Merge tag 'iommu-updates-v3.5' of git://git.kernel.org/pub/scm/linux/kernel/git/joro...

[mirror_ubuntu-zesty-kernel.git] / drivers / iommu / omap-iommu.c

/*
 * omap iommu: tlb and pagetable primitives
 *
 * Copyright (C) 2008-2010 Nokia Corporation
 *
 * Written by Hiroshi DOYU <Hiroshi.DOYU@nokia.com>,
 *              Paul Mundt and Toshihiro Kobayashi
 *
 * 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/err.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/clk.h>
#include <linux/platform_device.h>
#include <linux/iommu.h>
#include <linux/mutex.h>
#include <linux/spinlock.h>

#include <asm/cacheflush.h>

#include <plat/iommu.h>

#include <plat/iopgtable.h>

#define for_each_iotlb_cr(obj, n, __i, cr)                              \
        for (__i = 0;                                                   \
             (__i < (n)) && (cr = __iotlb_read_cr((obj), __i), true);   \
             __i++)

/* bitmap of the page sizes currently supported */
#define OMAP_IOMMU_PGSIZES      (SZ_4K | SZ_64K | SZ_1M | SZ_16M)

/**
 * struct omap_iommu_domain - omap iommu domain
 * @pgtable:    the page table
 * @iommu_dev:  an omap iommu device attached to this domain. only a single
 *              iommu device can be attached for now.
 * @dev:        Device using this domain.
 * @lock:       domain lock, should be taken when attaching/detaching
 */
struct omap_iommu_domain {
        u32 *pgtable;
        struct omap_iommu *iommu_dev;
        struct device *dev;
        spinlock_t lock;
};

/* accommodate the difference between omap1 and omap2/3 */
static const struct iommu_functions *arch_iommu;

static struct platform_driver omap_iommu_driver;
static struct kmem_cache *iopte_cachep;

/**
 * omap_install_iommu_arch - Install archtecure specific iommu functions
 * @ops:        a pointer to architecture specific iommu functions
 *
 * There are several kind of iommu algorithm(tlb, pagetable) among
 * omap series. This interface installs such an iommu algorighm.
 **/
int omap_install_iommu_arch(const struct iommu_functions *ops)
{
        if (arch_iommu)
                return -EBUSY;

        arch_iommu = ops;
        return 0;
}
EXPORT_SYMBOL_GPL(omap_install_iommu_arch);

/**
 * omap_uninstall_iommu_arch - Uninstall archtecure specific iommu functions
 * @ops:        a pointer to architecture specific iommu functions
 *
 * This interface uninstalls the iommu algorighm installed previously.
 **/
void omap_uninstall_iommu_arch(const struct iommu_functions *ops)
{
        if (arch_iommu != ops)
                pr_err("%s: not your arch\n", __func__);

        arch_iommu = NULL;
}
EXPORT_SYMBOL_GPL(omap_uninstall_iommu_arch);

/**
 * omap_iommu_save_ctx - Save registers for pm off-mode support
 * @dev:        client device
 **/
void omap_iommu_save_ctx(struct device *dev)
{
        struct omap_iommu *obj = dev_to_omap_iommu(dev);

        arch_iommu->save_ctx(obj);
}
EXPORT_SYMBOL_GPL(omap_iommu_save_ctx);

/**
 * omap_iommu_restore_ctx - Restore registers for pm off-mode support
 * @dev:        client device
 **/
void omap_iommu_restore_ctx(struct device *dev)
{
        struct omap_iommu *obj = dev_to_omap_iommu(dev);

        arch_iommu->restore_ctx(obj);
}
EXPORT_SYMBOL_GPL(omap_iommu_restore_ctx);

/**
 * omap_iommu_arch_version - Return running iommu arch version
 **/
u32 omap_iommu_arch_version(void)
{
        return arch_iommu->version;
}
EXPORT_SYMBOL_GPL(omap_iommu_arch_version);

static int iommu_enable(struct omap_iommu *obj)
{
        int err;

        if (!obj)
                return -EINVAL;

        if (!arch_iommu)
                return -ENODEV;

        clk_enable(obj->clk);

        err = arch_iommu->enable(obj);

        clk_disable(obj->clk);
        return err;
}

static void iommu_disable(struct omap_iommu *obj)
{
        if (!obj)
                return;

        clk_enable(obj->clk);

        arch_iommu->disable(obj);

        clk_disable(obj->clk);
}

/*
 *      TLB operations
 */
void omap_iotlb_cr_to_e(struct cr_regs *cr, struct iotlb_entry *e)
{
        BUG_ON(!cr || !e);

        arch_iommu->cr_to_e(cr, e);
}
EXPORT_SYMBOL_GPL(omap_iotlb_cr_to_e);

static inline int iotlb_cr_valid(struct cr_regs *cr)
{
        if (!cr)
                return -EINVAL;

