/*
 * Copyright IBM Corp. 2012
 *
 * Author(s):
 *   Jan Glauber <jang@linux.vnet.ibm.com>
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/iommu-helper.h>
#include <linux/dma-mapping.h>
#include <linux/vmalloc.h>
#include <linux/pci.h>
#include <asm/pci_dma.h>

static struct kmem_cache *dma_region_table_cache;
static struct kmem_cache *dma_page_table_cache;
static int s390_iommu_strict;

static int zpci_refresh_global(struct zpci_dev *zdev)
{
        return zpci_refresh_trans((u64) zdev->fh << 32, zdev->start_dma,
                                  zdev->iommu_pages * PAGE_SIZE);
}

unsigned long *dma_alloc_cpu_table(void)
{
        unsigned long *table, *entry;

        table = kmem_cache_alloc(dma_region_table_cache, GFP_ATOMIC);
        if (!table)
                return NULL;

        for (entry = table; entry < table + ZPCI_TABLE_ENTRIES; entry++)
                *entry = ZPCI_TABLE_INVALID;
        return table;
}

static void dma_free_cpu_table(void *table)
{
        kmem_cache_free(dma_region_table_cache, table);
}

static unsigned long *dma_alloc_page_table(void)
{
        unsigned long *table, *entry;

        table = kmem_cache_alloc(dma_page_table_cache, GFP_ATOMIC);
        if (!table)
                return NULL;

        for (entry = table; entry < table + ZPCI_PT_ENTRIES; entry++)
                *entry = ZPCI_PTE_INVALID;
        return table;
}

static void dma_free_page_table(void *table)
{
        kmem_cache_free(dma_page_table_cache, table);
}

static unsigned long *dma_get_seg_table_origin(unsigned long *entry)
{
        unsigned long *sto;

        if (reg_entry_isvalid(*entry))
                sto = get_rt_sto(*entry);
        else {
                sto = dma_alloc_cpu_table();
                if (!sto)
                        return NULL;

                set_rt_sto(entry, sto);
                validate_rt_entry(entry);
                entry_clr_protected(entry);
        }
        return sto;
}

static unsigned long *dma_get_page_table_origin(unsigned long *entry)
{
        unsigned long *pto;

        if (reg_entry_isvalid(*entry))
                pto = get_st_pto(*entry);
        else {
                pto = dma_alloc_page_table();
                if (!pto)
                        return NULL;
                set_st_pto(entry, pto);
                validate_st_entry(entry);
                entry_clr_protected(entry);
        }
        return pto;
}

unsigned long *dma_walk_cpu_trans(unsigned long *rto, dma_addr_t dma_addr)
{
        unsigned long *sto, *pto;
        unsigned int rtx, sx, px;

        rtx = calc_rtx(dma_addr);
        sto = dma_get_seg_table_origin(&rto[rtx]);
        if (!sto)
                return NULL;

        sx = calc_sx(dma_addr);
        pto = dma_get_page_table_origin(&sto[sx]);
        if (!pto)
                return NULL;

        px = calc_px(dma_addr);
        return &pto[px];
}

void dma_update_cpu_trans(unsigned long *entry, void *page_addr, int flags)
{
        if (flags & ZPCI_PTE_INVALID) {
                invalidate_pt_entry(entry);
        } else {
                set_pt_pfaa(entry, page_addr);
                validate_pt_entry(entry);
        }

        if (flags & ZPCI_TABLE_PROTECTED)
                entry_set_protected(entry);
        else
                entry_clr_protected(entry);
}

static int dma_update_trans(struct zpci_dev *zdev, unsigned long pa,
                            dma_addr_t dma_addr, size_t size, int flags)
{
        unsigned int nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
        u8 *page_addr = (u8 *) (pa & PAGE_MASK);
        dma_addr_t start_dma_addr = dma_addr;
        unsigned long irq_flags;
        unsigned long *entry;
        int i, rc = 0;

        if (!nr_pages)
                return -EINVAL;

        spin_lock_irqsave(&zdev->dma_table_lock, irq_flags);
        if (!zdev->dma_table) {
                rc = -EINVAL;
                goto no_refresh;
        }

        for (i = 0; i < nr_pages; i++) {
                entry = dma_walk_cpu_trans(zdev->dma_table, dma_addr);
                if (!entry) {
                        rc = -ENOMEM;
                        goto undo_cpu_trans;
                }
                dma_update_cpu_trans(entry, page_addr, flags);
                page_addr += PAGE_SIZE;
                dma_addr += PAGE_SIZE;
        }

