ioat2,3: dynamically resize descriptor ring

[linux-2.6/btrfs-unstable.git] / drivers / dma / ioat / dma_v2.c

/*
 * Intel I/OAT DMA Linux driver
 * Copyright(c) 2004 - 2009 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 that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * The full GNU General Public License is included in this distribution in
 * the file called "COPYING".
 *
 */

/*
 * This driver supports an Intel I/OAT DMA engine (versions >= 2), which
 * does asynchronous data movement and checksumming operations.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/interrupt.h>
#include <linux/dmaengine.h>
#include <linux/delay.h>
#include <linux/dma-mapping.h>
#include <linux/workqueue.h>
#include <linux/i7300_idle.h>
#include "dma.h"
#include "dma_v2.h"
#include "registers.h"
#include "hw.h"

static int ioat_ring_alloc_order = 8;
module_param(ioat_ring_alloc_order, int, 0644);
MODULE_PARM_DESC(ioat_ring_alloc_order,
                 "ioat2+: allocate 2^n descriptors per channel (default: n=8)");
static int ioat_ring_max_alloc_order = IOAT_MAX_ORDER;
module_param(ioat_ring_max_alloc_order, int, 0644);
MODULE_PARM_DESC(ioat_ring_max_alloc_order,
                 "ioat2+: upper limit for dynamic ring resizing (default: n=16)");

static void __ioat2_issue_pending(struct ioat2_dma_chan *ioat)
{
        void * __iomem reg_base = ioat->base.reg_base;

        ioat->pending = 0;
        ioat->dmacount += ioat2_ring_pending(ioat);;
        ioat->issued = ioat->head;
        /* make descriptor updates globally visible before notifying channel */
        wmb();
        writew(ioat->dmacount, reg_base + IOAT_CHAN_DMACOUNT_OFFSET);
        dev_dbg(to_dev(&ioat->base),
                "%s: head: %#x tail: %#x issued: %#x count: %#x\n",
                __func__, ioat->head, ioat->tail, ioat->issued, ioat->dmacount);
}

static void ioat2_issue_pending(struct dma_chan *chan)
{
        struct ioat2_dma_chan *ioat = to_ioat2_chan(chan);

        spin_lock_bh(&ioat->ring_lock);
        if (ioat->pending == 1)
                __ioat2_issue_pending(ioat);
        spin_unlock_bh(&ioat->ring_lock);
}

/**
 * ioat2_update_pending - log pending descriptors
 * @ioat: ioat2+ channel
 *
 * set pending to '1' unless pending is already set to '2', pending == 2
 * indicates that submission is temporarily blocked due to an in-flight
 * reset.  If we are already above the ioat_pending_level threshold then
 * just issue pending.
 *
 * called with ring_lock held
 */
static void ioat2_update_pending(struct ioat2_dma_chan *ioat)
{
        if (unlikely(ioat->pending == 2))
                return;
        else if (ioat2_ring_pending(ioat) > ioat_pending_level)
                __ioat2_issue_pending(ioat);
        else
                ioat->pending = 1;
}

static void __ioat2_start_null_desc(struct ioat2_dma_chan *ioat)
{
        struct ioat_ring_ent *desc;
        struct ioat_dma_descriptor *hw;
        int idx;

        if (ioat2_ring_space(ioat) < 1) {
                dev_err(to_dev(&ioat->base),
                        "Unable to start null desc - ring full\n");
                return;
        }

        dev_dbg(to_dev(&ioat->base), "%s: head: %#x tail: %#x issued: %#x\n",
                __func__, ioat->head, ioat->tail, ioat->issued);
        idx = ioat2_desc_alloc(ioat, 1);
        desc = ioat2_get_ring_ent(ioat, idx);