        return arch_iommu->cr_valid(cr);
}

static inline struct cr_regs *iotlb_alloc_cr(struct omap_iommu *obj,
                                             struct iotlb_entry *e)
{
        if (!e)
                return NULL;

        return arch_iommu->alloc_cr(obj, e);
}

static u32 iotlb_cr_to_virt(struct cr_regs *cr)
{
        return arch_iommu->cr_to_virt(cr);
}

static u32 get_iopte_attr(struct iotlb_entry *e)
{
        return arch_iommu->get_pte_attr(e);
}

static u32 iommu_report_fault(struct omap_iommu *obj, u32 *da)
{
        return arch_iommu->fault_isr(obj, da);
}

static void iotlb_lock_get(struct omap_iommu *obj, struct iotlb_lock *l)
{
        u32 val;

        val = iommu_read_reg(obj, MMU_LOCK);

        l->base = MMU_LOCK_BASE(val);
        l->vict = MMU_LOCK_VICT(val);

}

static void iotlb_lock_set(struct omap_iommu *obj, struct iotlb_lock *l)
{
        u32 val;

        val = (l->base << MMU_LOCK_BASE_SHIFT);
        val |= (l->vict << MMU_LOCK_VICT_SHIFT);

        iommu_write_reg(obj, val, MMU_LOCK);
}

static void iotlb_read_cr(struct omap_iommu *obj, struct cr_regs *cr)
{
        arch_iommu->tlb_read_cr(obj, cr);
}

static void iotlb_load_cr(struct omap_iommu *obj, struct cr_regs *cr)
{
        arch_iommu->tlb_load_cr(obj, cr);

        iommu_write_reg(obj, 1, MMU_FLUSH_ENTRY);
        iommu_write_reg(obj, 1, MMU_LD_TLB);
}

/**
 * iotlb_dump_cr - Dump an iommu tlb entry into buf
 * @obj:        target iommu
 * @cr:         contents of cam and ram register
 * @buf:        output buffer
 **/
static inline ssize_t iotlb_dump_cr(struct omap_iommu *obj, struct cr_regs *cr,
                                    char *buf)
{
        BUG_ON(!cr || !buf);

        return arch_iommu->dump_cr(obj, cr, buf);
}

/* only used in iotlb iteration for-loop */
static struct cr_regs __iotlb_read_cr(struct omap_iommu *obj, int n)
{
        struct cr_regs cr;
        struct iotlb_lock l;

        iotlb_lock_get(obj, &l);
        l.vict = n;
        iotlb_lock_set(obj, &l);
        iotlb_read_cr(obj, &cr);

        return cr;
}

/**
 * load_iotlb_entry - Set an iommu tlb entry
 * @obj:        target iommu
 * @e:          an iommu tlb entry info
 **/
#ifdef PREFETCH_IOTLB
static int load_iotlb_entry(struct omap_iommu *obj, struct iotlb_entry *e)
{
        int err = 0;
        struct iotlb_lock l;
        struct cr_regs *cr;

        if (!obj || !obj->nr_tlb_entries || !e)
                return -EINVAL;

        clk_enable(obj->clk);

        iotlb_lock_get(obj, &l);
        if (l.base == obj->nr_tlb_entries) {
                dev_warn(obj->dev, "%s: preserve entries full\n", __func__);
                err = -EBUSY;
                goto out;
        }
        if (!e->prsvd) {
                int i;
                struct cr_regs tmp;

                for_each_iotlb_cr(obj, obj->nr_tlb_entries, i, tmp)
                        if (!iotlb_cr_valid(&tmp))
                                break;

                if (i == obj->nr_tlb_entries) {
                        dev_dbg(obj->dev, "%s: full: no entry\n", __func__);
                        err = -EBUSY;
                        goto out;
                }

                iotlb_lock_get(obj, &l);
        } else {
                l.vict = l.base;
                iotlb_lock_set(obj, &l);
        }

        cr = iotlb_alloc_cr(obj, e);
        if (IS_ERR(cr)) {
                clk_disable(obj->clk);
                return PTR_ERR(cr);
        }

        iotlb_load_cr(obj, cr);
        kfree(cr);

        if (e->prsvd)
                l.base++;
        /* increment victim for next tlb load */
        if (++l.vict == obj->nr_tlb_entries)
                l.vict = l.base;
        iotlb_lock_set(obj, &l);
out:
        clk_disable(obj->clk);
        return err;
}

#else /* !PREFETCH_IOTLB */

static int load_iotlb_entry(struct omap_iommu *obj, struct iotlb_entry *e)
{
        return 0;
}

#endif /* !PREFETCH_IOTLB */

static int prefetch_iotlb_entry(struct omap_iommu *obj, struct iotlb_entry *e)
{
        return load_iotlb_entry(obj, e);
}

