/*
 * arch/ppc64/kernel/iommu.c
 * Copyright (C) 2001 Mike Corrigan & Dave Engebretsen, IBM Corporation
 * 
 * Rewrite, cleanup, new allocation schemes, virtual merging: 
 * Copyright (C) 2004 Olof Johansson, IBM Corporation
 *               and  Ben. Herrenschmidt, IBM Corporation
 *
 * Dynamic DMA mapping support, bus-independent parts.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 */


#include <linux/config.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/dma-mapping.h>
#include <linux/init.h>
#include <asm/io.h>
#include <asm/prom.h>
#include <asm/iommu.h>
#include <asm/pci-bridge.h>
#include <asm/machdep.h>
#include <asm/bitops.h>

#define DBG(...)

#ifdef CONFIG_IOMMU_VMERGE
static int novmerge = 0;
#else
static int novmerge = 1;
#endif

static int __init setup_iommu(char *str)
{
        if (!strcmp(str, "novmerge"))
                novmerge = 1;
        else if (!strcmp(str, "vmerge"))
                novmerge = 0;
        return 1;
}

__setup("iommu=", setup_iommu);

static unsigned long iommu_range_alloc(struct iommu_table *tbl, unsigned long npages,
                                       unsigned long *handle)
{ 
        unsigned long n, end, i, start;
        unsigned long limit;
        int largealloc = npages > 15;
        int pass = 0;

        /* This allocator was derived from x86_64's bit string search */

        /* Sanity check */
        if (unlikely(npages) == 0) {
                if (printk_ratelimit())
                        WARN_ON(1);
                return DMA_ERROR_CODE;
        }

        if (handle && *handle)
                start = *handle;
        else
                start = largealloc ? tbl->it_largehint : tbl->it_hint;

        /* Use only half of the table for small allocs (15 pages or less) */
        limit = largealloc ? tbl->it_mapsize : tbl->it_halfpoint;

        if (largealloc && start < tbl->it_halfpoint)
                start = tbl->it_halfpoint;

        /* The case below can happen if we have a small segment appended
         * to a large, or when the previous alloc was at the very end of
         * the available space. If so, go back to the initial start.
         */
        if (start >= limit)
                start = largealloc ? tbl->it_largehint : tbl->it_hint;
        
 again:

        n = find_next_zero_bit(tbl->it_map, limit, start);
        end = n + npages;

        if (unlikely(end >= limit)) {
                if (likely(pass < 2)) {
                        /* First failure, just rescan the half of the table.
                         * Second failure, rescan the other half of the table.
                         */
                        start = (largealloc ^ pass) ? tbl->it_halfpoint : 0;
                        limit = pass ? tbl->it_mapsize : limit;
                        pass++;
                        goto again;
                } else {
                        /* Third failure, give up */
                        return DMA_ERROR_CODE;
                }
        }

        for (i = n; i < end; i++)
                if (test_bit(i, tbl->it_map)) {
                        start = i+1;
                        goto again;
                }

        for (i = n; i < end; i++)
                __set_bit(i, tbl->it_map);

        /* Bump the hint to a new block for small allocs. */
        if (largealloc) {
                /* Don't bump to new block to avoid fragmentation */
                tbl->it_largehint = end;
        } else {
                /* Overflow will be taken care of at the next allocation */
                tbl->it_hint = (end + tbl->it_blocksize - 1) &
                                ~(tbl->it_blocksize - 1);
        }

        /* Update handle for SG allocations */
        if (handle)
                *handle = end;

        return n;
}

static dma_addr_t iommu_alloc(struct iommu_table *tbl, void *page,
                       unsigned int npages, enum dma_data_direction direction)
{
        unsigned long entry, flags;
        dma_addr_t ret = DMA_ERROR_CODE;
        
        spin_lock_irqsave(&(tbl->it_lock), flags);

        entry = iommu_range_alloc(tbl, npages, NULL);

        if (unlikely(entry == DMA_ERROR_CODE)) {
                spin_unlock_irqrestore(&(tbl->it_lock), flags);
                return DMA_ERROR_CODE;
        }

        entry += tbl->it_offset;        /* Offset into real TCE table */
        ret = entry << PAGE_SHIFT;      /* Set the return dma address */