        hw = desc->hw;
        hw->ctl = 0;
        hw->ctl_f.null = 1;
        hw->ctl_f.int_en = 1;
        hw->ctl_f.compl_write = 1;
        /* set size to non-zero value (channel returns error when size is 0) */
        hw->size = NULL_DESC_BUFFER_SIZE;
        hw->src_addr = 0;
        hw->dst_addr = 0;
        async_tx_ack(&desc->txd);
        ioat2_set_chainaddr(ioat, desc->txd.phys);
        dump_desc_dbg(ioat, desc);
        __ioat2_issue_pending(ioat);
}

static void ioat2_start_null_desc(struct ioat2_dma_chan *ioat)
{
        spin_lock_bh(&ioat->ring_lock);
        __ioat2_start_null_desc(ioat);
        spin_unlock_bh(&ioat->ring_lock);
}

static void __cleanup(struct ioat2_dma_chan *ioat, unsigned long phys_complete)
{
        struct ioat_chan_common *chan = &ioat->base;
        struct dma_async_tx_descriptor *tx;
        struct ioat_ring_ent *desc;
        bool seen_current = false;
        u16 active;
        int i;

        dev_dbg(to_dev(chan), "%s: head: %#x tail: %#x issued: %#x\n",
                __func__, ioat->head, ioat->tail, ioat->issued);

        active = ioat2_ring_active(ioat);
        for (i = 0; i < active && !seen_current; i++) {
                prefetch(ioat2_get_ring_ent(ioat, ioat->tail + i + 1));
                desc = ioat2_get_ring_ent(ioat, ioat->tail + i);
                tx = &desc->txd;
                dump_desc_dbg(ioat, desc);
                if (tx->cookie) {
                        ioat_dma_unmap(chan, tx->flags, desc->len, desc->hw);
                        chan->completed_cookie = tx->cookie;
                        tx->cookie = 0;
                        if (tx->callback) {
                                tx->callback(tx->callback_param);
                                tx->callback = NULL;
                        }
                }

                if (tx->phys == phys_complete)
                        seen_current = true;
        }
        ioat->tail += i;
        BUG_ON(!seen_current); /* no active descs have written a completion? */

        chan->last_completion = phys_complete;
        if (ioat->head == ioat->tail) {
                dev_dbg(to_dev(chan), "%s: cancel completion timeout\n",
                        __func__);
                clear_bit(IOAT_COMPLETION_PENDING, &chan->state);
                mod_timer(&chan->timer, jiffies + IDLE_TIMEOUT);
        }
}

/**
 * ioat2_cleanup - clean finished descriptors (advance tail pointer)
 * @chan: ioat channel to be cleaned up
 */
static void ioat2_cleanup(struct ioat2_dma_chan *ioat)
{
        struct ioat_chan_common *chan = &ioat->base;
        unsigned long phys_complete;

        prefetch(chan->completion);

        if (!spin_trylock_bh(&chan->cleanup_lock))
                return;

        if (!ioat_cleanup_preamble(chan, &phys_complete)) {
                spin_unlock_bh(&chan->cleanup_lock);
                return;
        }

        if (!spin_trylock_bh(&ioat->ring_lock)) {
                spin_unlock_bh(&chan->cleanup_lock);
                return;
        }

        __cleanup(ioat, phys_complete);

        spin_unlock_bh(&ioat->ring_lock);
        spin_unlock_bh(&chan->cleanup_lock);
}

static void ioat2_cleanup_tasklet(unsigned long data)
{
        struct ioat2_dma_chan *ioat = (void *) data;

        ioat2_cleanup(ioat);
        writew(IOAT_CHANCTRL_RUN, ioat->base.reg_base + IOAT_CHANCTRL_OFFSET);
}

static void __restart_chan(struct ioat2_dma_chan *ioat)
{
        struct ioat_chan_common *chan = &ioat->base;

