bootmem: factor out the marking of a PFN range

[linux-2.6/mini2440.git] / drivers / dma / iop-adma.c

/*
 * offload engine driver for the Intel Xscale series of i/o processors
 * Copyright © 2006, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope 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.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 *
 */

/*
 * This driver supports the asynchrounous DMA copy and RAID engines available
 * on the Intel Xscale(R) family of I/O Processors (IOP 32x, 33x, 134x)
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/async_tx.h>
#include <linux/delay.h>
#include <linux/dma-mapping.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/memory.h>
#include <linux/ioport.h>

#include <asm/arch/adma.h>

#define to_iop_adma_chan(chan) container_of(chan, struct iop_adma_chan, common)
#define to_iop_adma_device(dev) \
        container_of(dev, struct iop_adma_device, common)
#define tx_to_iop_adma_slot(tx) \
        container_of(tx, struct iop_adma_desc_slot, async_tx)

/**
 * iop_adma_free_slots - flags descriptor slots for reuse
 * @slot: Slot to free
 * Caller must hold &iop_chan->lock while calling this function
 */
static void iop_adma_free_slots(struct iop_adma_desc_slot *slot)
{
        int stride = slot->slots_per_op;

        while (stride--) {
                slot->slots_per_op = 0;
                slot = list_entry(slot->slot_node.next,
                                struct iop_adma_desc_slot,
                                slot_node);
        }
}

static dma_cookie_t
iop_adma_run_tx_complete_actions(struct iop_adma_desc_slot *desc,
        struct iop_adma_chan *iop_chan, dma_cookie_t cookie)
{
        BUG_ON(desc->async_tx.cookie < 0);
        if (desc->async_tx.cookie > 0) {
                cookie = desc->async_tx.cookie;
                desc->async_tx.cookie = 0;

                /* call the callback (must not sleep or submit new
                 * operations to this channel)
                 */
                if (desc->async_tx.callback)
                        desc->async_tx.callback(
                                desc->async_tx.callback_param);

                /* unmap dma addresses
                 * (unmap_single vs unmap_page?)
                 */
                if (desc->group_head && desc->unmap_len) {
                        struct iop_adma_desc_slot *unmap = desc->group_head;
                        struct device *dev =
                                &iop_chan->device->pdev->dev;
                        u32 len = unmap->unmap_len;
                        enum dma_ctrl_flags flags = desc->async_tx.flags;
                        u32 src_cnt;
                        dma_addr_t addr;

                        if (!(flags & DMA_COMPL_SKIP_DEST_UNMAP)) {
                                addr = iop_desc_get_dest_addr(unmap, iop_chan);
                                dma_unmap_page(dev, addr, len, DMA_FROM_DEVICE);
                        }

                        if (!(flags & DMA_COMPL_SKIP_SRC_UNMAP)) {
                                src_cnt = unmap->unmap_src_cnt;
                                while (src_cnt--) {
                                        addr = iop_desc_get_src_addr(unmap,
                                                                     iop_chan,
                                                                     src_cnt);
                                        dma_unmap_page(dev, addr, len,
                                                       DMA_TO_DEVICE);
                                }
                        }
                        desc->group_head = NULL;
                }
        }

        /* run dependent operations */
        async_tx_run_dependencies(&desc->async_tx);

        return cookie;
}

static int
iop_adma_clean_slot(struct iop_adma_desc_slot *desc,
        struct iop_adma_chan *iop_chan)
{
        /* the client is allowed to attach dependent operations
         * until 'ack' is set
         */
        if (!async_tx_test_ack(&desc->async_tx))
                return 0;

        /* leave the last descriptor in the chain
         * so we can append to it
         */
        if (desc->chain_node.next == &iop_chan->chain)
                return 1;

        dev_dbg(iop_chan->device->common.dev,
                "\tfree slot: %d slots_per_op: %d\n",
                desc->idx, desc->slots_per_op);

        list_del(&desc->chain_node);
        iop_adma_free_slots(desc);

        return 0;
}

static void __iop_adma_slot_cleanup(struct iop_adma_chan *iop_chan)
{
        struct iop_adma_desc_slot *iter, *_iter, *grp_start = NULL;
        dma_cookie_t cookie = 0;
        u32 current_desc = iop_chan_get_current_descriptor(iop_chan);
        int busy = iop_chan_is_busy(iop_chan);
        int seen_current = 0, slot_cnt = 0, slots_per_op = 0;

        dev_dbg(iop_chan->device->common.dev, "%s\n", __func__);
        /* free completed slots from the chain starting with
         * the oldest descriptor
         */
        list_for_each_entry_safe(iter, _iter, &iop_chan->chain,
                                        chain_node) {
                pr_debug("\tcookie: %d slot: %d busy: %d "
                        "this_desc: %#x next_desc: %#x ack: %d\n",
                        iter->async_tx.cookie, iter->idx, busy,
                        iter->async_tx.phys, iop_desc_get_next_desc(iter),
                        async_tx_test_ack(&iter->async_tx));
                prefetch(_iter);
                prefetch(&_iter->async_tx);

                /* do not advance past the current descriptor loaded into the
                 * hardware channel, subsequent descriptors are either in
                 * process or have not been submitted
                 */
                if (seen_current)
                        break;

                /* stop the search if we reach the current descriptor and the
                 * channel is busy, or if it appears that the current descriptor
                 * needs to be re-read (i.e. has been appended to)
                 */
                if (iter->async_tx.phys == current_desc) {
                        BUG_ON(seen_current++);
                        if (busy || iop_desc_get_next_desc(iter))
                                break;
                }

                /* detect the start of a group transaction */
                if (!slot_cnt && !slots_per_op) {
                        slot_cnt = iter->slot_cnt;
                        slots_per_op = iter->slots_per_op;
                        if (slot_cnt <= slots_per_op) {
                                slot_cnt = 0;
                                slots_per_op = 0;
                        }
                }

                if (slot_cnt) {
                        pr_debug("\tgroup++\n");
                        if (!grp_start)
                                grp_start = iter;
                        slot_cnt -= slots_per_op;
                }

                /* all the members of a group are complete */
                if (slots_per_op != 0 && slot_cnt == 0) {
                        struct iop_adma_desc_slot *grp_iter, *_grp_iter;
                        int end_of_chain = 0;
                        pr_debug("\tgroup end\n");

                        /* collect the total results */
                        if (grp_start->xor_check_result) {
                                u32 zero_sum_result = 0;
                                slot_cnt = grp_start->slot_cnt;
                                grp_iter = grp_start;