/**
 * flush_iotlb_page - Clear an iommu tlb entry
 * @obj:        target iommu
 * @da:         iommu device virtual address
 *
 * Clear an iommu tlb entry which includes 'da' address.
 **/
static void flush_iotlb_page(struct omap_iommu *obj, u32 da)
{
        int i;
        struct cr_regs cr;

        clk_enable(obj->clk);

        for_each_iotlb_cr(obj, obj->nr_tlb_entries, i, cr) {
                u32 start;
                size_t bytes;

                if (!iotlb_cr_valid(&cr))
                        continue;

                start = iotlb_cr_to_virt(&cr);
                bytes = iopgsz_to_bytes(cr.cam & 3);

                if ((start <= da) && (da < start + bytes)) {
                        dev_dbg(obj->dev, "%s: %08x<=%08x(%x)\n",
                                __func__, start, da, bytes);
                        iotlb_load_cr(obj, &cr);
                        iommu_write_reg(obj, 1, MMU_FLUSH_ENTRY);
                }
        }
        clk_disable(obj->clk);

        if (i == obj->nr_tlb_entries)
                dev_dbg(obj->dev, "%s: no page for %08x\n", __func__, da);
}

/**
 * flush_iotlb_all - Clear all iommu tlb entries
 * @obj:        target iommu
 **/
static void flush_iotlb_all(struct omap_iommu *obj)
{
        struct iotlb_lock l;

        clk_enable(obj->clk);

        l.base = 0;
        l.vict = 0;
        iotlb_lock_set(obj, &l);

        iommu_write_reg(obj, 1, MMU_GFLUSH);

        clk_disable(obj->clk);
}

#if defined(CONFIG_OMAP_IOMMU_DEBUG) || defined(CONFIG_OMAP_IOMMU_DEBUG_MODULE)

ssize_t omap_iommu_dump_ctx(struct omap_iommu *obj, char *buf, ssize_t bytes)
{
        if (!obj || !buf)
                return -EINVAL;

        clk_enable(obj->clk);

        bytes = arch_iommu->dump_ctx(obj, buf, bytes);

        clk_disable(obj->clk);

        return bytes;
}
EXPORT_SYMBOL_GPL(omap_iommu_dump_ctx);

static int
__dump_tlb_entries(struct omap_iommu *obj, struct cr_regs *crs, int num)
{
        int i;
        struct iotlb_lock saved;
        struct cr_regs tmp;
        struct cr_regs *p = crs;

        clk_enable(obj->clk);
        iotlb_lock_get(obj, &saved);

        for_each_iotlb_cr(obj, num, i, tmp) {
                if (!iotlb_cr_valid(&tmp))
                        continue;
                *p++ = tmp;
        }

        iotlb_lock_set(obj, &saved);
        clk_disable(obj->clk);

        return  p - crs;
}

/**
 * omap_dump_tlb_entries - dump cr arrays to given buffer
 * @obj:        target iommu
 * @buf:        output buffer
 **/
size_t omap_dump_tlb_entries(struct omap_iommu *obj, char *buf, ssize_t bytes)
{
        int i, num;
        struct cr_regs *cr;
        char *p = buf;

        num = bytes / sizeof(*cr);
        num = min(obj->nr_tlb_entries, num);

        cr = kcalloc(num, sizeof(*cr), GFP_KERNEL);
        if (!cr)
                return 0;

        num = __dump_tlb_entries(obj, cr, num);
        for (i = 0; i < num; i++)
                p += iotlb_dump_cr(obj, cr + i, p);
        kfree(cr);

        return p - buf;
}
EXPORT_SYMBOL_GPL(omap_dump_tlb_entries);

int omap_foreach_iommu_device(void *data, int (*fn)(struct device *, void *))
{
        return driver_for_each_device(&omap_iommu_driver.driver,
                                      NULL, data, fn);
}
EXPORT_SYMBOL_GPL(omap_foreach_iommu_device);

#endif /* CONFIG_OMAP_IOMMU_DEBUG_MODULE */

/*
 *      H/W pagetable operations
 */
static void flush_iopgd_range(u32 *first, u32 *last)
{
        /* FIXME: L2 cache should be taken care of if it exists */
        do {
                asm("mcr        p15, 0, %0, c7, c10, 1 @ flush_pgd"
                    : : "r" (first));
                first += L1_CACHE_BYTES / sizeof(*first);
        } while (first <= last);
}

static void flush_iopte_range(u32 *first, u32 *last)
{
        /* FIXME: L2 cache should be taken care of if it exists */
        do {
                asm("mcr        p15, 0, %0, c7, c10, 1 @ flush_pte"
                    : : "r" (first));
                first += L1_CACHE_BYTES / sizeof(*first);
        } while (first <= last);
}

static void iopte_free(u32 *iopte)
{
        /* Note: freed iopte's must be clean ready for re-use */
        kmem_cache_free(iopte_cachep, iopte);
}

static u32 *iopte_alloc(struct omap_iommu *obj, u32 *iopgd, u32 da)
{
        u32 *iopte;