        /* set the tail to be re-issued */
        ioat->issued = ioat->tail;
        ioat->dmacount = 0;
        set_bit(IOAT_COMPLETION_PENDING, &chan->state);
        mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);

        dev_dbg(to_dev(chan),
                "%s: head: %#x tail: %#x issued: %#x count: %#x\n",
                __func__, ioat->head, ioat->tail, ioat->issued, ioat->dmacount);

        if (ioat2_ring_pending(ioat)) {
                struct ioat_ring_ent *desc;

                desc = ioat2_get_ring_ent(ioat, ioat->tail);
                ioat2_set_chainaddr(ioat, desc->txd.phys);
                __ioat2_issue_pending(ioat);
        } else
                __ioat2_start_null_desc(ioat);
}

static void ioat2_restart_channel(struct ioat2_dma_chan *ioat)
{
        struct ioat_chan_common *chan = &ioat->base;
        unsigned long phys_complete;
        u32 status;

        status = ioat_chansts(chan);
        if (is_ioat_active(status) || is_ioat_idle(status))
                ioat_suspend(chan);
        while (is_ioat_active(status) || is_ioat_idle(status)) {
                status = ioat_chansts(chan);
                cpu_relax();
        }

        if (ioat_cleanup_preamble(chan, &phys_complete))
                __cleanup(ioat, phys_complete);

        __restart_chan(ioat);
}

static bool reshape_ring(struct ioat2_dma_chan *ioat, int order);

static void ioat2_timer_event(unsigned long data)
{
        struct ioat2_dma_chan *ioat = (void *) data;
        struct ioat_chan_common *chan = &ioat->base;

        spin_lock_bh(&chan->cleanup_lock);
        if (test_bit(IOAT_COMPLETION_PENDING, &chan->state)) {
                unsigned long phys_complete;
                u64 status;

                spin_lock_bh(&ioat->ring_lock);
                status = ioat_chansts(chan);

                /* when halted due to errors check for channel
                 * programming errors before advancing the completion state
                 */
                if (is_ioat_halted(status)) {
                        u32 chanerr;

                        chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
                        BUG_ON(is_ioat_bug(chanerr));
                }

                /* if we haven't made progress and we have already
                 * acknowledged a pending completion once, then be more
                 * forceful with a restart
                 */
                if (ioat_cleanup_preamble(chan, &phys_complete))
                        __cleanup(ioat, phys_complete);
                else if (test_bit(IOAT_COMPLETION_ACK, &chan->state))
                        ioat2_restart_channel(ioat);
                else {
                        set_bit(IOAT_COMPLETION_ACK, &chan->state);
                        mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
                }
                spin_unlock_bh(&ioat->ring_lock);
        } else {
                u16 active;

                /* if the ring is idle, empty, and oversized try to step
                 * down the size
                 */
                spin_lock_bh(&ioat->ring_lock);
                active = ioat2_ring_active(ioat);
                if (active == 0 && ioat->alloc_order > ioat_get_alloc_order())
                        reshape_ring(ioat, ioat->alloc_order-1);
                spin_unlock_bh(&ioat->ring_lock);

                /* keep shrinking until we get back to our minimum
                 * default size
                 */
                if (ioat->alloc_order > ioat_get_alloc_order())
                        mod_timer(&chan->timer, jiffies + IDLE_TIMEOUT);
        }
        spin_unlock_bh(&chan->cleanup_lock);
}

/**
 * ioat2_enumerate_channels - find and initialize the device's channels
 * @device: the device to be enumerated
 */
static int ioat2_enumerate_channels(struct ioatdma_device *device)
{
        struct ioat2_dma_chan *ioat;
        struct device *dev = &device->pdev->dev;
        struct dma_device *dma = &device->common;
        u8 xfercap_log;
        int i;

        INIT_LIST_HEAD(&dma->channels);
        dma->chancnt = readb(device->reg_base + IOAT_CHANCNT_OFFSET);
        dma->chancnt &= 0x1f; /* bits [4:0] valid */
        if (dma->chancnt > ARRAY_SIZE(device->idx)) {
                dev_warn(dev, "(%d) exceeds max supported channels (%zu)\n",
                         dma->chancnt, ARRAY_SIZE(device->idx));
                dma->chancnt = ARRAY_SIZE(device->idx);
        }
        xfercap_log = readb(device->reg_base + IOAT_XFERCAP_OFFSET);
        xfercap_log &= 0x1f; /* bits [4:0] valid */
        if (xfercap_log == 0)
                return 0;
        dev_dbg(dev, "%s: xfercap = %d\n", __func__, 1 << xfercap_log);