                                list_for_each_entry_from(grp_iter,
                                        &iop_chan->chain, chain_node) {
                                        zero_sum_result |=
                                            iop_desc_get_zero_result(grp_iter);
                                            pr_debug("\titer%d result: %d\n",
                                            grp_iter->idx, zero_sum_result);
                                        slot_cnt -= slots_per_op;
                                        if (slot_cnt == 0)
                                                break;
                                }
                                pr_debug("\tgrp_start->xor_check_result: %p\n",
                                        grp_start->xor_check_result);
                                *grp_start->xor_check_result = zero_sum_result;
                        }

                        /* clean up the group */
                        slot_cnt = grp_start->slot_cnt;
                        grp_iter = grp_start;
                        list_for_each_entry_safe_from(grp_iter, _grp_iter,
                                &iop_chan->chain, chain_node) {
                                cookie = iop_adma_run_tx_complete_actions(
                                        grp_iter, iop_chan, cookie);

                                slot_cnt -= slots_per_op;
                                end_of_chain = iop_adma_clean_slot(grp_iter,
                                        iop_chan);

                                if (slot_cnt == 0 || end_of_chain)
                                        break;
                        }

                        /* the group should be complete at this point */
                        BUG_ON(slot_cnt);

                        slots_per_op = 0;
                        grp_start = NULL;
                        if (end_of_chain)
                                break;
                        else
                                continue;
                } else if (slots_per_op) /* wait for group completion */
                        continue;

                /* write back zero sum results (single descriptor case) */
                if (iter->xor_check_result && iter->async_tx.cookie)
                        *iter->xor_check_result =
                                iop_desc_get_zero_result(iter);

                cookie = iop_adma_run_tx_complete_actions(
                                        iter, iop_chan, cookie);

                if (iop_adma_clean_slot(iter, iop_chan))
                        break;
        }

        BUG_ON(!seen_current);

        if (cookie > 0) {
                iop_chan->completed_cookie = cookie;
                pr_debug("\tcompleted cookie %d\n", cookie);
        }
}

static void
iop_adma_slot_cleanup(struct iop_adma_chan *iop_chan)
{
        spin_lock_bh(&iop_chan->lock);
        __iop_adma_slot_cleanup(iop_chan);
        spin_unlock_bh(&iop_chan->lock);
}

static void iop_adma_tasklet(unsigned long data)
{
        struct iop_adma_chan *iop_chan = (struct iop_adma_chan *) data;

        spin_lock(&iop_chan->lock);
        __iop_adma_slot_cleanup(iop_chan);
        spin_unlock(&iop_chan->lock);
}

static struct iop_adma_desc_slot *
iop_adma_alloc_slots(struct iop_adma_chan *iop_chan, int num_slots,
                        int slots_per_op)
{
        struct iop_adma_desc_slot *iter, *_iter, *alloc_start = NULL;
        LIST_HEAD(chain);
        int slots_found, retry = 0;

        /* start search from the last allocated descrtiptor
         * if a contiguous allocation can not be found start searching
         * from the beginning of the list
         */
retry:
        slots_found = 0;
        if (retry == 0)
                iter = iop_chan->last_used;
        else
                iter = list_entry(&iop_chan->all_slots,
                        struct iop_adma_desc_slot,
                        slot_node);

        list_for_each_entry_safe_continue(
                iter, _iter, &iop_chan->all_slots, slot_node) {
                prefetch(_iter);
                prefetch(&_iter->async_tx);
                if (iter->slots_per_op) {
                        /* give up after finding the first busy slot
                         * on the second pass through the list
                         */
                        if (retry)
                                break;

                        slots_found = 0;
                        continue;
                }

                /* start the allocation if the slot is correctly aligned */
                if (!slots_found++) {
                        if (iop_desc_is_aligned(iter, slots_per_op))
                                alloc_start = iter;
                        else {
                                slots_found = 0;
                                continue;
                        }
                }

                if (slots_found == num_slots) {
                        struct iop_adma_desc_slot *alloc_tail = NULL;
                        struct iop_adma_desc_slot *last_used = NULL;
                        iter = alloc_start;
                        while (num_slots) {
                                int i;
                                dev_dbg(iop_chan->device->common.dev,
                                        "allocated slot: %d "
                                        "(desc %p phys: %#x) slots_per_op %d\n",
                                        iter->idx, iter->hw_desc,
                                        iter->async_tx.phys, slots_per_op);

                                /* pre-ack all but the last descriptor */
                                if (num_slots != slots_per_op)
                                        async_tx_ack(&iter->async_tx);

                                list_add_tail(&iter->chain_node, &chain);
                                alloc_tail = iter;
                                iter->async_tx.cookie = 0;
                                iter->slot_cnt = num_slots;
                                iter->xor_check_result = NULL;
                                for (i = 0; i < slots_per_op; i++) {
                                        iter->slots_per_op = slots_per_op - i;
                                        last_used = iter;
                                        iter = list_entry(iter->slot_node.next,
                                                struct iop_adma_desc_slot,
                                                slot_node);
                                }
                                num_slots -= slots_per_op;
                        }
                        alloc_tail->group_head = alloc_start;
                        alloc_tail->async_tx.cookie = -EBUSY;
                        list_splice(&chain, &alloc_tail->async_tx.tx_list);
                        iop_chan->last_used = last_used;
                        iop_desc_clear_next_desc(alloc_start);
                        iop_desc_clear_next_desc(alloc_tail);
                        return alloc_tail;
                }
        }
        if (!retry++)
                goto retry;

        /* perform direct reclaim if the allocation fails */
        __iop_adma_slot_cleanup(iop_chan);

        return NULL;
}

static dma_cookie_t
iop_desc_assign_cookie(struct iop_adma_chan *iop_chan,
        struct iop_adma_desc_slot *desc)
{
        dma_cookie_t cookie = iop_chan->common.cookie;
        cookie++;
        if (cookie < 0)
                cookie = 1;
        iop_chan->common.cookie = desc->async_tx.cookie = cookie;
        return cookie;
}

static void iop_adma_check_threshold(struct iop_adma_chan *iop_chan)
{
        dev_dbg(iop_chan->device->common.dev, "pending: %d\n",
                iop_chan->pending);

        if (iop_chan->pending >= IOP_ADMA_THRESHOLD) {
                iop_chan->pending = 0;
                iop_chan_append(iop_chan);
        }
}

static dma_cookie_t
iop_adma_tx_submit(struct dma_async_tx_descriptor *tx)
{
        struct iop_adma_desc_slot *sw_desc = tx_to_iop_adma_slot(tx);
        struct iop_adma_chan *iop_chan = to_iop_adma_chan(tx->chan);
        struct iop_adma_desc_slot *grp_start, *old_chain_tail;
        int slot_cnt;
        int slots_per_op;
        dma_cookie_t cookie;

        grp_start = sw_desc->group_head;
        slot_cnt = grp_start->slot_cnt;
        slots_per_op = grp_start->slots_per_op;

        spin_lock_bh(&iop_chan->lock);
        cookie = iop_desc_assign_cookie(iop_chan, sw_desc);

        old_chain_tail = list_entry(iop_chan->chain.prev,
                struct iop_adma_desc_slot, chain_node);
        list_splice_init(&sw_desc->async_tx.tx_list,
                         &old_chain_tail->chain_node);