        /*
         * With zdev->tlb_refresh == 0, rpcit is not required to establish new
         * translations when previously invalid translation-table entries are
         * validated. With lazy unmap, it also is skipped for previously valid
         * entries, but a global rpcit is then required before any address can
         * be re-used, i.e. after each iommu bitmap wrap-around.
         */
        if (!zdev->tlb_refresh &&
                        (!s390_iommu_strict ||
                        ((flags & ZPCI_PTE_VALID_MASK) == ZPCI_PTE_VALID)))
                goto no_refresh;

        rc = zpci_refresh_trans((u64) zdev->fh << 32, start_dma_addr,
                                nr_pages * PAGE_SIZE);
undo_cpu_trans:
        if (rc && ((flags & ZPCI_PTE_VALID_MASK) == ZPCI_PTE_VALID)) {
                flags = ZPCI_PTE_INVALID;
                while (i-- > 0) {
                        page_addr -= PAGE_SIZE;
                        dma_addr -= PAGE_SIZE;
                        entry = dma_walk_cpu_trans(zdev->dma_table, dma_addr);
                        if (!entry)
                                break;
                        dma_update_cpu_trans(entry, page_addr, flags);
                }
        }

no_refresh:
        spin_unlock_irqrestore(&zdev->dma_table_lock, irq_flags);
        return rc;
}

void dma_free_seg_table(unsigned long entry)
{
        unsigned long *sto = get_rt_sto(entry);
        int sx;

        for (sx = 0; sx < ZPCI_TABLE_ENTRIES; sx++)
                if (reg_entry_isvalid(sto[sx]))
                        dma_free_page_table(get_st_pto(sto[sx]));

        dma_free_cpu_table(sto);
}

void dma_cleanup_tables(unsigned long *table)
{
        int rtx;

        if (!table)
                return;

        for (rtx = 0; rtx < ZPCI_TABLE_ENTRIES; rtx++)
                if (reg_entry_isvalid(table[rtx]))
                        dma_free_seg_table(table[rtx]);

        dma_free_cpu_table(table);
}

static unsigned long __dma_alloc_iommu(struct zpci_dev *zdev,
                                       unsigned long start, int size)
{
        unsigned long boundary_size;

        boundary_size = ALIGN(dma_get_seg_boundary(&zdev->pdev->dev) + 1,
                              PAGE_SIZE) >> PAGE_SHIFT;
        return iommu_area_alloc(zdev->iommu_bitmap, zdev->iommu_pages,
                                start, size, 0, boundary_size, 0);
}

static unsigned long dma_alloc_iommu(struct zpci_dev *zdev, int size)
{
        unsigned long offset, flags;
        int wrap = 0;

        spin_lock_irqsave(&zdev->iommu_bitmap_lock, flags);
        offset = __dma_alloc_iommu(zdev, zdev->next_bit, size);
        if (offset == -1) {
                /* wrap-around */
                offset = __dma_alloc_iommu(zdev, 0, size);
                wrap = 1;
        }

        if (offset != -1) {
                zdev->next_bit = offset + size;
                if (!zdev->tlb_refresh && !s390_iommu_strict && wrap)
                        /* global flush after wrap-around with lazy unmap */
                        zpci_refresh_global(zdev);
        }
        spin_unlock_irqrestore(&zdev->iommu_bitmap_lock, flags);
        return offset;
}

static void dma_free_iommu(struct zpci_dev *zdev, unsigned long offset, int size)
{
        unsigned long flags;

        spin_lock_irqsave(&zdev->iommu_bitmap_lock, flags);
        if (!zdev->iommu_bitmap)
                goto out;
        bitmap_clear(zdev->iommu_bitmap, offset, size);
        /*
         * Lazy flush for unmap: need to move next_bit to avoid address re-use
         * until wrap-around.
         */
        if (!s390_iommu_strict && offset >= zdev->next_bit)
                zdev->next_bit = offset + size;
out:
        spin_unlock_irqrestore(&zdev->iommu_bitmap_lock, flags);
}

static inline void zpci_err_dma(unsigned long rc, unsigned long addr)
{
        struct {
                unsigned long rc;
                unsigned long addr;
        } __packed data = {rc, addr};

        zpci_err_hex(&data, sizeof(data));
}

static dma_addr_t s390_dma_map_pages(struct device *dev, struct page *page,
                                     unsigned long offset, size_t size,
                                     enum dma_data_direction direction,
                                     struct dma_attrs *attrs)
{
        struct zpci_dev *zdev = to_zpci(to_pci_dev(dev));
        unsigned long nr_pages, iommu_page_index;
        unsigned long pa = page_to_phys(page) + offset;
        int flags = ZPCI_PTE_VALID;
        dma_addr_t dma_addr;
        int ret;

