/*
 *  Meta version derived from arch/powerpc/lib/dma-noncoherent.c
 *    Copyright (C) 2008 Imagination Technologies Ltd.
 *
 *  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/export.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/highmem.h>
#include <linux/dma-mapping.h>
#include <linux/slab.h>

#include <asm/tlbflush.h>
#include <asm/mmu.h>

#define CONSISTENT_OFFSET(x)    (((unsigned long)(x) - CONSISTENT_START) \
                                        >> PAGE_SHIFT)

static u64 get_coherent_dma_mask(struct device *dev)
{
        u64 mask = ~0ULL;

        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\n");
                        return 0;
                }
        }

        return mask;
}
/*
 * 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 metag_vm_region    region;
 *    unsigned long     flags;
 *    struct page       **pages;
 *    unsigned int      nr_pages;
 *    unsigned long     phys_addr;
 *  };
 *
 * get_vm_area() would then call metag_vm_region_alloc with an appropriate
 * struct metag_vm_region head (eg):
 *
 *  struct metag_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
 * metag_vm_region_alloc().
 */
struct metag_vm_region {
        struct list_head vm_list;
        unsigned long vm_start;
        unsigned long vm_end;
        struct page             *vm_pages;
        int                     vm_active;
};

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

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

        new = kmalloc(sizeof(struct metag_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;
        new->vm_active = 1;

        spin_unlock_irqrestore(&consistent_lock, flags);
        return new;

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

static struct metag_vm_region *metag_vm_region_find(struct metag_vm_region
                                                    *head, unsigned long addr)
{
        struct metag_vm_region *c;

        list_for_each_entry(c, &head->vm_list, vm_list) {
                if (c->vm_active && 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 metag_vm_region *c;
        unsigned long order;
        u64 mask = get_coherent_dma_mask(dev);
        u64 limit;

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

        if (!mask)
                goto no_page;
        size = PAGE_ALIGN(size);
        limit = (mask + 1) & ~mask;
        if ((limit && size >= limit)
            || size >= (CONSISTENT_END - CONSISTENT_START)) {
                pr_warn("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.
         */
        {
                void *kaddr = page_address(page);
                memset(kaddr, 0, size);
                flush_dcache_region(kaddr, size);
        }

        /*
         * Allocate a virtual address in the consistent mapping region.
         */
        c = metag_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);

                c->vm_pages = page;
                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_writecombine
                                               (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(struct device *dev, size_t size,
                       void *vaddr, dma_addr_t dma_handle)
{
        struct metag_vm_region *c;
        unsigned long flags, addr;
        pte_t *ptep;

        size = PAGE_ALIGN(size);

        spin_lock_irqsave(&consistent_lock, flags);

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

        c->vm_active = 0;
        if ((c->vm_end - c->vm_start) != size) {
                pr_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);
                                __free_reserved_page(page);
                                continue;
                        }
                }

                pr_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);
        pr_err("%s: trying to free invalid coherent area: %p\n",
               __func__, vaddr);
        dump_stack();
}
EXPORT_SYMBOL(dma_free_coherent);


static int dma_mmap(struct device *dev, struct vm_area_struct *vma,
                    void *cpu_addr, dma_addr_t dma_addr, size_t size)
{
        int ret = -ENXIO;

        unsigned long flags, user_size, kern_size;
        struct metag_vm_region *c;

        user_size = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;

        spin_lock_irqsave(&consistent_lock, flags);
        c = metag_vm_region_find(&consistent_head, (unsigned long)cpu_addr);
        spin_unlock_irqrestore(&consistent_lock, flags);

        if (c) {
                unsigned long off = vma->vm_pgoff;

                kern_size = (c->vm_end - c->vm_start) >> PAGE_SHIFT;

                if (off < kern_size &&
                    user_size <= (kern_size - off)) {
                        ret = remap_pfn_range(vma, vma->vm_start,
                                              page_to_pfn(c->vm_pages) + off,
                                              user_size << PAGE_SHIFT,
                                              vma->vm_page_prot);
                }
        }