        /* Put the TCEs in the HW table */
        ppc_md.tce_build(tbl, entry, npages, (unsigned long)page & PAGE_MASK,
                         direction);


        /* Flush/invalidate TLB caches if necessary */
        if (ppc_md.tce_flush)
                ppc_md.tce_flush(tbl);

        spin_unlock_irqrestore(&(tbl->it_lock), flags);

        /* Make sure updates are seen by hardware */
        mb();

        return ret;
}

static void __iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr, 
                         unsigned int npages)
{
        unsigned long entry, free_entry;
        unsigned long i;

        entry = dma_addr >> PAGE_SHIFT;
        free_entry = entry - tbl->it_offset;

        if (((free_entry + npages) > tbl->it_mapsize) ||
            (entry < tbl->it_offset)) {
                if (printk_ratelimit()) {
                        printk(KERN_INFO "iommu_free: invalid entry\n");
                        printk(KERN_INFO "\tentry     = 0x%lx\n", entry); 
                        printk(KERN_INFO "\tdma_addr  = 0x%lx\n", (u64)dma_addr);
                        printk(KERN_INFO "\tTable     = 0x%lx\n", (u64)tbl);
                        printk(KERN_INFO "\tbus#      = 0x%lx\n", (u64)tbl->it_busno);
                        printk(KERN_INFO "\tmapsize   = 0x%lx\n", (u64)tbl->it_mapsize);
                        printk(KERN_INFO "\tstartOff  = 0x%lx\n", (u64)tbl->it_offset);
                        printk(KERN_INFO "\tindex     = 0x%lx\n", (u64)tbl->it_index);
                        WARN_ON(1);
                }
                return;
        }

        ppc_md.tce_free(tbl, entry, npages);
        
        for (i = 0; i < npages; i++)
                __clear_bit(free_entry+i, tbl->it_map);
}

static void iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,
                unsigned int npages)
{
        unsigned long flags;

        spin_lock_irqsave(&(tbl->it_lock), flags);

        __iommu_free(tbl, dma_addr, npages);

        /* Make sure TLB cache is flushed if the HW needs it. We do
         * not do an mb() here on purpose, it is not needed on any of
         * the current platforms.
         */
        if (ppc_md.tce_flush)
                ppc_md.tce_flush(tbl);

        spin_unlock_irqrestore(&(tbl->it_lock), flags);
}

int iommu_map_sg(struct device *dev, struct iommu_table *tbl,
                struct scatterlist *sglist, int nelems,
                enum dma_data_direction direction)
{
        dma_addr_t dma_next, dma_addr;
        unsigned long flags;
        struct scatterlist *s, *outs, *segstart;
        int outcount;
        unsigned long handle;

        BUG_ON(direction == DMA_NONE);

        if ((nelems == 0) || !tbl)
                return 0;

        outs = s = segstart = &sglist[0];
        outcount = 1;
        handle = 0;

        /* Init first segment length for backout at failure */
        outs->dma_length = 0;

        DBG("mapping %d elements:\n", nelems);

        spin_lock_irqsave(&(tbl->it_lock), flags);

        for (s = outs; nelems; nelems--, s++) {
                unsigned long vaddr, npages, entry, slen;

                slen = s->length;
                /* Sanity check */
                if (slen == 0) {
                        dma_next = 0;
                        continue;
                }
                /* Allocate iommu entries for that segment */
                vaddr = (unsigned long)page_address(s->page) + s->offset;
                npages = PAGE_ALIGN(vaddr + slen) - (vaddr & PAGE_MASK);
                npages >>= PAGE_SHIFT;
                entry = iommu_range_alloc(tbl, npages, &handle);

                DBG("  - vaddr: %lx, size: %lx\n", vaddr, slen);

                /* Handle failure */
                if (unlikely(entry == DMA_ERROR_CODE)) {
                        if (printk_ratelimit())
                                printk(KERN_INFO "iommu_alloc failed, tbl %p vaddr %lx"
                                       " npages %lx\n", tbl, vaddr, npages);
                        goto failure;
                }