        /* This rounds up number of pages based on size and offset */
        nr_pages = iommu_num_pages(pa, size, PAGE_SIZE);
        iommu_page_index = dma_alloc_iommu(zdev, nr_pages);
        if (iommu_page_index == -1) {
                ret = -ENOSPC;
                goto out_err;
        }

        /* Use rounded up size */
        size = nr_pages * PAGE_SIZE;

        dma_addr = zdev->start_dma + iommu_page_index * PAGE_SIZE;
        if (dma_addr + size > zdev->end_dma) {
                ret = -ERANGE;
                goto out_free;
        }

        if (direction == DMA_NONE || direction == DMA_TO_DEVICE)
                flags |= ZPCI_TABLE_PROTECTED;

        ret = dma_update_trans(zdev, pa, dma_addr, size, flags);
        if (ret)
                goto out_free;

        atomic64_add(nr_pages, &zdev->mapped_pages);
        return dma_addr + (offset & ~PAGE_MASK);

out_free:
        dma_free_iommu(zdev, iommu_page_index, nr_pages);
out_err:
        zpci_err("map error:\n");
        zpci_err_dma(ret, pa);
        return DMA_ERROR_CODE;
}

static void s390_dma_unmap_pages(struct device *dev, dma_addr_t dma_addr,
                                 size_t size, enum dma_data_direction direction,
                                 struct dma_attrs *attrs)
{
        struct zpci_dev *zdev = to_zpci(to_pci_dev(dev));
        unsigned long iommu_page_index;
        int npages, ret;

        npages = iommu_num_pages(dma_addr, size, PAGE_SIZE);
        dma_addr = dma_addr & PAGE_MASK;
        ret = dma_update_trans(zdev, 0, dma_addr, npages * PAGE_SIZE,
                               ZPCI_PTE_INVALID);
        if (ret) {
                zpci_err("unmap error:\n");
                zpci_err_dma(ret, dma_addr);
                return;
        }

        atomic64_add(npages, &zdev->unmapped_pages);
        iommu_page_index = (dma_addr - zdev->start_dma) >> PAGE_SHIFT;
        dma_free_iommu(zdev, iommu_page_index, npages);
}

static void *s390_dma_alloc(struct device *dev, size_t size,
                            dma_addr_t *dma_handle, gfp_t flag,
                            struct dma_attrs *attrs)
{
        struct zpci_dev *zdev = to_zpci(to_pci_dev(dev));
        struct page *page;
        unsigned long pa;
        dma_addr_t map;

        size = PAGE_ALIGN(size);
        page = alloc_pages(flag, get_order(size));
        if (!page)
                return NULL;

        pa = page_to_phys(page);
        memset((void *) pa, 0, size);

        map = s390_dma_map_pages(dev, page, pa % PAGE_SIZE,
                                 size, DMA_BIDIRECTIONAL, NULL);
        if (dma_mapping_error(dev, map)) {
                free_pages(pa, get_order(size));
                return NULL;
        }

        atomic64_add(size / PAGE_SIZE, &zdev->allocated_pages);
        if (dma_handle)
                *dma_handle = map;
        return (void *) pa;
}

static void s390_dma_free(struct device *dev, size_t size,
                          void *pa, dma_addr_t dma_handle,
                          struct dma_attrs *attrs)
{
        struct zpci_dev *zdev = to_zpci(to_pci_dev(dev));

        size = PAGE_ALIGN(size);
        atomic64_sub(size / PAGE_SIZE, &zdev->allocated_pages);
        s390_dma_unmap_pages(dev, dma_handle, size, DMA_BIDIRECTIONAL, NULL);
        free_pages((unsigned long) pa, get_order(size));
}

static int s390_dma_map_sg(struct device *dev, struct scatterlist *sg,
                           int nr_elements, enum dma_data_direction dir,
                           struct dma_attrs *attrs)
{
        int mapped_elements = 0;
        struct scatterlist *s;
        int i;

        for_each_sg(sg, s, nr_elements, i) {
                struct page *page = sg_page(s);
                s->dma_address = s390_dma_map_pages(dev, page, s->offset,
                                                    s->length, dir, NULL);
                if (!dma_mapping_error(dev, s->dma_address)) {
                        s->dma_length = s->length;
                        mapped_elements++;
                } else
                        goto unmap;
        }
out:
        return mapped_elements;

unmap:
        for_each_sg(sg, s, mapped_elements, i) {
                if (s->dma_address)
                        s390_dma_unmap_pages(dev, s->dma_address, s->dma_length,
                                             dir, NULL);
                s->dma_address = 0;
                s->dma_length = 0;
        }
        mapped_elements = 0;
        goto out;
}

static void s390_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
                              int nr_elements, enum dma_data_direction dir,
                              struct dma_attrs *attrs)
{
        struct scatterlist *s;
        int i;

        for_each_sg(sg, s, nr_elements, i) {
                s390_dma_unmap_pages(dev, s->dma_address, s->dma_length, dir, NULL);
                s->dma_address = 0;
                s->dma_length = 0;
        }
}

int zpci_dma_init_device(struct zpci_dev *zdev)
{
        int rc;

