flags);
}
#endif /* CONFIG_HIGHMEM */

/*
 * __dma_sync_page makes memory consistent. identical to __dma_sync, but
 * takes a struct page instead of a virtual address
 */
void __dma_sync_page(struct page *page, unsigned long offset,
      size_t size, int direction)
{
#ifdef CONFIG_HIGHMEM
      __dma_sync_page_highmem(page, offset, size, direction);
#else
      unsigned long start = (unsigned long)page_address(page) + offset;
      __dma_sync((void *)start, size, direction);
#endif
}
EXPORT_SYMBOL(__dma_sync_page);

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