        /* fix up the hardware chain */
        iop_desc_set_next_desc(old_chain_tail, grp_start->async_tx.phys);

        /* 1/ don't add pre-chained descriptors
         * 2/ dummy read to flush next_desc write
         */
        BUG_ON(iop_desc_get_next_desc(sw_desc));

        /* increment the pending count by the number of slots
         * memcpy operations have a 1:1 (slot:operation) relation
         * other operations are heavier and will pop the threshold
         * more often.
         */
        iop_chan->pending += slot_cnt;
        iop_adma_check_threshold(iop_chan);
        spin_unlock_bh(&iop_chan->lock);

        dev_dbg(iop_chan->device->common.dev, "%s cookie: %d slot: %d\n",
                __func__, sw_desc->async_tx.cookie, sw_desc->idx);

        return cookie;
}

static void iop_chan_start_null_memcpy(struct iop_adma_chan *iop_chan);
static void iop_chan_start_null_xor(struct iop_adma_chan *iop_chan);

/**
 * iop_adma_alloc_chan_resources -  returns the number of allocated descriptors
 * @chan - allocate descriptor resources for this channel
 * @client - current client requesting the channel be ready for requests
 *
 * Note: We keep the slots for 1 operation on iop_chan->chain at all times.  To
 * avoid deadlock, via async_xor, num_descs_in_pool must at a minimum be
 * greater than 2x the number slots needed to satisfy a device->max_xor
 * request.
 * */
static int iop_adma_alloc_chan_resources(struct dma_chan *chan,
                                         struct dma_client *client)
{
        char *hw_desc;
        int idx;
        struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
        struct iop_adma_desc_slot *slot = NULL;
        int init = iop_chan->slots_allocated ? 0 : 1;
        struct iop_adma_platform_data *plat_data =
                iop_chan->device->pdev->dev.platform_data;
        int num_descs_in_pool = plat_data->pool_size/IOP_ADMA_SLOT_SIZE;

        /* Allocate descriptor slots */
        do {
                idx = iop_chan->slots_allocated;
                if (idx == num_descs_in_pool)
                        break;

                slot = kzalloc(sizeof(*slot), GFP_KERNEL);
                if (!slot) {
                        printk(KERN_INFO "IOP ADMA Channel only initialized"
                                " %d descriptor slots", idx);
                        break;
                }
                hw_desc = (char *) iop_chan->device->dma_desc_pool_virt;
                slot->hw_desc = (void *) &hw_desc[idx * IOP_ADMA_SLOT_SIZE];

                dma_async_tx_descriptor_init(&slot->async_tx, chan);
                slot->async_tx.tx_submit = iop_adma_tx_submit;
                INIT_LIST_HEAD(&slot->chain_node);
                INIT_LIST_HEAD(&slot->slot_node);
                INIT_LIST_HEAD(&slot->async_tx.tx_list);
                hw_desc = (char *) iop_chan->device->dma_desc_pool;
                slot->async_tx.phys =
                        (dma_addr_t) &hw_desc[idx * IOP_ADMA_SLOT_SIZE];
                slot->idx = idx;

                spin_lock_bh(&iop_chan->lock);
                iop_chan->slots_allocated++;
                list_add_tail(&slot->slot_node, &iop_chan->all_slots);
                spin_unlock_bh(&iop_chan->lock);
        } while (iop_chan->slots_allocated < num_descs_in_pool);

        if (idx && !iop_chan->last_used)
                iop_chan->last_used = list_entry(iop_chan->all_slots.next,
                                        struct iop_adma_desc_slot,
                                        slot_node);

        dev_dbg(iop_chan->device->common.dev,
                "allocated %d descriptor slots last_used: %p\n",
                iop_chan->slots_allocated, iop_chan->last_used);

        /* initialize the channel and the chain with a null operation */
        if (init) {
                if (dma_has_cap(DMA_MEMCPY,
                        iop_chan->device->common.cap_mask))
                        iop_chan_start_null_memcpy(iop_chan);
                else if (dma_has_cap(DMA_XOR,
                        iop_chan->device->common.cap_mask))
                        iop_chan_start_null_xor(iop_chan);
                else
                        BUG();
        }

        return (idx > 0) ? idx : -ENOMEM;
}

static struct dma_async_tx_descriptor *
iop_adma_prep_dma_interrupt(struct dma_chan *chan, unsigned long flags)
{
        struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
        struct iop_adma_desc_slot *sw_desc, *grp_start;
        int slot_cnt, slots_per_op;

        dev_dbg(iop_chan->device->common.dev, "%s\n", __func__);

        spin_lock_bh(&iop_chan->lock);
        slot_cnt = iop_chan_interrupt_slot_count(&slots_per_op, iop_chan);
        sw_desc = iop_adma_alloc_slots(iop_chan, slot_cnt, slots_per_op);
        if (sw_desc) {
                grp_start = sw_desc->group_head;
                iop_desc_init_interrupt(grp_start, iop_chan);
                grp_start->unmap_len = 0;
                sw_desc->async_tx.flags = flags;
        }
        spin_unlock_bh(&iop_chan->lock);

        return sw_desc ? &sw_desc->async_tx : NULL;
}

static struct dma_async_tx_descriptor *
iop_adma_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dma_dest,
                         dma_addr_t dma_src, size_t len, unsigned long flags)
{
        struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
        struct iop_adma_desc_slot *sw_desc, *grp_start;
        int slot_cnt, slots_per_op;

        if (unlikely(!len))
                return NULL;
        BUG_ON(unlikely(len > IOP_ADMA_MAX_BYTE_COUNT));

        dev_dbg(iop_chan->device->common.dev, "%s len: %u\n",
                __func__, len);

        spin_lock_bh(&iop_chan->lock);
        slot_cnt = iop_chan_memcpy_slot_count(len, &slots_per_op);
        sw_desc = iop_adma_alloc_slots(iop_chan, slot_cnt, slots_per_op);
        if (sw_desc) {
                grp_start = sw_desc->group_head;
                iop_desc_init_memcpy(grp_start, flags);
                iop_desc_set_byte_count(grp_start, iop_chan, len);
                iop_desc_set_dest_addr(grp_start, iop_chan, dma_dest);
                iop_desc_set_memcpy_src_addr(grp_start, dma_src);
                sw_desc->unmap_src_cnt = 1;
                sw_desc->unmap_len = len;
                sw_desc->async_tx.flags = flags;
        }
        spin_unlock_bh(&iop_chan->lock);