        return ret;
}

int dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma,
                      void *cpu_addr, dma_addr_t dma_addr, size_t size)
{
        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
        return dma_mmap(dev, vma, cpu_addr, dma_addr, size);
}
EXPORT_SYMBOL(dma_mmap_coherent);

int dma_mmap_writecombine(struct device *dev, struct vm_area_struct *vma,
                          void *cpu_addr, dma_addr_t dma_addr, size_t size)
{
        vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
        return dma_mmap(dev, vma, cpu_addr, dma_addr, size);
}
EXPORT_SYMBOL(dma_mmap_writecombine);




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

        do {
                int offset = pgd_index(CONSISTENT_START);
                pgd = pgd_offset(&init_mm, CONSISTENT_START);
                pud = pud_alloc(&init_mm, pgd, CONSISTENT_START);
                pmd = pmd_alloc(&init_mm, pud, CONSISTENT_START);
                WARN_ON(!pmd_none(*pmd));

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

                pgd_k = ((pgd_t *) mmu_get_base()) + offset;
                pud_k = pud_offset(pgd_k, CONSISTENT_START);
                pmd_k = pmd_offset(pud_k, CONSISTENT_START);
                set_pmd(pmd_k, *pmd);

                consistent_pte = pte;
        } while (0);

        return ret;
}
early_initcall(dma_alloc_init);

/*
 * make an area consistent to devices.
 */
void dma_sync_for_device(void *vaddr, size_t size, int dma_direction)
{
        /*
         * Ensure any writes get through the write combiner. This is necessary
         * even with DMA_FROM_DEVICE, or the write may dirty the cache after
         * we've invalidated it and get written back during the DMA.
         */

        barrier();

        switch (dma_direction) {
        case DMA_BIDIRECTIONAL:
                /*
                 * Writeback to ensure the device can see our latest changes and
                 * so that we have no dirty lines, and invalidate the cache
                 * lines too in preparation for receiving the buffer back
                 * (dma_sync_for_cpu) later.
                 */
                flush_dcache_region(vaddr, size);
                break;
        case DMA_TO_DEVICE:
                /*
                 * Writeback to ensure the device can see our latest changes.
                 * There's no need to invalidate as the device shouldn't write
                 * to the buffer.
                 */
                writeback_dcache_region(vaddr, size);
                break;
        case DMA_FROM_DEVICE:
                /*
                 * Invalidate to ensure we have no dirty lines that could get
                 * written back during the DMA. It's also safe to flush
                 * (writeback) here if necessary.
                 */
                invalidate_dcache_region(vaddr, size);
                break;
        case DMA_NONE:
                BUG();
        }

        wmb();
}
EXPORT_SYMBOL(dma_sync_for_device);

/*
 * make an area consistent to the core.
 */
void dma_sync_for_cpu(void *vaddr, size_t size, int dma_direction)
{
        /*
         * Hardware L2 cache prefetch doesn't occur across 4K physical
         * boundaries, however according to Documentation/DMA-API-HOWTO.txt
         * kmalloc'd memory is DMA'able, so accesses in nearby memory could
         * trigger a cache fill in the DMA buffer.
         *
         * This should never cause dirty lines, so a flush or invalidate should
         * be safe to allow us to see data from the device.
         */
        if (_meta_l2c_pf_is_enabled()) {
                switch (dma_direction) {
                case DMA_BIDIRECTIONAL:
                case DMA_FROM_DEVICE:
                        invalidate_dcache_region(vaddr, size);
                        break;
                case DMA_TO_DEVICE:
                        /* The device shouldn't have written to the buffer */
                        break;
                case DMA_NONE:
                        BUG();
                }
        }

        rmb();
}
EXPORT_SYMBOL(dma_sync_for_cpu);