        /* FIXME which i/oat version is i7300? */
#ifdef CONFIG_I7300_IDLE_IOAT_CHANNEL
        if (i7300_idle_platform_probe(NULL, NULL, 1) == 0)
                dma->chancnt--;
#endif
        for (i = 0; i < dma->chancnt; i++) {
                ioat = devm_kzalloc(dev, sizeof(*ioat), GFP_KERNEL);
                if (!ioat)
                        break;

                ioat_init_channel(device, &ioat->base, i,
                                  ioat2_timer_event,
                                  ioat2_cleanup_tasklet,
                                  (unsigned long) ioat);
                ioat->xfercap_log = xfercap_log;
                spin_lock_init(&ioat->ring_lock);
        }
        dma->chancnt = i;
        return i;
}

static dma_cookie_t ioat2_tx_submit_unlock(struct dma_async_tx_descriptor *tx)
{
        struct dma_chan *c = tx->chan;
        struct ioat2_dma_chan *ioat = to_ioat2_chan(c);
        struct ioat_chan_common *chan = &ioat->base;
        dma_cookie_t cookie = c->cookie;

        cookie++;
        if (cookie < 0)
                cookie = 1;
        tx->cookie = cookie;
        c->cookie = cookie;
        dev_dbg(to_dev(&ioat->base), "%s: cookie: %d\n", __func__, cookie);

        if (!test_and_set_bit(IOAT_COMPLETION_PENDING, &chan->state))
                mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
        ioat2_update_pending(ioat);
        spin_unlock_bh(&ioat->ring_lock);

        return cookie;
}

static struct ioat_ring_ent *ioat2_alloc_ring_ent(struct dma_chan *chan, gfp_t flags)
{
        struct ioat_dma_descriptor *hw;
        struct ioat_ring_ent *desc;
        struct ioatdma_device *dma;
        dma_addr_t phys;

        dma = to_ioatdma_device(chan->device);
        hw = pci_pool_alloc(dma->dma_pool, flags, &phys);
        if (!hw)
                return NULL;
        memset(hw, 0, sizeof(*hw));

        desc = kzalloc(sizeof(*desc), flags);
        if (!desc) {
                pci_pool_free(dma->dma_pool, hw, phys);
                return NULL;
        }

        dma_async_tx_descriptor_init(&desc->txd, chan);
        desc->txd.tx_submit = ioat2_tx_submit_unlock;
        desc->hw = hw;
        desc->txd.phys = phys;
        return desc;
}

static void ioat2_free_ring_ent(struct ioat_ring_ent *desc, struct dma_chan *chan)
{
        struct ioatdma_device *dma;

        dma = to_ioatdma_device(chan->device);
        pci_pool_free(dma->dma_pool, desc->hw, desc->txd.phys);
        kfree(desc);
}

static struct ioat_ring_ent **ioat2_alloc_ring(struct dma_chan *c, int order, gfp_t flags)
{
        struct ioat_ring_ent **ring;
        int descs = 1 << order;
        int i;

        if (order > ioat_get_max_alloc_order())
                return NULL;

        /* allocate the array to hold the software ring */
        ring = kcalloc(descs, sizeof(*ring), flags);
        if (!ring)
                return NULL;
        for (i = 0; i < descs; i++) {
                ring[i] = ioat2_alloc_ring_ent(c, flags);
                if (!ring[i]) {
                        while (i--)
                                ioat2_free_ring_ent(ring[i], c);
                        kfree(ring);
                        return NULL;
                }
                set_desc_id(ring[i], i);
        }