        return sw_desc ? &sw_desc->async_tx : NULL;
}

static struct dma_async_tx_descriptor *
iop_adma_prep_dma_memset(struct dma_chan *chan, dma_addr_t dma_dest,
                         int value, size_t len, unsigned long flags)
{
        struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
        struct iop_adma_desc_slot *sw_desc, *grp_start;
        int slot_cnt, slots_per_op;

        if (unlikely(!len))
                return NULL;
        BUG_ON(unlikely(len > IOP_ADMA_MAX_BYTE_COUNT));

        dev_dbg(iop_chan->device->common.dev, "%s len: %u\n",
                __func__, len);

        spin_lock_bh(&iop_chan->lock);
        slot_cnt = iop_chan_memset_slot_count(len, &slots_per_op);
        sw_desc = iop_adma_alloc_slots(iop_chan, slot_cnt, slots_per_op);
        if (sw_desc) {
                grp_start = sw_desc->group_head;
                iop_desc_init_memset(grp_start, flags);
                iop_desc_set_byte_count(grp_start, iop_chan, len);
                iop_desc_set_block_fill_val(grp_start, value);
                iop_desc_set_dest_addr(grp_start, iop_chan, dma_dest);
                sw_desc->unmap_src_cnt = 1;
                sw_desc->unmap_len = len;
                sw_desc->async_tx.flags = flags;
        }
        spin_unlock_bh(&iop_chan->lock);

        return sw_desc ? &sw_desc->async_tx : NULL;
}

static struct dma_async_tx_descriptor *
iop_adma_prep_dma_xor(struct dma_chan *chan, dma_addr_t dma_dest,
                      dma_addr_t *dma_src, unsigned int src_cnt, size_t len,
                      unsigned long flags)
{
        struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
        struct iop_adma_desc_slot *sw_desc, *grp_start;
        int slot_cnt, slots_per_op;

        if (unlikely(!len))
                return NULL;
        BUG_ON(unlikely(len > IOP_ADMA_XOR_MAX_BYTE_COUNT));

        dev_dbg(iop_chan->device->common.dev,
                "%s src_cnt: %d len: %u flags: %lx\n",
                __func__, src_cnt, len, flags);

        spin_lock_bh(&iop_chan->lock);
        slot_cnt = iop_chan_xor_slot_count(len, src_cnt, &slots_per_op);
        sw_desc = iop_adma_alloc_slots(iop_chan, slot_cnt, slots_per_op);
        if (sw_desc) {
                grp_start = sw_desc->group_head;
                iop_desc_init_xor(grp_start, src_cnt, flags);
                iop_desc_set_byte_count(grp_start, iop_chan, len);
                iop_desc_set_dest_addr(grp_start, iop_chan, dma_dest);
                sw_desc->unmap_src_cnt = src_cnt;
                sw_desc->unmap_len = len;
                sw_desc->async_tx.flags = flags;
                while (src_cnt--)
                        iop_desc_set_xor_src_addr(grp_start, src_cnt,
                                                  dma_src[src_cnt]);
        }
        spin_unlock_bh(&iop_chan->lock);

        return sw_desc ? &sw_desc->async_tx : NULL;
}

static struct dma_async_tx_descriptor *
iop_adma_prep_dma_zero_sum(struct dma_chan *chan, dma_addr_t *dma_src,
                           unsigned int src_cnt, size_t len, u32 *result,
                           unsigned long flags)
{
        struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
        struct iop_adma_desc_slot *sw_desc, *grp_start;
        int slot_cnt, slots_per_op;

        if (unlikely(!len))
                return NULL;

        dev_dbg(iop_chan->device->common.dev, "%s src_cnt: %d len: %u\n",
                __func__, src_cnt, len);

        spin_lock_bh(&iop_chan->lock);
        slot_cnt = iop_chan_zero_sum_slot_count(len, src_cnt, &slots_per_op);
        sw_desc = iop_adma_alloc_slots(iop_chan, slot_cnt, slots_per_op);
        if (sw_desc) {
                grp_start = sw_desc->group_head;
                iop_desc_init_zero_sum(grp_start, src_cnt, flags);
                iop_desc_set_zero_sum_byte_count(grp_start, len);
                grp_start->xor_check_result = result;
                pr_debug("\t%s: grp_start->xor_check_result: %p\n",
                        __func__, grp_start->xor_check_result);
                sw_desc->unmap_src_cnt = src_cnt;
                sw_desc->unmap_len = len;
                sw_desc->async_tx.flags = flags;
                while (src_cnt--)
                        iop_desc_set_zero_sum_src_addr(grp_start, src_cnt,
                                                       dma_src[src_cnt]);
        }
        spin_unlock_bh(&iop_chan->lock);

        return sw_desc ? &sw_desc->async_tx : NULL;
}

static void iop_adma_free_chan_resources(struct dma_chan *chan)
{
        struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
        struct iop_adma_desc_slot *iter, *_iter;
        int in_use_descs = 0;

        iop_adma_slot_cleanup(iop_chan);

        spin_lock_bh(&iop_chan->lock);
        list_for_each_entry_safe(iter, _iter, &iop_chan->chain,
                                        chain_node) {
                in_use_descs++;
                list_del(&iter->chain_node);
        }
        list_for_each_entry_safe_reverse(
                iter, _iter, &iop_chan->all_slots, slot_node) {
                list_del(&iter->slot_node);
                kfree(iter);
                iop_chan->slots_allocated--;
        }
        iop_chan->last_used = NULL;

        dev_dbg(iop_chan->device->common.dev, "%s slots_allocated %d\n",
                __func__, iop_chan->slots_allocated);
        spin_unlock_bh(&iop_chan->lock);

        /* one is ok since we left it on there on purpose */
        if (in_use_descs > 1)
                printk(KERN_ERR "IOP: Freeing %d in use descriptors!\n",
                        in_use_descs - 1);
}