                /* Convert entry to a dma_addr_t */
                entry += tbl->it_offset;
                dma_addr = entry << PAGE_SHIFT;
                dma_addr |= s->offset;

                DBG("  - %lx pages, entry: %lx, dma_addr: %lx\n",
                            npages, entry, dma_addr);

                /* Insert into HW table */
                ppc_md.tce_build(tbl, entry, npages, vaddr & PAGE_MASK, direction);

                /* If we are in an open segment, try merging */
                if (segstart != s) {
                        DBG("  - trying merge...\n");
                        /* We cannot merge if:
                         * - allocated dma_addr isn't contiguous to previous allocation
                         */
                        if (novmerge || (dma_addr != dma_next)) {
                                /* Can't merge: create a new segment */
                                segstart = s;
                                outcount++; outs++;
                                DBG("    can't merge, new segment.\n");
                        } else {
                                outs->dma_length += s->length;
                                DBG("    merged, new len: %lx\n", outs->dma_length);
                        }
                }

                if (segstart == s) {
                        /* This is a new segment, fill entries */
                        DBG("  - filling new segment.\n");
                        outs->dma_address = dma_addr;
                        outs->dma_length = slen;
                }

                /* Calculate next page pointer for contiguous check */
                dma_next = dma_addr + slen;

                DBG("  - dma next is: %lx\n", dma_next);
        }

        /* Flush/invalidate TLB caches if necessary */
        if (ppc_md.tce_flush)
                ppc_md.tce_flush(tbl);

        spin_unlock_irqrestore(&(tbl->it_lock), flags);

        /* Make sure updates are seen by hardware */
        mb();

        DBG("mapped %d elements:\n", outcount);

        /* For the sake of iommu_free_sg, we clear out the length in the
         * next entry of the sglist if we didn't fill the list completely
         */
        if (outcount < nelems) {
                outs++;
                outs->dma_address = DMA_ERROR_CODE;
                outs->dma_length = 0;
        }
        return outcount;

 failure:
        for (s = &sglist[0]; s <= outs; s++) {
                if (s->dma_length != 0) {
                        unsigned long vaddr, npages;

                        vaddr = s->dma_address & PAGE_MASK;
                        npages = (PAGE_ALIGN(s->dma_address + s->dma_length) - vaddr)
                                >> PAGE_SHIFT;
                        __iommu_free(tbl, vaddr, npages);
                }
        }
        spin_unlock_irqrestore(&(tbl->it_lock), flags);
        return 0;
}


void iommu_unmap_sg(struct iommu_table *tbl, struct scatterlist *sglist,
                int nelems, enum dma_data_direction direction)
{
        unsigned long flags;

        BUG_ON(direction == DMA_NONE);

        if (!tbl)
                return;

        spin_lock_irqsave(&(tbl->it_lock), flags);

        while (nelems--) {
                unsigned int npages;
                dma_addr_t dma_handle = sglist->dma_address;

                if (sglist->dma_length == 0)
                        break;
                npages = (PAGE_ALIGN(dma_handle + sglist->dma_length)
                          - (dma_handle & PAGE_MASK)) >> PAGE_SHIFT;
                __iommu_free(tbl, dma_handle, npages);
                sglist++;
        }

        /* Flush/invalidate TLBs if necessary. As for iommu_free(), we
         * do not do an mb() here, the affected platforms do not need it
         * when freeing.
         */
        if (ppc_md.tce_flush)
                ppc_md.tce_flush(tbl);

        spin_unlock_irqrestore(&(tbl->it_lock), flags);
}

/*
 * Build a iommu_table structure.  This contains a bit map which
 * is used to manage allocation of the tce space.
 */
struct iommu_table *iommu_init_table(struct iommu_table *tbl)
{
        unsigned long sz;
        static int welcomed = 0;

        /* it_size is in pages, it_mapsize in number of entries */
        tbl->it_mapsize = (tbl->it_size << PAGE_SHIFT) / tbl->it_entrysize;

        /* Set aside 1/4 of the table for large allocations. */
        tbl->it_halfpoint = tbl->it_mapsize * 3 / 4;