        /* a table has already existed */
        if (*iopgd)
                goto pte_ready;

        /*
         * do the allocation outside the page table lock
         */
        spin_unlock(&obj->page_table_lock);
        iopte = kmem_cache_zalloc(iopte_cachep, GFP_KERNEL);
        spin_lock(&obj->page_table_lock);

        if (!*iopgd) {
                if (!iopte)
                        return ERR_PTR(-ENOMEM);

                *iopgd = virt_to_phys(iopte) | IOPGD_TABLE;
                flush_iopgd_range(iopgd, iopgd);

                dev_vdbg(obj->dev, "%s: a new pte:%p\n", __func__, iopte);
        } else {
                /* We raced, free the reduniovant table */
                iopte_free(iopte);
        }

pte_ready:
        iopte = iopte_offset(iopgd, da);

        dev_vdbg(obj->dev,
                 "%s: da:%08x pgd:%p *pgd:%08x pte:%p *pte:%08x\n",
                 __func__, da, iopgd, *iopgd, iopte, *iopte);

        return iopte;
}

static int iopgd_alloc_section(struct omap_iommu *obj, u32 da, u32 pa, u32 prot)
{
        u32 *iopgd = iopgd_offset(obj, da);

        if ((da | pa) & ~IOSECTION_MASK) {
                dev_err(obj->dev, "%s: %08x:%08x should aligned on %08lx\n",
                        __func__, da, pa, IOSECTION_SIZE);
                return -EINVAL;
        }

        *iopgd = (pa & IOSECTION_MASK) | prot | IOPGD_SECTION;
        flush_iopgd_range(iopgd, iopgd);
        return 0;
}

static int iopgd_alloc_super(struct omap_iommu *obj, u32 da, u32 pa, u32 prot)
{
        u32 *iopgd = iopgd_offset(obj, da);
        int i;

        if ((da | pa) & ~IOSUPER_MASK) {
                dev_err(obj->dev, "%s: %08x:%08x should aligned on %08lx\n",
                        __func__, da, pa, IOSUPER_SIZE);
                return -EINVAL;
        }

        for (i = 0; i < 16; i++)
                *(iopgd + i) = (pa & IOSUPER_MASK) | prot | IOPGD_SUPER;
        flush_iopgd_range(iopgd, iopgd + 15);
        return 0;
}

static int iopte_alloc_page(struct omap_iommu *obj, u32 da, u32 pa, u32 prot)
{
        u32 *iopgd = iopgd_offset(obj, da);
        u32 *iopte = iopte_alloc(obj, iopgd, da);

        if (IS_ERR(iopte))
                return PTR_ERR(iopte);

        *iopte = (pa & IOPAGE_MASK) | prot | IOPTE_SMALL;
        flush_iopte_range(iopte, iopte);

        dev_vdbg(obj->dev, "%s: da:%08x pa:%08x pte:%p *pte:%08x\n",
                 __func__, da, pa, iopte, *iopte);

        return 0;
}

static int iopte_alloc_large(struct omap_iommu *obj, u32 da, u32 pa, u32 prot)
{
        u32 *iopgd = iopgd_offset(obj, da);
        u32 *iopte = iopte_alloc(obj, iopgd, da);
        int i;

        if ((da | pa) & ~IOLARGE_MASK) {
                dev_err(obj->dev, "%s: %08x:%08x should aligned on %08lx\n",
                        __func__, da, pa, IOLARGE_SIZE);
                return -EINVAL;
        }

        if (IS_ERR(iopte))
                return PTR_ERR(iopte);

        for (i = 0; i < 16; i++)
                *(iopte + i) = (pa & IOLARGE_MASK) | prot | IOPTE_LARGE;
        flush_iopte_range(iopte, iopte + 15);
        return 0;
}

static int
iopgtable_store_entry_core(struct omap_iommu *obj, struct iotlb_entry *e)
{
        int (*fn)(struct omap_iommu *, u32, u32, u32);
        u32 prot;
        int err;

        if (!obj || !e)
                return -EINVAL;

        switch (e->pgsz) {
        case MMU_CAM_PGSZ_16M:
                fn = iopgd_alloc_super;
                break;
        case MMU_CAM_PGSZ_1M:
                fn = iopgd_alloc_section;
                break;
        case MMU_CAM_PGSZ_64K:
                fn = iopte_alloc_large;
                break;
        case MMU_CAM_PGSZ_4K:
                fn = iopte_alloc_page;
                break;
        default:
                fn = NULL;
                BUG();
                break;
        }