/**
 * iop_adma_is_complete - poll the status of an ADMA transaction
 * @chan: ADMA channel handle
 * @cookie: ADMA transaction identifier
 */
static enum dma_status iop_adma_is_complete(struct dma_chan *chan,
                                        dma_cookie_t cookie,
                                        dma_cookie_t *done,
                                        dma_cookie_t *used)
{
        struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
        dma_cookie_t last_used;
        dma_cookie_t last_complete;
        enum dma_status ret;

        last_used = chan->cookie;
        last_complete = iop_chan->completed_cookie;

        if (done)
                *done = last_complete;
        if (used)
                *used = last_used;

        ret = dma_async_is_complete(cookie, last_complete, last_used);
        if (ret == DMA_SUCCESS)
                return ret;

        iop_adma_slot_cleanup(iop_chan);

        last_used = chan->cookie;
        last_complete = iop_chan->completed_cookie;

        if (done)
                *done = last_complete;
        if (used)
                *used = last_used;

        return dma_async_is_complete(cookie, last_complete, last_used);
}

static irqreturn_t iop_adma_eot_handler(int irq, void *data)
{
        struct iop_adma_chan *chan = data;

        dev_dbg(chan->device->common.dev, "%s\n", __func__);

        tasklet_schedule(&chan->irq_tasklet);

        iop_adma_device_clear_eot_status(chan);

        return IRQ_HANDLED;
}

static irqreturn_t iop_adma_eoc_handler(int irq, void *data)
{
        struct iop_adma_chan *chan = data;

        dev_dbg(chan->device->common.dev, "%s\n", __func__);

        tasklet_schedule(&chan->irq_tasklet);

        iop_adma_device_clear_eoc_status(chan);

        return IRQ_HANDLED;
}

static irqreturn_t iop_adma_err_handler(int irq, void *data)
{
        struct iop_adma_chan *chan = data;
        unsigned long status = iop_chan_get_status(chan);

        dev_printk(KERN_ERR, chan->device->common.dev,
                "error ( %s%s%s%s%s%s%s)\n",
                iop_is_err_int_parity(status, chan) ? "int_parity " : "",
                iop_is_err_mcu_abort(status, chan) ? "mcu_abort " : "",
                iop_is_err_int_tabort(status, chan) ? "int_tabort " : "",
                iop_is_err_int_mabort(status, chan) ? "int_mabort " : "",
                iop_is_err_pci_tabort(status, chan) ? "pci_tabort " : "",
                iop_is_err_pci_mabort(status, chan) ? "pci_mabort " : "",
                iop_is_err_split_tx(status, chan) ? "split_tx " : "");

        iop_adma_device_clear_err_status(chan);

        BUG();

        return IRQ_HANDLED;
}

static void iop_adma_issue_pending(struct dma_chan *chan)
{
        struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);

        if (iop_chan->pending) {
                iop_chan->pending = 0;
                iop_chan_append(iop_chan);
        }
}

/*
 * Perform a transaction to verify the HW works.
 */
#define IOP_ADMA_TEST_SIZE 2000

static int __devinit iop_adma_memcpy_self_test(struct iop_adma_device *device)
{
        int i;
        void *src, *dest;
        dma_addr_t src_dma, dest_dma;
        struct dma_chan *dma_chan;
        dma_cookie_t cookie;
        struct dma_async_tx_descriptor *tx;
        int err = 0;
        struct iop_adma_chan *iop_chan;

        dev_dbg(device->common.dev, "%s\n", __func__);

        src = kmalloc(IOP_ADMA_TEST_SIZE, GFP_KERNEL);
        if (!src)
                return -ENOMEM;
        dest = kzalloc(IOP_ADMA_TEST_SIZE, GFP_KERNEL);
        if (!dest) {
                kfree(src);
                return -ENOMEM;
        }

        /* Fill in src buffer */
        for (i = 0; i < IOP_ADMA_TEST_SIZE; i++)
                ((u8 *) src)[i] = (u8)i;

        /* Start copy, using first DMA channel */
        dma_chan = container_of(device->common.channels.next,
                                struct dma_chan,
                                device_node);
        if (iop_adma_alloc_chan_resources(dma_chan, NULL) < 1) {
                err = -ENODEV;
                goto out;
        }

        dest_dma = dma_map_single(dma_chan->device->dev, dest,
                                IOP_ADMA_TEST_SIZE, DMA_FROM_DEVICE);
        src_dma = dma_map_single(dma_chan->device->dev, src,
                                IOP_ADMA_TEST_SIZE, DMA_TO_DEVICE);
        tx = iop_adma_prep_dma_memcpy(dma_chan, dest_dma, src_dma,
                                      IOP_ADMA_TEST_SIZE,
                                      DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

        cookie = iop_adma_tx_submit(tx);
        iop_adma_issue_pending(dma_chan);
        msleep(1);

        if (iop_adma_is_complete(dma_chan, cookie, NULL, NULL) !=
                        DMA_SUCCESS) {
                dev_printk(KERN_ERR, dma_chan->device->dev,
                        "Self-test copy timed out, disabling\n");
                err = -ENODEV;
                goto free_resources;
        }

        iop_chan = to_iop_adma_chan(dma_chan);
        dma_sync_single_for_cpu(&iop_chan->device->pdev->dev, dest_dma,
                IOP_ADMA_TEST_SIZE, DMA_FROM_DEVICE);
        if (memcmp(src, dest, IOP_ADMA_TEST_SIZE)) {
                dev_printk(KERN_ERR, dma_chan->device->dev,
                        "Self-test copy failed compare, disabling\n");
                err = -ENODEV;
                goto free_resources;
        }

free_resources:
        iop_adma_free_chan_resources(dma_chan);
out:
        kfree(src);
        kfree(dest);
        return err;
}

#define IOP_ADMA_NUM_SRC_TEST 4 /* must be <= 15 */
static int __devinit
iop_adma_xor_zero_sum_self_test(struct iop_adma_device *device)
{
        int i, src_idx;
        struct page *dest;
        struct page *xor_srcs[IOP_ADMA_NUM_SRC_TEST];
        struct page *zero_sum_srcs[IOP_ADMA_NUM_SRC_TEST + 1];
        dma_addr_t dma_srcs[IOP_ADMA_NUM_SRC_TEST + 1];
        dma_addr_t dma_addr, dest_dma;
        struct dma_async_tx_descriptor *tx;
        struct dma_chan *dma_chan;
        dma_cookie_t cookie;
        u8 cmp_byte = 0;
        u32 cmp_word;
        u32 zero_sum_result;
        int err = 0;
        struct iop_adma_chan *iop_chan;

        dev_dbg(device->common.dev, "%s\n", __func__);

        for (src_idx = 0; src_idx < IOP_ADMA_NUM_SRC_TEST; src_idx++) {
                xor_srcs[src_idx] = alloc_page(GFP_KERNEL);
                if (!xor_srcs[src_idx])
                        while (src_idx--) {
                                __free_page(xor_srcs[src_idx]);
                                return -ENOMEM;
                        }
        }

        dest = alloc_page(GFP_KERNEL);
        if (!dest)
                while (src_idx--) {
                        __free_page(xor_srcs[src_idx]);
                        return -ENOMEM;
                }