        /*
         * At this point, if the device is part of an IOMMU domain, this would
         * be a strong hint towards a bug in the IOMMU API (common) code and/or
         * simultaneous access via IOMMU and DMA API. So let's issue a warning.
         */
        WARN_ON(zdev->s390_domain);

        spin_lock_init(&zdev->iommu_bitmap_lock);
        spin_lock_init(&zdev->dma_table_lock);

        zdev->dma_table = dma_alloc_cpu_table();
        if (!zdev->dma_table) {
                rc = -ENOMEM;
                goto out_clean;
        }

        zdev->iommu_size = (unsigned long) high_memory - PAGE_OFFSET;
        zdev->iommu_pages = zdev->iommu_size >> PAGE_SHIFT;
        zdev->iommu_bitmap = vzalloc(zdev->iommu_pages / 8);
        if (!zdev->iommu_bitmap) {
                rc = -ENOMEM;
                goto out_reg;
        }

        rc = zpci_register_ioat(zdev,
                                0,
                                zdev->start_dma + PAGE_OFFSET,
                                zdev->start_dma + zdev->iommu_size - 1,
                                (u64) zdev->dma_table);
        if (rc)
                goto out_reg;
        return 0;

out_reg:
        dma_free_cpu_table(zdev->dma_table);
out_clean:
        return rc;
}

void zpci_dma_exit_device(struct zpci_dev *zdev)
{
        /*
         * At this point, if the device is part of an IOMMU domain, this would
         * be a strong hint towards a bug in the IOMMU API (common) code and/or
         * simultaneous access via IOMMU and DMA API. So let's issue a warning.
         */
        WARN_ON(zdev->s390_domain);

        zpci_unregister_ioat(zdev, 0);
        dma_cleanup_tables(zdev->dma_table);
        zdev->dma_table = NULL;
        vfree(zdev->iommu_bitmap);
        zdev->iommu_bitmap = NULL;
        zdev->next_bit = 0;
}

static int __init dma_alloc_cpu_table_caches(void)
{
        dma_region_table_cache = kmem_cache_create("PCI_DMA_region_tables",
                                        ZPCI_TABLE_SIZE, ZPCI_TABLE_ALIGN,
                                        0, NULL);
        if (!dma_region_table_cache)
                return -ENOMEM;

        dma_page_table_cache = kmem_cache_create("PCI_DMA_page_tables",
                                        ZPCI_PT_SIZE, ZPCI_PT_ALIGN,
                                        0, NULL);
        if (!dma_page_table_cache) {
                kmem_cache_destroy(dma_region_table_cache);
                return -ENOMEM;
        }
        return 0;
}

int __init zpci_dma_init(void)
{
        return dma_alloc_cpu_table_caches();
}

void zpci_dma_exit(void)
{
        kmem_cache_destroy(dma_page_table_cache);
        kmem_cache_destroy(dma_region_table_cache);
}

#define PREALLOC_DMA_DEBUG_ENTRIES      (1 << 16)

static int __init dma_debug_do_init(void)
{
        dma_debug_init(PREALLOC_DMA_DEBUG_ENTRIES);
        return 0;
}
fs_initcall(dma_debug_do_init);

struct dma_map_ops s390_dma_ops = {
        .alloc          = s390_dma_alloc,
        .free           = s390_dma_free,
        .map_sg         = s390_dma_map_sg,
        .unmap_sg       = s390_dma_unmap_sg,
        .map_page       = s390_dma_map_pages,
        .unmap_page     = s390_dma_unmap_pages,
        /* if we support direct DMA this must be conditional */
        .is_phys        = 0,
        /* dma_supported is unconditionally true without a callback */
};
EXPORT_SYMBOL_GPL(s390_dma_ops);

static int __init s390_iommu_setup(char *str)
{
        if (!strncmp(str, "strict", 6))
                s390_iommu_strict = 1;
        return 0;
}

__setup("s390_iommu=", s390_iommu_setup);