        /* link descs */
        for (i = 0; i < descs-1; i++) {
                struct ioat_ring_ent *next = ring[i+1];
                struct ioat_dma_descriptor *hw = ring[i]->hw;

                hw->next = next->txd.phys;
        }
        ring[i]->hw->next = ring[0]->txd.phys;

        return ring;
}

/* ioat2_alloc_chan_resources - allocate/initialize ioat2 descriptor ring
 * @chan: channel to be initialized
 */
static int ioat2_alloc_chan_resources(struct dma_chan *c)
{
        struct ioat2_dma_chan *ioat = to_ioat2_chan(c);
        struct ioat_chan_common *chan = &ioat->base;
        struct ioat_ring_ent **ring;
        u32 chanerr;
        int order;

        /* have we already been set up? */
        if (ioat->ring)
                return 1 << ioat->alloc_order;

        /* Setup register to interrupt and write completion status on error */
        writew(IOAT_CHANCTRL_RUN, chan->reg_base + IOAT_CHANCTRL_OFFSET);

        chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
        if (chanerr) {
                dev_err(to_dev(chan), "CHANERR = %x, clearing\n", chanerr);
                writel(chanerr, chan->reg_base + IOAT_CHANERR_OFFSET);
        }

        /* allocate a completion writeback area */
        /* doing 2 32bit writes to mmio since 1 64b write doesn't work */
        chan->completion = pci_pool_alloc(chan->device->completion_pool,
                                          GFP_KERNEL, &chan->completion_dma);
        if (!chan->completion)
                return -ENOMEM;

        memset(chan->completion, 0, sizeof(*chan->completion));
        writel(((u64) chan->completion_dma) & 0x00000000FFFFFFFF,
               chan->reg_base + IOAT_CHANCMP_OFFSET_LOW);
        writel(((u64) chan->completion_dma) >> 32,
               chan->reg_base + IOAT_CHANCMP_OFFSET_HIGH);

        order = ioat_get_alloc_order();
        ring = ioat2_alloc_ring(c, order, GFP_KERNEL);
        if (!ring)
                return -ENOMEM;

        spin_lock_bh(&ioat->ring_lock);
        ioat->ring = ring;
        ioat->head = 0;
        ioat->issued = 0;
        ioat->tail = 0;
        ioat->pending = 0;
        ioat->alloc_order = order;
        spin_unlock_bh(&ioat->ring_lock);

        tasklet_enable(&chan->cleanup_task);
        ioat2_start_null_desc(ioat);

        return 1 << ioat->alloc_order;
}

static bool reshape_ring(struct ioat2_dma_chan *ioat, int order)
{
        /* reshape differs from normal ring allocation in that we want
         * to allocate a new software ring while only
         * extending/truncating the hardware ring
         */
        struct ioat_chan_common *chan = &ioat->base;
        struct dma_chan *c = &chan->common;
        const u16 curr_size = ioat2_ring_mask(ioat) + 1;
        const u16 active = ioat2_ring_active(ioat);
        const u16 new_size = 1 << order;
        struct ioat_ring_ent **ring;
        u16 i;

        if (order > ioat_get_max_alloc_order())
                return false;

        /* double check that we have at least 1 free descriptor */
        if (active == curr_size)
                return false;

        /* when shrinking, verify that we can hold the current active
         * set in the new ring
         */
        if (active >= new_size)
                return false;

        /* allocate the array to hold the software ring */
        ring = kcalloc(new_size, sizeof(*ring), GFP_NOWAIT);
        if (!ring)
                return false;

        /* allocate/trim descriptors as needed */
        if (new_size > curr_size) {
                /* copy current descriptors to the new ring */
                for (i = 0; i < curr_size; i++) {
                        u16 curr_idx = (ioat->tail+i) & (curr_size-1);
                        u16 new_idx = (ioat->tail+i) & (new_size-1);

                        ring[new_idx] = ioat->ring[curr_idx];
                        set_desc_id(ring[new_idx], new_idx);
                }