        /* Fill in src buffers */
        for (src_idx = 0; src_idx < IOP_ADMA_NUM_SRC_TEST; src_idx++) {
                u8 *ptr = page_address(xor_srcs[src_idx]);
                for (i = 0; i < PAGE_SIZE; i++)
                        ptr[i] = (1 << src_idx);
        }

        for (src_idx = 0; src_idx < IOP_ADMA_NUM_SRC_TEST; src_idx++)
                cmp_byte ^= (u8) (1 << src_idx);

        cmp_word = (cmp_byte << 24) | (cmp_byte << 16) |
                        (cmp_byte << 8) | cmp_byte;

        memset(page_address(dest), 0, PAGE_SIZE);

        dma_chan = container_of(device->common.channels.next,
                                struct dma_chan,
                                device_node);
        if (iop_adma_alloc_chan_resources(dma_chan, NULL) < 1) {
                err = -ENODEV;
                goto out;
        }

        /* test xor */
        dest_dma = dma_map_page(dma_chan->device->dev, dest, 0,
                                PAGE_SIZE, DMA_FROM_DEVICE);
        for (i = 0; i < IOP_ADMA_NUM_SRC_TEST; i++)
                dma_srcs[i] = dma_map_page(dma_chan->device->dev, xor_srcs[i],
                                           0, PAGE_SIZE, DMA_TO_DEVICE);
        tx = iop_adma_prep_dma_xor(dma_chan, dest_dma, dma_srcs,
                                   IOP_ADMA_NUM_SRC_TEST, PAGE_SIZE,
                                   DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

        cookie = iop_adma_tx_submit(tx);
        iop_adma_issue_pending(dma_chan);
        msleep(8);

        if (iop_adma_is_complete(dma_chan, cookie, NULL, NULL) !=
                DMA_SUCCESS) {
                dev_printk(KERN_ERR, dma_chan->device->dev,
                        "Self-test xor timed out, disabling\n");
                err = -ENODEV;
                goto free_resources;
        }

        iop_chan = to_iop_adma_chan(dma_chan);
        dma_sync_single_for_cpu(&iop_chan->device->pdev->dev, dest_dma,
                PAGE_SIZE, DMA_FROM_DEVICE);
        for (i = 0; i < (PAGE_SIZE / sizeof(u32)); i++) {
                u32 *ptr = page_address(dest);
                if (ptr[i] != cmp_word) {
                        dev_printk(KERN_ERR, dma_chan->device->dev,
                                "Self-test xor failed compare, disabling\n");
                        err = -ENODEV;
                        goto free_resources;
                }
        }
        dma_sync_single_for_device(&iop_chan->device->pdev->dev, dest_dma,
                PAGE_SIZE, DMA_TO_DEVICE);

        /* skip zero sum if the capability is not present */
        if (!dma_has_cap(DMA_ZERO_SUM, dma_chan->device->cap_mask))
                goto free_resources;

        /* zero sum the sources with the destintation page */
        for (i = 0; i < IOP_ADMA_NUM_SRC_TEST; i++)
                zero_sum_srcs[i] = xor_srcs[i];
        zero_sum_srcs[i] = dest;

        zero_sum_result = 1;

        for (i = 0; i < IOP_ADMA_NUM_SRC_TEST + 1; i++)
                dma_srcs[i] = dma_map_page(dma_chan->device->dev,
                                           zero_sum_srcs[i], 0, PAGE_SIZE,
                                           DMA_TO_DEVICE);
        tx = iop_adma_prep_dma_zero_sum(dma_chan, dma_srcs,
                                        IOP_ADMA_NUM_SRC_TEST + 1, PAGE_SIZE,
                                        &zero_sum_result,
                                        DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

        cookie = iop_adma_tx_submit(tx);
        iop_adma_issue_pending(dma_chan);
        msleep(8);

        if (iop_adma_is_complete(dma_chan, cookie, NULL, NULL) != DMA_SUCCESS) {
                dev_printk(KERN_ERR, dma_chan->device->dev,
                        "Self-test zero sum timed out, disabling\n");
                err = -ENODEV;
                goto free_resources;
        }

        if (zero_sum_result != 0) {
                dev_printk(KERN_ERR, dma_chan->device->dev,
                        "Self-test zero sum failed compare, disabling\n");
                err = -ENODEV;
                goto free_resources;
        }

        /* test memset */
        dma_addr = dma_map_page(dma_chan->device->dev, dest, 0,
                        PAGE_SIZE, DMA_FROM_DEVICE);
        tx = iop_adma_prep_dma_memset(dma_chan, dma_addr, 0, PAGE_SIZE,
                                      DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

        cookie = iop_adma_tx_submit(tx);
        iop_adma_issue_pending(dma_chan);
        msleep(8);

        if (iop_adma_is_complete(dma_chan, cookie, NULL, NULL) != DMA_SUCCESS) {
                dev_printk(KERN_ERR, dma_chan->device->dev,
                        "Self-test memset timed out, disabling\n");
                err = -ENODEV;
                goto free_resources;
        }

        for (i = 0; i < PAGE_SIZE/sizeof(u32); i++) {
                u32 *ptr = page_address(dest);
                if (ptr[i]) {
                        dev_printk(KERN_ERR, dma_chan->device->dev,
                                "Self-test memset failed compare, disabling\n");
                        err = -ENODEV;
                        goto free_resources;
                }
        }

        /* test for non-zero parity sum */
        zero_sum_result = 0;
        for (i = 0; i < IOP_ADMA_NUM_SRC_TEST + 1; i++)
                dma_srcs[i] = dma_map_page(dma_chan->device->dev,
                                           zero_sum_srcs[i], 0, PAGE_SIZE,
                                           DMA_TO_DEVICE);
        tx = iop_adma_prep_dma_zero_sum(dma_chan, dma_srcs,
                                        IOP_ADMA_NUM_SRC_TEST + 1, PAGE_SIZE,
                                        &zero_sum_result,
                                        DMA_PREP_INTERRUPT | DMA_CTRL_ACK);

        cookie = iop_adma_tx_submit(tx);
        iop_adma_issue_pending(dma_chan);
        msleep(8);

        if (iop_adma_is_complete(dma_chan, cookie, NULL, NULL) != DMA_SUCCESS) {
                dev_printk(KERN_ERR, dma_chan->device->dev,
                        "Self-test non-zero sum timed out, disabling\n");
                err = -ENODEV;
                goto free_resources;
        }

        if (zero_sum_result != 1) {
                dev_printk(KERN_ERR, dma_chan->device->dev,
                        "Self-test non-zero sum failed compare, disabling\n");
                err = -ENODEV;
                goto free_resources;
        }

free_resources:
        iop_adma_free_chan_resources(dma_chan);
out:
        src_idx = IOP_ADMA_NUM_SRC_TEST;
        while (src_idx--)
                __free_page(xor_srcs[src_idx]);
        __free_page(dest);
        return err;
}

