/*
   *  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/slab.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 <linux/export.h>
  
  #include <asm/tlbflush.h>
  
  #include "mmu_decl.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		(IOREMAP_TOP)
  #define CONSISTENT_END 		(CONSISTENT_BASE + 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 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 ppc_vm_region {
  	struct list_head	vm_list;
  	unsigned long		vm_start;
  	unsigned long		vm_end;
  };
  
  static struct ppc_vm_region consistent_head = {
  	.vm_list	= LIST_HEAD_INIT(consistent_head.vm_list),
  	.vm_start	= CONSISTENT_BASE,
  	.vm_end		= CONSISTENT_END,
  };
  
  static struct ppc_vm_region *
  ppc_vm_region_alloc(struct ppc_vm_region *head, size_t size, gfp_t gfp)
  {
  	unsigned long addr = head->vm_start, end = head->vm_end - size;
  	unsigned long flags;
  	struct ppc_vm_region *c, *new;
  
  	new = kmalloc(sizeof(struct ppc_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 ppc_vm_region *ppc_vm_region_find(struct ppc_vm_region *head, unsigned long addr)
  {
  	struct ppc_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(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp)
  {
  	struct page *page;
  	struct ppc_vm_region *c;
  	unsigned long order;
  	u64 mask = ISA_DMA_THRESHOLD, limit;
  
  	if (dev) {
  		mask = dev->coherent_dma_mask;
  
  		/*
  		 * Sanity check the DMA mask - it must be non-zero, and
  		 * must be able to be satisfied by a DMA allocation.
  		 */
  		if (mask == 0) {
  			dev_warn(dev, "coherent DMA mask is unset
  ");
  			goto no_page;
  		}
  
  		if ((~mask) & ISA_DMA_THRESHOLD) {
  			dev_warn(dev, "coherent DMA mask %#llx is smaller "
  				 "than system GFP_DMA mask %#llx
  ",
  				 mask, (unsigned long long)ISA_DMA_THRESHOLD);
  			goto no_page;
  		}
  	}
  
  
  	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)
  ",
  		       size, mask);
  		return NULL;
  	}
  
  	order = get_order(size);
  
  	/* Might be useful if we ever have a real legacy DMA zone... */
  	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 = ppc_vm_region_alloc(&consistent_head, size,
  			    gfp & ~(__GFP_DMA | __GFP_HIGHMEM));
  	if (c) {
  		unsigned long vaddr = c->vm_start;
  		struct page *end = page + (1 << order);
  
  		split_page(page, order);
  
  		/*
  		 * Set the "dma handle"
  		 */
  		*handle = page_to_phys(page);
  
  		do {
  			SetPageReserved(page);
  			map_page(vaddr, page_to_phys(page),
  				 pgprot_noncached(PAGE_KERNEL));
  			page++;
  			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 ppc_vm_region *c;
  	unsigned long flags, addr;
  	
  	size = PAGE_ALIGN(size);
  
  	spin_lock_irqsave(&consistent_lock, flags);
  
  	c = ppc_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)
  ",
  		       __func__, c->vm_end - c->vm_start, size);
  		dump_stack();
  		size = c->vm_end - c->vm_start;
  	}
  
  	addr = c->vm_start;
  	do {
  		pte_t *ptep;
  		unsigned long pfn;
  
  		ptep = pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(addr),
  							       addr),
  						    addr),
  					 addr);
  		if (!pte_none(*ptep) && pte_present(*ptep)) {
  			pfn = pte_pfn(*ptep);
  			pte_clear(&init_mm, addr, ptep);
  			if (pfn_valid(pfn)) {
  				struct page *page = pfn_to_page(pfn);
  				__free_reserved_page(page);
  			}
  		}
  		addr += PAGE_SIZE;
  	} 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
  ",
  	       __func__, vaddr);
  	dump_stack();
  }
  EXPORT_SYMBOL(__dma_free_coherent);
  
  /*
   * 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) + seg_offset;
  
  		/* Sync this buffer segment */
  		__dma_sync((void *)start, seg_size, direction);
  		kunmap_atomic((void *)start);
  		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);
  
  /*
   * Return the PFN for a given cpu virtual address returned by
   * __dma_alloc_coherent. This is used by dma_mmap_coherent()
   */
  unsigned long __dma_get_coherent_pfn(unsigned long cpu_addr)
  {
  	/* This should always be populated, so we don't test every
  	 * level. If that fails, we'll have a nice crash which
  	 * will be as good as a BUG_ON()
  	 */
  	pgd_t *pgd = pgd_offset_k(cpu_addr);
  	pud_t *pud = pud_offset(pgd, cpu_addr);
  	pmd_t *pmd = pmd_offset(pud, cpu_addr);
  	pte_t *ptep = pte_offset_kernel(pmd, cpu_addr);
  
  	if (pte_none(*ptep) || !pte_present(*ptep))
  		return 0;
  	return pte_pfn(*ptep);
  }