        /* number of bytes needed for the bitmap */
        sz = (tbl->it_mapsize + 7) >> 3;

        tbl->it_map = (unsigned long *)__get_free_pages(GFP_ATOMIC, get_order(sz));
        if (!tbl->it_map)
                panic("iommu_init_table: Can't allocate %ld bytes\n", sz);

        memset(tbl->it_map, 0, sz);

        tbl->it_hint = 0;
        tbl->it_largehint = tbl->it_halfpoint;
        spin_lock_init(&tbl->it_lock);

        if (!welcomed) {
                printk(KERN_INFO "IOMMU table initialized, virtual merging %s\n",
                       novmerge ? "disabled" : "enabled");
                welcomed = 1;
        }

        return tbl;
}

/* Creates TCEs for a user provided buffer.  The user buffer must be
 * contiguous real kernel storage (not vmalloc).  The address of the buffer
 * passed here is the kernel (virtual) address of the buffer.  The buffer
 * need not be page aligned, the dma_addr_t returned will point to the same
 * byte within the page as vaddr.
 */
dma_addr_t iommu_map_single(struct iommu_table *tbl, void *vaddr,
                size_t size, enum dma_data_direction direction)
{
        dma_addr_t dma_handle = DMA_ERROR_CODE;
        unsigned long uaddr;
        unsigned int npages;

        BUG_ON(direction == DMA_NONE);

        uaddr = (unsigned long)vaddr;
        npages = PAGE_ALIGN(uaddr + size) - (uaddr & PAGE_MASK);
        npages >>= PAGE_SHIFT;

        if (tbl) {
                dma_handle = iommu_alloc(tbl, vaddr, npages, direction);
                if (dma_handle == DMA_ERROR_CODE) {
                        if (printk_ratelimit())  {
                                printk(KERN_INFO "iommu_alloc failed, "
                                                "tbl %p vaddr %p npages %d\n",
                                                tbl, vaddr, npages);
                        }
                } else
                        dma_handle |= (uaddr & ~PAGE_MASK);
        }

        return dma_handle;
}

void iommu_unmap_single(struct iommu_table *tbl, dma_addr_t dma_handle,
                size_t size, enum dma_data_direction direction)
{
        BUG_ON(direction == DMA_NONE);

        if (tbl)
                iommu_free(tbl, dma_handle, (PAGE_ALIGN(dma_handle + size) -
                                        (dma_handle & PAGE_MASK)) >> PAGE_SHIFT);
}

/* Allocates a contiguous real buffer and creates mappings over it.
 * Returns the virtual address of the buffer and sets dma_handle
 * to the dma address (mapping) of the first page.
 */
void *iommu_alloc_consistent(struct iommu_table *tbl, size_t size,
                dma_addr_t *dma_handle)
{
        void *ret = NULL;
        dma_addr_t mapping;
        unsigned int npages, order;

        size = PAGE_ALIGN(size);
        npages = size >> PAGE_SHIFT;
        order = get_order(size);

        /*
         * Client asked for way too much space.  This is checked later
         * anyway.  It is easier to debug here for the drivers than in
         * the tce tables.
         */
        if (order >= IOMAP_MAX_ORDER) {
                printk("iommu_alloc_consistent size too large: 0x%lx\n", size);
                return NULL;
        }

        if (!tbl)
                return NULL;

        /* Alloc enough pages (and possibly more) */
        ret = (void *)__get_free_pages(GFP_ATOMIC, order);
        if (!ret)
                return NULL;
        memset(ret, 0, size);

        /* Set up tces to cover the allocated range */
        mapping = iommu_alloc(tbl, ret, npages, DMA_BIDIRECTIONAL);
        if (mapping == DMA_ERROR_CODE) {
                free_pages((unsigned long)ret, order);
                ret = NULL;
        } else
                *dma_handle = mapping;
        return ret;
}

void iommu_free_consistent(struct iommu_table *tbl, size_t size,
                         void *vaddr, dma_addr_t dma_handle)
{
        unsigned int npages;

        if (tbl) {
                size = PAGE_ALIGN(size);
                npages = size >> PAGE_SHIFT;
                iommu_free(tbl, dma_handle, npages);
                free_pages((unsigned long)vaddr, get_order(size));
        }
}