                /* add new descriptors to the ring */
                for (i = curr_size; i < new_size; i++) {
                        u16 new_idx = (ioat->tail+i) & (new_size-1);

                        ring[new_idx] = ioat2_alloc_ring_ent(c, GFP_NOWAIT);
                        if (!ring[new_idx]) {
                                while (i--) {
                                        u16 new_idx = (ioat->tail+i) & (new_size-1);

                                        ioat2_free_ring_ent(ring[new_idx], c);
                                }
                                kfree(ring);
                                return false;
                        }
                        set_desc_id(ring[new_idx], new_idx);
                }

                /* hw link new descriptors */
                for (i = curr_size-1; i < new_size; i++) {
                        u16 new_idx = (ioat->tail+i) & (new_size-1);
                        struct ioat_ring_ent *next = ring[(new_idx+1) & (new_size-1)];
                        struct ioat_dma_descriptor *hw = ring[new_idx]->hw;

                        hw->next = next->txd.phys;
                }
        } else {
                struct ioat_dma_descriptor *hw;
                struct ioat_ring_ent *next;

                /* copy current descriptors to the new ring, dropping the
                 * removed descriptors
                 */
                for (i = 0; i < new_size; i++) {
                        u16 curr_idx = (ioat->tail+i) & (curr_size-1);
                        u16 new_idx = (ioat->tail+i) & (new_size-1);

                        ring[new_idx] = ioat->ring[curr_idx];
                        set_desc_id(ring[new_idx], new_idx);
                }

                /* free deleted descriptors */
                for (i = new_size; i < curr_size; i++) {
                        struct ioat_ring_ent *ent;

                        ent = ioat2_get_ring_ent(ioat, ioat->tail+i);
                        ioat2_free_ring_ent(ent, c);
                }

                /* fix up hardware ring */
                hw = ring[(ioat->tail+new_size-1) & (new_size-1)]->hw;
                next = ring[(ioat->tail+new_size) & (new_size-1)];
                hw->next = next->txd.phys;
        }

        dev_dbg(to_dev(chan), "%s: allocated %d descriptors\n",
                __func__, new_size);

        kfree(ioat->ring);
        ioat->ring = ring;
        ioat->alloc_order = order;

        return true;
}

/**
 * ioat2_alloc_and_lock - common descriptor alloc boilerplate for ioat2,3 ops
 * @idx: gets starting descriptor index on successful allocation
 * @ioat: ioat2,3 channel (ring) to operate on
 * @num_descs: allocation length
 */
static int ioat2_alloc_and_lock(u16 *idx, struct ioat2_dma_chan *ioat, int num_descs)
{
        struct ioat_chan_common *chan = &ioat->base;

        spin_lock_bh(&ioat->ring_lock);
        /* never allow the last descriptor to be consumed, we need at
         * least one free at all times to allow for on-the-fly ring
         * resizing.
         */
        while (unlikely(ioat2_ring_space(ioat) <= num_descs)) {
                if (reshape_ring(ioat, ioat->alloc_order + 1) &&
                    ioat2_ring_space(ioat) > num_descs)
                                break;

                if (printk_ratelimit())
                        dev_dbg(to_dev(chan),
                                "%s: ring full! num_descs: %d (%x:%x:%x)\n",
                                __func__, num_descs, ioat->head, ioat->tail,
                                ioat->issued);
                spin_unlock_bh(&ioat->ring_lock);

                /* progress reclaim in the allocation failure case we
                 * may be called under bh_disabled so we need to trigger
                 * the timer event directly
                 */
                spin_lock_bh(&chan->cleanup_lock);
                if (jiffies > chan->timer.expires &&
                    timer_pending(&chan->timer)) {
                        mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
                        spin_unlock_bh(&chan->cleanup_lock);
                        ioat2_timer_event((unsigned long) ioat);
                } else
                        spin_unlock_bh(&chan->cleanup_lock);
                return -ENOMEM;
        }

        dev_dbg(to_dev(chan), "%s: num_descs: %d (%x:%x:%x)\n",
                __func__, num_descs, ioat->head, ioat->tail, ioat->issued);