        prot = get_iopte_attr(e);

        spin_lock(&obj->page_table_lock);
        err = fn(obj, e->da, e->pa, prot);
        spin_unlock(&obj->page_table_lock);

        return err;
}

/**
 * omap_iopgtable_store_entry - Make an iommu pte entry
 * @obj:        target iommu
 * @e:          an iommu tlb entry info
 **/
int omap_iopgtable_store_entry(struct omap_iommu *obj, struct iotlb_entry *e)
{
        int err;

        flush_iotlb_page(obj, e->da);
        err = iopgtable_store_entry_core(obj, e);
        if (!err)
                prefetch_iotlb_entry(obj, e);
        return err;
}
EXPORT_SYMBOL_GPL(omap_iopgtable_store_entry);

/**
 * iopgtable_lookup_entry - Lookup an iommu pte entry
 * @obj:        target iommu
 * @da:         iommu device virtual address
 * @ppgd:       iommu pgd entry pointer to be returned
 * @ppte:       iommu pte entry pointer to be returned
 **/
static void
iopgtable_lookup_entry(struct omap_iommu *obj, u32 da, u32 **ppgd, u32 **ppte)
{
        u32 *iopgd, *iopte = NULL;

        iopgd = iopgd_offset(obj, da);
        if (!*iopgd)
                goto out;

        if (iopgd_is_table(*iopgd))
                iopte = iopte_offset(iopgd, da);
out:
        *ppgd = iopgd;
        *ppte = iopte;
}

static size_t iopgtable_clear_entry_core(struct omap_iommu *obj, u32 da)
{
        size_t bytes;
        u32 *iopgd = iopgd_offset(obj, da);
        int nent = 1;

        if (!*iopgd)
                return 0;

        if (iopgd_is_table(*iopgd)) {
                int i;
                u32 *iopte = iopte_offset(iopgd, da);

                bytes = IOPTE_SIZE;
                if (*iopte & IOPTE_LARGE) {
                        nent *= 16;
                        /* rewind to the 1st entry */
                        iopte = iopte_offset(iopgd, (da & IOLARGE_MASK));
                }
                bytes *= nent;
                memset(iopte, 0, nent * sizeof(*iopte));
                flush_iopte_range(iopte, iopte + (nent - 1) * sizeof(*iopte));

                /*
                 * do table walk to check if this table is necessary or not
                 */
                iopte = iopte_offset(iopgd, 0);
                for (i = 0; i < PTRS_PER_IOPTE; i++)
                        if (iopte[i])
                                goto out;

                iopte_free(iopte);
                nent = 1; /* for the next L1 entry */
        } else {
                bytes = IOPGD_SIZE;
                if ((*iopgd & IOPGD_SUPER) == IOPGD_SUPER) {
                        nent *= 16;
                        /* rewind to the 1st entry */
                        iopgd = iopgd_offset(obj, (da & IOSUPER_MASK));
                }
                bytes *= nent;
        }
        memset(iopgd, 0, nent * sizeof(*iopgd));
        flush_iopgd_range(iopgd, iopgd + (nent - 1) * sizeof(*iopgd));
out:
        return bytes;
}

/**
 * iopgtable_clear_entry - Remove an iommu pte entry
 * @obj:        target iommu
 * @da:         iommu device virtual address
 **/
static size_t iopgtable_clear_entry(struct omap_iommu *obj, u32 da)
{
        size_t bytes;

        spin_lock(&obj->page_table_lock);

        bytes = iopgtable_clear_entry_core(obj, da);
        flush_iotlb_page(obj, da);

        spin_unlock(&obj->page_table_lock);

        return bytes;
}

static void iopgtable_clear_entry_all(struct omap_iommu *obj)
{
        int i;

        spin_lock(&obj->page_table_lock);

        for (i = 0; i < PTRS_PER_IOPGD; i++) {
                u32 da;
                u32 *iopgd;

                da = i << IOPGD_SHIFT;
                iopgd = iopgd_offset(obj, da);

                if (!*iopgd)
                        continue;

                if (iopgd_is_table(*iopgd))
                        iopte_free(iopte_offset(iopgd, 0));

                *iopgd = 0;
                flush_iopgd_range(iopgd, iopgd);
        }

        flush_iotlb_all(obj);

        spin_unlock(&obj->page_table_lock);
}

/*
 *      Device IOMMU generic operations
 */
static irqreturn_t iommu_fault_handler(int irq, void *data)
{
        u32 da, errs;
        u32 *iopgd, *iopte;
        struct omap_iommu *obj = data;
        struct iommu_domain *domain = obj->domain;

        if (!obj->refcount)
                return IRQ_NONE;

        clk_enable(obj->clk);
        errs = iommu_report_fault(obj, &da);
        clk_disable(obj->clk);
        if (errs == 0)
                return IRQ_HANDLED;