static int __devexit iop_adma_remove(struct platform_device *dev)
{
        struct iop_adma_device *device = platform_get_drvdata(dev);
        struct dma_chan *chan, *_chan;
        struct iop_adma_chan *iop_chan;
        int i;
        struct iop_adma_platform_data *plat_data = dev->dev.platform_data;

        dma_async_device_unregister(&device->common);

        for (i = 0; i < 3; i++) {
                unsigned int irq;
                irq = platform_get_irq(dev, i);
                free_irq(irq, device);
        }

        dma_free_coherent(&dev->dev, plat_data->pool_size,
                        device->dma_desc_pool_virt, device->dma_desc_pool);

        do {
                struct resource *res;
                res = platform_get_resource(dev, IORESOURCE_MEM, 0);
                release_mem_region(res->start, res->end - res->start);
        } while (0);

        list_for_each_entry_safe(chan, _chan, &device->common.channels,
                                device_node) {
                iop_chan = to_iop_adma_chan(chan);
                list_del(&chan->device_node);
                kfree(iop_chan);
        }
        kfree(device);

        return 0;
}

static int __devinit iop_adma_probe(struct platform_device *pdev)
{
        struct resource *res;
        int ret = 0, i;
        struct iop_adma_device *adev;
        struct iop_adma_chan *iop_chan;
        struct dma_device *dma_dev;
        struct iop_adma_platform_data *plat_data = pdev->dev.platform_data;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res)
                return -ENODEV;

        if (!devm_request_mem_region(&pdev->dev, res->start,
                                res->end - res->start, pdev->name))
                return -EBUSY;

        adev = kzalloc(sizeof(*adev), GFP_KERNEL);
        if (!adev)
                return -ENOMEM;
        dma_dev = &adev->common;

        /* allocate coherent memory for hardware descriptors
         * note: writecombine gives slightly better performance, but
         * requires that we explicitly flush the writes
         */
        if ((adev->dma_desc_pool_virt = dma_alloc_writecombine(&pdev->dev,
                                        plat_data->pool_size,
                                        &adev->dma_desc_pool,
                                        GFP_KERNEL)) == NULL) {
                ret = -ENOMEM;
                goto err_free_adev;
        }

        dev_dbg(&pdev->dev, "%s: allocted descriptor pool virt %p phys %p\n",
                __func__, adev->dma_desc_pool_virt,
                (void *) adev->dma_desc_pool);

        adev->id = plat_data->hw_id;

        /* discover transaction capabilites from the platform data */
        dma_dev->cap_mask = plat_data->cap_mask;

        adev->pdev = pdev;
        platform_set_drvdata(pdev, adev);

        INIT_LIST_HEAD(&dma_dev->channels);

        /* set base routines */
        dma_dev->device_alloc_chan_resources = iop_adma_alloc_chan_resources;
        dma_dev->device_free_chan_resources = iop_adma_free_chan_resources;
        dma_dev->device_is_tx_complete = iop_adma_is_complete;
        dma_dev->device_issue_pending = iop_adma_issue_pending;
        dma_dev->dev = &pdev->dev;

        /* set prep routines based on capability */
        if (dma_has_cap(DMA_MEMCPY, dma_dev->cap_mask))
                dma_dev->device_prep_dma_memcpy = iop_adma_prep_dma_memcpy;
        if (dma_has_cap(DMA_MEMSET, dma_dev->cap_mask))
                dma_dev->device_prep_dma_memset = iop_adma_prep_dma_memset;
        if (dma_has_cap(DMA_XOR, dma_dev->cap_mask)) {
                dma_dev->max_xor = iop_adma_get_max_xor();
                dma_dev->device_prep_dma_xor = iop_adma_prep_dma_xor;
        }
        if (dma_has_cap(DMA_ZERO_SUM, dma_dev->cap_mask))
                dma_dev->device_prep_dma_zero_sum =
                        iop_adma_prep_dma_zero_sum;
        if (dma_has_cap(DMA_INTERRUPT, dma_dev->cap_mask))
                dma_dev->device_prep_dma_interrupt =
                        iop_adma_prep_dma_interrupt;

        iop_chan = kzalloc(sizeof(*iop_chan), GFP_KERNEL);
        if (!iop_chan) {
                ret = -ENOMEM;
                goto err_free_dma;
        }
        iop_chan->device = adev;

        iop_chan->mmr_base = devm_ioremap(&pdev->dev, res->start,
                                        res->end - res->start);
        if (!iop_chan->mmr_base) {
                ret = -ENOMEM;
                goto err_free_iop_chan;
        }
        tasklet_init(&iop_chan->irq_tasklet, iop_adma_tasklet, (unsigned long)
                iop_chan);

        /* clear errors before enabling interrupts */
        iop_adma_device_clear_err_status(iop_chan);

        for (i = 0; i < 3; i++) {
                irq_handler_t handler[] = { iop_adma_eot_handler,
                                        iop_adma_eoc_handler,
                                        iop_adma_err_handler };
                int irq = platform_get_irq(pdev, i);
                if (irq < 0) {
                        ret = -ENXIO;
                        goto err_free_iop_chan;
                } else {
                        ret = devm_request_irq(&pdev->dev, irq,
                                        handler[i], 0, pdev->name, iop_chan);
                        if (ret)
                                goto err_free_iop_chan;
                }
        }

        spin_lock_init(&iop_chan->lock);
        INIT_LIST_HEAD(&iop_chan->chain);
        INIT_LIST_HEAD(&iop_chan->all_slots);
        INIT_RCU_HEAD(&iop_chan->common.rcu);
        iop_chan->common.device = dma_dev;
        list_add_tail(&iop_chan->common.device_node, &dma_dev->channels);

        if (dma_has_cap(DMA_MEMCPY, dma_dev->cap_mask)) {
                ret = iop_adma_memcpy_self_test(adev);
                dev_dbg(&pdev->dev, "memcpy self test returned %d\n", ret);
                if (ret)
                        goto err_free_iop_chan;
        }

        if (dma_has_cap(DMA_XOR, dma_dev->cap_mask) ||
                dma_has_cap(DMA_MEMSET, dma_dev->cap_mask)) {
                ret = iop_adma_xor_zero_sum_self_test(adev);
                dev_dbg(&pdev->dev, "xor self test returned %d\n", ret);
                if (ret)
                        goto err_free_iop_chan;
        }