        *idx = ioat2_desc_alloc(ioat, num_descs);
        return 0;  /* with ioat->ring_lock held */
}

static struct dma_async_tx_descriptor *
ioat2_dma_prep_memcpy_lock(struct dma_chan *c, dma_addr_t dma_dest,
                           dma_addr_t dma_src, size_t len, unsigned long flags)
{
        struct ioat2_dma_chan *ioat = to_ioat2_chan(c);
        struct ioat_dma_descriptor *hw;
        struct ioat_ring_ent *desc;
        dma_addr_t dst = dma_dest;
        dma_addr_t src = dma_src;
        size_t total_len = len;
        int num_descs;
        u16 idx;
        int i;

        num_descs = ioat2_xferlen_to_descs(ioat, len);
        if (likely(num_descs) &&
            ioat2_alloc_and_lock(&idx, ioat, num_descs) == 0)
                /* pass */;
        else
                return NULL;
        for (i = 0; i < num_descs; i++) {
                size_t copy = min_t(size_t, len, 1 << ioat->xfercap_log);

                desc = ioat2_get_ring_ent(ioat, idx + i);
                hw = desc->hw;

                hw->size = copy;
                hw->ctl = 0;
                hw->src_addr = src;
                hw->dst_addr = dst;

                len -= copy;
                dst += copy;
                src += copy;
                dump_desc_dbg(ioat, desc);
        }

        desc->txd.flags = flags;
        desc->len = total_len;
        hw->ctl_f.int_en = !!(flags & DMA_PREP_INTERRUPT);
        hw->ctl_f.compl_write = 1;
        dump_desc_dbg(ioat, desc);
        /* we leave the channel locked to ensure in order submission */

        return &desc->txd;
}

/**
 * ioat2_free_chan_resources - release all the descriptors
 * @chan: the channel to be cleaned
 */
static void ioat2_free_chan_resources(struct dma_chan *c)
{
        struct ioat2_dma_chan *ioat = to_ioat2_chan(c);
        struct ioat_chan_common *chan = &ioat->base;
        struct ioatdma_device *ioatdma_device = chan->device;
        struct ioat_ring_ent *desc;
        const u16 total_descs = 1 << ioat->alloc_order;
        int descs;
        int i;

        /* Before freeing channel resources first check
         * if they have been previously allocated for this channel.
         */
        if (!ioat->ring)
                return;

        tasklet_disable(&chan->cleanup_task);
        del_timer_sync(&chan->timer);
        ioat2_cleanup(ioat);

        /* Delay 100ms after reset to allow internal DMA logic to quiesce
         * before removing DMA descriptor resources.
         */
        writeb(IOAT_CHANCMD_RESET,
               chan->reg_base + IOAT_CHANCMD_OFFSET(chan->device->version));
        mdelay(100);

        spin_lock_bh(&ioat->ring_lock);
        descs = ioat2_ring_space(ioat);
        dev_dbg(to_dev(chan), "freeing %d idle descriptors\n", descs);
        for (i = 0; i < descs; i++) {
                desc = ioat2_get_ring_ent(ioat, ioat->head + i);
                ioat2_free_ring_ent(desc, c);
        }

        if (descs < total_descs)
                dev_err(to_dev(chan), "Freeing %d in use descriptors!\n",
                        total_descs - descs);

        for (i = 0; i < total_descs - descs; i++) {
                desc = ioat2_get_ring_ent(ioat, ioat->tail + i);
                dump_desc_dbg(ioat, desc);
                ioat2_free_ring_ent(desc, c);
        }

        kfree(ioat->ring);
        ioat->ring = NULL;
        ioat->alloc_order = 0;
        pci_pool_free(ioatdma_device->completion_pool,
                      chan->completion,
                      chan->completion_dma);
        spin_unlock_bh(&ioat->ring_lock);