        /* Fault callback or TLB/PTE Dynamic loading */
        if (!report_iommu_fault(domain, obj->dev, da, 0))
                return IRQ_HANDLED;

        iommu_disable(obj);

        iopgd = iopgd_offset(obj, da);

        if (!iopgd_is_table(*iopgd)) {
                dev_err(obj->dev, "%s: errs:0x%08x da:0x%08x pgd:0x%p "
                        "*pgd:px%08x\n", obj->name, errs, da, iopgd, *iopgd);
                return IRQ_NONE;
        }

        iopte = iopte_offset(iopgd, da);

        dev_err(obj->dev, "%s: errs:0x%08x da:0x%08x pgd:0x%p *pgd:0x%08x "
                "pte:0x%p *pte:0x%08x\n", obj->name, errs, da, iopgd, *iopgd,
                iopte, *iopte);

        return IRQ_NONE;
}

static int device_match_by_alias(struct device *dev, void *data)
{
        struct omap_iommu *obj = to_iommu(dev);
        const char *name = data;

        pr_debug("%s: %s %s\n", __func__, obj->name, name);

        return strcmp(obj->name, name) == 0;
}

/**
 * omap_iommu_attach() - attach iommu device to an iommu domain
 * @name:       name of target omap iommu device
 * @iopgd:      page table
 **/
static struct omap_iommu *omap_iommu_attach(const char *name, u32 *iopgd)
{
        int err = -ENOMEM;
        struct device *dev;
        struct omap_iommu *obj;

        dev = driver_find_device(&omap_iommu_driver.driver, NULL,
                                (void *)name,
                                device_match_by_alias);
        if (!dev)
                return NULL;

        obj = to_iommu(dev);

        spin_lock(&obj->iommu_lock);

        /* an iommu device can only be attached once */
        if (++obj->refcount > 1) {
                dev_err(dev, "%s: already attached!\n", obj->name);
                err = -EBUSY;
                goto err_enable;
        }

        obj->iopgd = iopgd;
        err = iommu_enable(obj);
        if (err)
                goto err_enable;
        flush_iotlb_all(obj);

        if (!try_module_get(obj->owner))
                goto err_module;

        spin_unlock(&obj->iommu_lock);

        dev_dbg(obj->dev, "%s: %s\n", __func__, obj->name);
        return obj;

err_module:
        if (obj->refcount == 1)
                iommu_disable(obj);
err_enable:
        obj->refcount--;
        spin_unlock(&obj->iommu_lock);
        return ERR_PTR(err);
}

/**
 * omap_iommu_detach - release iommu device
 * @obj:        target iommu
 **/
static void omap_iommu_detach(struct omap_iommu *obj)
{
        if (!obj || IS_ERR(obj))
                return;

        spin_lock(&obj->iommu_lock);

        if (--obj->refcount == 0)
                iommu_disable(obj);

        module_put(obj->owner);

        obj->iopgd = NULL;

        spin_unlock(&obj->iommu_lock);

        dev_dbg(obj->dev, "%s: %s\n", __func__, obj->name);
}

/*
 *      OMAP Device MMU(IOMMU) detection
 */
static int __devinit omap_iommu_probe(struct platform_device *pdev)
{
        int err = -ENODEV;
        int irq;
        struct omap_iommu *obj;
        struct resource *res;
        struct iommu_platform_data *pdata = pdev->dev.platform_data;

        if (pdev->num_resources != 2)
                return -EINVAL;

        obj = kzalloc(sizeof(*obj) + MMU_REG_SIZE, GFP_KERNEL);
        if (!obj)
                return -ENOMEM;

        obj->clk = clk_get(&pdev->dev, pdata->clk_name);
        if (IS_ERR(obj->clk))
                goto err_clk;

        obj->nr_tlb_entries = pdata->nr_tlb_entries;
        obj->name = pdata->name;
        obj->dev = &pdev->dev;
        obj->ctx = (void *)obj + sizeof(*obj);
        obj->da_start = pdata->da_start;
        obj->da_end = pdata->da_end;

        spin_lock_init(&obj->iommu_lock);
        mutex_init(&obj->mmap_lock);
        spin_lock_init(&obj->page_table_lock);
        INIT_LIST_HEAD(&obj->mmap);

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res) {
                err = -ENODEV;
                goto err_mem;
        }

        res = request_mem_region(res->start, resource_size(res),
                                 dev_name(&pdev->dev));
        if (!res) {
                err = -EIO;
                goto err_mem;
        }

        obj->regbase = ioremap(res->start, resource_size(res));
        if (!obj->regbase) {
                err = -ENOMEM;
                goto err_ioremap;
        }