        dev_printk(KERN_INFO, &pdev->dev, "Intel(R) IOP: "
          "( %s%s%s%s%s%s%s%s%s%s)\n",
          dma_has_cap(DMA_PQ_XOR, dma_dev->cap_mask) ? "pq_xor " : "",
          dma_has_cap(DMA_PQ_UPDATE, dma_dev->cap_mask) ? "pq_update " : "",
          dma_has_cap(DMA_PQ_ZERO_SUM, dma_dev->cap_mask) ? "pq_zero_sum " : "",
          dma_has_cap(DMA_XOR, dma_dev->cap_mask) ? "xor " : "",
          dma_has_cap(DMA_DUAL_XOR, dma_dev->cap_mask) ? "dual_xor " : "",
          dma_has_cap(DMA_ZERO_SUM, dma_dev->cap_mask) ? "xor_zero_sum " : "",
          dma_has_cap(DMA_MEMSET, dma_dev->cap_mask)  ? "fill " : "",
          dma_has_cap(DMA_MEMCPY_CRC32C, dma_dev->cap_mask) ? "cpy+crc " : "",
          dma_has_cap(DMA_MEMCPY, dma_dev->cap_mask) ? "cpy " : "",
          dma_has_cap(DMA_INTERRUPT, dma_dev->cap_mask) ? "intr " : "");

        dma_async_device_register(dma_dev);
        goto out;

 err_free_iop_chan:
        kfree(iop_chan);
 err_free_dma:
        dma_free_coherent(&adev->pdev->dev, plat_data->pool_size,
                        adev->dma_desc_pool_virt, adev->dma_desc_pool);
 err_free_adev:
        kfree(adev);
 out:
        return ret;
}

static void iop_chan_start_null_memcpy(struct iop_adma_chan *iop_chan)
{
        struct iop_adma_desc_slot *sw_desc, *grp_start;
        dma_cookie_t cookie;
        int slot_cnt, slots_per_op;

        dev_dbg(iop_chan->device->common.dev, "%s\n", __func__);

        spin_lock_bh(&iop_chan->lock);
        slot_cnt = iop_chan_memcpy_slot_count(0, &slots_per_op);
        sw_desc = iop_adma_alloc_slots(iop_chan, slot_cnt, slots_per_op);
        if (sw_desc) {
                grp_start = sw_desc->group_head;

                list_splice_init(&sw_desc->async_tx.tx_list, &iop_chan->chain);
                async_tx_ack(&sw_desc->async_tx);
                iop_desc_init_memcpy(grp_start, 0);
                iop_desc_set_byte_count(grp_start, iop_chan, 0);
                iop_desc_set_dest_addr(grp_start, iop_chan, 0);
                iop_desc_set_memcpy_src_addr(grp_start, 0);

                cookie = iop_chan->common.cookie;
                cookie++;
                if (cookie <= 1)
                        cookie = 2;

                /* initialize the completed cookie to be less than
                 * the most recently used cookie
                 */
                iop_chan->completed_cookie = cookie - 1;
                iop_chan->common.cookie = sw_desc->async_tx.cookie = cookie;

                /* channel should not be busy */
                BUG_ON(iop_chan_is_busy(iop_chan));

                /* clear any prior error-status bits */
                iop_adma_device_clear_err_status(iop_chan);

                /* disable operation */
                iop_chan_disable(iop_chan);

                /* set the descriptor address */
                iop_chan_set_next_descriptor(iop_chan, sw_desc->async_tx.phys);

                /* 1/ don't add pre-chained descriptors
                 * 2/ dummy read to flush next_desc write
                 */
                BUG_ON(iop_desc_get_next_desc(sw_desc));

                /* run the descriptor */
                iop_chan_enable(iop_chan);
        } else
                dev_printk(KERN_ERR, iop_chan->device->common.dev,
                         "failed to allocate null descriptor\n");
        spin_unlock_bh(&iop_chan->lock);
}

static void iop_chan_start_null_xor(struct iop_adma_chan *iop_chan)
{
        struct iop_adma_desc_slot *sw_desc, *grp_start;
        dma_cookie_t cookie;
        int slot_cnt, slots_per_op;

        dev_dbg(iop_chan->device->common.dev, "%s\n", __func__);

        spin_lock_bh(&iop_chan->lock);
        slot_cnt = iop_chan_xor_slot_count(0, 2, &slots_per_op);
        sw_desc = iop_adma_alloc_slots(iop_chan, slot_cnt, slots_per_op);
        if (sw_desc) {
                grp_start = sw_desc->group_head;
                list_splice_init(&sw_desc->async_tx.tx_list, &iop_chan->chain);
                async_tx_ack(&sw_desc->async_tx);
                iop_desc_init_null_xor(grp_start, 2, 0);
                iop_desc_set_byte_count(grp_start, iop_chan, 0);
                iop_desc_set_dest_addr(grp_start, iop_chan, 0);
                iop_desc_set_xor_src_addr(grp_start, 0, 0);
                iop_desc_set_xor_src_addr(grp_start, 1, 0);

                cookie = iop_chan->common.cookie;
                cookie++;
                if (cookie <= 1)
                        cookie = 2;

                /* initialize the completed cookie to be less than
                 * the most recently used cookie
                 */
                iop_chan->completed_cookie = cookie - 1;
                iop_chan->common.cookie = sw_desc->async_tx.cookie = cookie;

                /* channel should not be busy */
                BUG_ON(iop_chan_is_busy(iop_chan));

                /* clear any prior error-status bits */
                iop_adma_device_clear_err_status(iop_chan);

                /* disable operation */
                iop_chan_disable(iop_chan);

                /* set the descriptor address */
                iop_chan_set_next_descriptor(iop_chan, sw_desc->async_tx.phys);

                /* 1/ don't add pre-chained descriptors
                 * 2/ dummy read to flush next_desc write
                 */
                BUG_ON(iop_desc_get_next_desc(sw_desc));

                /* run the descriptor */
                iop_chan_enable(iop_chan);
        } else
                dev_printk(KERN_ERR, iop_chan->device->common.dev,
                        "failed to allocate null descriptor\n");
        spin_unlock_bh(&iop_chan->lock);
}

MODULE_ALIAS("platform:iop-adma");

static struct platform_driver iop_adma_driver = {
        .probe          = iop_adma_probe,
        .remove         = iop_adma_remove,
        .driver         = {
                .owner  = THIS_MODULE,
                .name   = "iop-adma",
        },
};

static int __init iop_adma_init (void)
{
        return platform_driver_register(&iop_adma_driver);
}

/* it's currently unsafe to unload this module */
#if 0
static void __exit iop_adma_exit (void)
{
        platform_driver_unregister(&iop_adma_driver);
        return;
}
module_exit(iop_adma_exit);
#endif

module_init(iop_adma_init);

MODULE_AUTHOR("Intel Corporation");
MODULE_DESCRIPTION("IOP ADMA Engine Driver");
MODULE_LICENSE("GPL");