/*
 *  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 */
                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);