        chan->last_completion = 0;
        chan->completion_dma = 0;
        ioat->pending = 0;
        ioat->dmacount = 0;
}

static enum dma_status
ioat2_is_complete(struct dma_chan *c, dma_cookie_t cookie,
                     dma_cookie_t *done, dma_cookie_t *used)
{
        struct ioat2_dma_chan *ioat = to_ioat2_chan(c);

        if (ioat_is_complete(c, cookie, done, used) == DMA_SUCCESS)
                return DMA_SUCCESS;

        ioat2_cleanup(ioat);

        return ioat_is_complete(c, cookie, done, used);
}

int __devinit ioat2_dma_probe(struct ioatdma_device *device, int dca)
{
        struct pci_dev *pdev = device->pdev;
        struct dma_device *dma;
        struct dma_chan *c;
        struct ioat_chan_common *chan;
        int err;

        device->enumerate_channels = ioat2_enumerate_channels;
        dma = &device->common;
        dma->device_prep_dma_memcpy = ioat2_dma_prep_memcpy_lock;
        dma->device_issue_pending = ioat2_issue_pending;
        dma->device_alloc_chan_resources = ioat2_alloc_chan_resources;
        dma->device_free_chan_resources = ioat2_free_chan_resources;
        dma->device_is_tx_complete = ioat2_is_complete;

        err = ioat_probe(device);
        if (err)
                return err;
        ioat_set_tcp_copy_break(2048);

        list_for_each_entry(c, &dma->channels, device_node) {
                chan = to_chan_common(c);
                writel(IOAT_DCACTRL_CMPL_WRITE_ENABLE | IOAT_DMA_DCA_ANY_CPU,
                       chan->reg_base + IOAT_DCACTRL_OFFSET);
        }

        err = ioat_register(device);
        if (err)
                return err;
        if (dca)
                device->dca = ioat2_dca_init(pdev, device->reg_base);

        return err;
}

int __devinit ioat3_dma_probe(struct ioatdma_device *device, int dca)
{
        struct pci_dev *pdev = device->pdev;
        struct dma_device *dma;
        struct dma_chan *c;
        struct ioat_chan_common *chan;
        int err;
        u16 dev_id;

        device->enumerate_channels = ioat2_enumerate_channels;
        dma = &device->common;
        dma->device_prep_dma_memcpy = ioat2_dma_prep_memcpy_lock;
        dma->device_issue_pending = ioat2_issue_pending;
        dma->device_alloc_chan_resources = ioat2_alloc_chan_resources;
        dma->device_free_chan_resources = ioat2_free_chan_resources;
        dma->device_is_tx_complete = ioat2_is_complete;

        /* -= IOAT ver.3 workarounds =- */
        /* Write CHANERRMSK_INT with 3E07h to mask out the errors
         * that can cause stability issues for IOAT ver.3
         */
        pci_write_config_dword(pdev, IOAT_PCI_CHANERRMASK_INT_OFFSET, 0x3e07);

        /* Clear DMAUNCERRSTS Cfg-Reg Parity Error status bit
         * (workaround for spurious config parity error after restart)
         */
        pci_read_config_word(pdev, IOAT_PCI_DEVICE_ID_OFFSET, &dev_id);
        if (dev_id == PCI_DEVICE_ID_INTEL_IOAT_TBG0)
                pci_write_config_dword(pdev, IOAT_PCI_DMAUNCERRSTS_OFFSET, 0x10);

        err = ioat_probe(device);
        if (err)
                return err;
        ioat_set_tcp_copy_break(262144);

        list_for_each_entry(c, &dma->channels, device_node) {
                chan = to_chan_common(c);
                writel(IOAT_DMA_DCA_ANY_CPU,
                       chan->reg_base + IOAT_DCACTRL_OFFSET);
        }

        err = ioat_register(device);
        if (err)
                return err;
        if (dca)
                device->dca = ioat3_dca_init(pdev, device->reg_base);

        return err;
}