        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
                err = -ENODEV;
                goto err_irq;
        }
        err = request_irq(irq, iommu_fault_handler, IRQF_SHARED,
                          dev_name(&pdev->dev), obj);
        if (err < 0)
                goto err_irq;
        platform_set_drvdata(pdev, obj);

        dev_info(&pdev->dev, "%s registered\n", obj->name);
        return 0;

err_irq:
        iounmap(obj->regbase);
err_ioremap:
        release_mem_region(res->start, resource_size(res));
err_mem:
        clk_put(obj->clk);
err_clk:
        kfree(obj);
        return err;
}

static int __devexit omap_iommu_remove(struct platform_device *pdev)
{
        int irq;
        struct resource *res;
        struct omap_iommu *obj = platform_get_drvdata(pdev);

        platform_set_drvdata(pdev, NULL);

        iopgtable_clear_entry_all(obj);

        irq = platform_get_irq(pdev, 0);
        free_irq(irq, obj);
        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        release_mem_region(res->start, resource_size(res));
        iounmap(obj->regbase);

        clk_put(obj->clk);
        dev_info(&pdev->dev, "%s removed\n", obj->name);
        kfree(obj);
        return 0;
}

static struct platform_driver omap_iommu_driver = {
        .probe  = omap_iommu_probe,
        .remove = __devexit_p(omap_iommu_remove),
        .driver = {
                .name   = "omap-iommu",
        },
};

static void iopte_cachep_ctor(void *iopte)
{
        clean_dcache_area(iopte, IOPTE_TABLE_SIZE);
}

static int omap_iommu_map(struct iommu_domain *domain, unsigned long da,
                         phys_addr_t pa, size_t bytes, int prot)
{
        struct omap_iommu_domain *omap_domain = domain->priv;
        struct omap_iommu *oiommu = omap_domain->iommu_dev;
        struct device *dev = oiommu->dev;
        struct iotlb_entry e;
        int omap_pgsz;
        u32 ret, flags;

        /* we only support mapping a single iommu page for now */
        omap_pgsz = bytes_to_iopgsz(bytes);
        if (omap_pgsz < 0) {
                dev_err(dev, "invalid size to map: %d\n", bytes);
                return -EINVAL;
        }

        dev_dbg(dev, "mapping da 0x%lx to pa 0x%x size 0x%x\n", da, pa, bytes);

        flags = omap_pgsz | prot;

        iotlb_init_entry(&e, da, pa, flags);

        ret = omap_iopgtable_store_entry(oiommu, &e);
        if (ret)
                dev_err(dev, "omap_iopgtable_store_entry failed: %d\n", ret);

        return ret;
}

static size_t omap_iommu_unmap(struct iommu_domain *domain, unsigned long da,
                            size_t size)
{
        struct omap_iommu_domain *omap_domain = domain->priv;
        struct omap_iommu *oiommu = omap_domain->iommu_dev;
        struct device *dev = oiommu->dev;

        dev_dbg(dev, "unmapping da 0x%lx size %u\n", da, size);

        return iopgtable_clear_entry(oiommu, da);
}

static int
omap_iommu_attach_dev(struct iommu_domain *domain, struct device *dev)
{
        struct omap_iommu_domain *omap_domain = domain->priv;
        struct omap_iommu *oiommu;
        struct omap_iommu_arch_data *arch_data = dev->archdata.iommu;
        int ret = 0;

        spin_lock(&omap_domain->lock);

        /* only a single device is supported per domain for now */
        if (omap_domain->iommu_dev) {
                dev_err(dev, "iommu domain is already attached\n");
                ret = -EBUSY;
                goto out;
        }

        /* get a handle to and enable the omap iommu */
        oiommu = omap_iommu_attach(arch_data->name, omap_domain->pgtable);
        if (IS_ERR(oiommu)) {
                ret = PTR_ERR(oiommu);
                dev_err(dev, "can't get omap iommu: %d\n", ret);
                goto out;
        }

        omap_domain->iommu_dev = arch_data->iommu_dev = oiommu;
        omap_domain->dev = dev;
        oiommu->domain = domain;

out:
        spin_unlock(&omap_domain->lock);
        return ret;
}

static void _omap_iommu_detach_dev(struct omap_iommu_domain *omap_domain,
                        struct device *dev)
{
        struct omap_iommu *oiommu = dev_to_omap_iommu(dev);
        struct omap_iommu_arch_data *arch_data = dev->archdata.iommu;

        /* only a single device is supported per domain for now */
        if (omap_domain->iommu_dev != oiommu) {
                dev_err(dev, "invalid iommu device\n");
                return;
        }

        iopgtable_clear_entry_all(oiommu);

        omap_iommu_detach(oiommu);

        omap_domain->iommu_dev = arch_data->iommu_dev = NULL;
        omap_domain->dev = NULL;
}

static void omap_iommu_detach_dev(struct iommu_domain *domain,
                                 struct device *dev)
{
        struct omap_iommu_domain *omap_domain = domain->priv;

        spin_lock(&omap_domain->lock);
        _omap_iommu_detach_dev(omap_domain, dev);
        spin_unlock(&omap_domain->lock);
}

static int omap_iommu_domain_init(struct iommu_domain *domain)
{
        struct omap_iommu_domain *omap_domain;

        omap_domain = kzalloc(sizeof(*omap_domain), GFP_KERNEL);
        if (!omap_domain) {
                pr_err("kzalloc failed\n");
                goto out;
        }

        omap_domain->pgtable = kzalloc(IOPGD_TABLE_SIZE, GFP_KERNEL);
        if (!omap_domain->pgtable) {
                pr_err("kzalloc failed\n");
                goto fail_nomem;
        }

        /*
         * should never fail, but please keep this around to ensure
         * we keep the hardware happy
         */
        BUG_ON(!IS_ALIGNED((long)omap_domain->pgtable, IOPGD_TABLE_SIZE));

        clean_dcache_area(omap_domain->pgtable, IOPGD_TABLE_SIZE);
        spin_lock_init(&omap_domain->lock);

        domain->priv = omap_domain;

        return 0;

fail_nomem:
        kfree(omap_domain);
out:
        return -ENOMEM;
}

static void omap_iommu_domain_destroy(struct iommu_domain *domain)
{
        struct omap_iommu_domain *omap_domain = domain->priv;

        domain->priv = NULL;

        /*
         * An iommu device is still attached
         * (currently, only one device can be attached) ?
         */
        if (omap_domain->iommu_dev)
                _omap_iommu_detach_dev(omap_domain, omap_domain->dev);

        kfree(omap_domain->pgtable);
        kfree(omap_domain);
}

static phys_addr_t omap_iommu_iova_to_phys(struct iommu_domain *domain,
                                          unsigned long da)
{
        struct omap_iommu_domain *omap_domain = domain->priv;
        struct omap_iommu *oiommu = omap_domain->iommu_dev;
        struct device *dev = oiommu->dev;
        u32 *pgd, *pte;
        phys_addr_t ret = 0;

        iopgtable_lookup_entry(oiommu, da, &pgd, &pte);

        if (pte) {
                if (iopte_is_small(*pte))
                        ret = omap_iommu_translate(*pte, da, IOPTE_MASK);
                else if (iopte_is_large(*pte))
                        ret = omap_iommu_translate(*pte, da, IOLARGE_MASK);
                else
                        dev_err(dev, "bogus pte 0x%x, da 0x%lx", *pte, da);
        } else {
                if (iopgd_is_section(*pgd))
                        ret = omap_iommu_translate(*pgd, da, IOSECTION_MASK);
                else if (iopgd_is_super(*pgd))
                        ret = omap_iommu_translate(*pgd, da, IOSUPER_MASK);
                else
                        dev_err(dev, "bogus pgd 0x%x, da 0x%lx", *pgd, da);
        }

        return ret;
}

static int omap_iommu_domain_has_cap(struct iommu_domain *domain,
                                    unsigned long cap)
{
        return 0;
}

static struct iommu_ops omap_iommu_ops = {
        .domain_init    = omap_iommu_domain_init,
        .domain_destroy = omap_iommu_domain_destroy,
        .attach_dev     = omap_iommu_attach_dev,
        .detach_dev     = omap_iommu_detach_dev,
        .map            = omap_iommu_map,
        .unmap          = omap_iommu_unmap,
        .iova_to_phys   = omap_iommu_iova_to_phys,
        .domain_has_cap = omap_iommu_domain_has_cap,
        .pgsize_bitmap  = OMAP_IOMMU_PGSIZES,
};

static int __init omap_iommu_init(void)
{
        struct kmem_cache *p;
        const unsigned long flags = SLAB_HWCACHE_ALIGN;
        size_t align = 1 << 10; /* L2 pagetable alignement */

        p = kmem_cache_create("iopte_cache", IOPTE_TABLE_SIZE, align, flags,
                              iopte_cachep_ctor);
        if (!p)
                return -ENOMEM;
        iopte_cachep = p;

        bus_set_iommu(&platform_bus_type, &omap_iommu_ops);

        return platform_driver_register(&omap_iommu_driver);
}
/* must be ready before omap3isp is probed */
subsys_initcall(omap_iommu_init);

static void __exit omap_iommu_exit(void)
{
        kmem_cache_destroy(iopte_cachep);

        platform_driver_unregister(&omap_iommu_driver);
}
module_exit(omap_iommu_exit);

MODULE_DESCRIPTION("omap iommu: tlb and pagetable primitives");
MODULE_ALIAS("platform:omap-iommu");
MODULE_AUTHOR("Hiroshi DOYU, Paul Mundt and Toshihiro Kobayashi");
MODULE_LICENSE("GPL v2");