ioat2,3: convert to producer/consumer locking

Use separate locks for the descriptor prep (producer) and descriptor
cleanup (consumer) paths.  Allows the producer path to run concurrently
with the cleanup path.  Inspired by Documentation/circular-buffer.txt.

Cc: David Howells <dhowells@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

4 files changed, 134 insertions, 181 deletions

diff --git a/drivers/dma/ioat/dma.h b/drivers/dma/ioat/dma.h
index 86b97ac8774e..0c76578e9911 100644
--- a/drivers/dma/ioat/dma.h
+++ b/drivers/dma/ioat/dma.h
@@ -96,6 +96,7 @@ struct ioat_chan_common {
         #define IOAT_COMPLETION_ACK 1
         #define IOAT_RESET_PENDING 2
         #define IOAT_KOBJ_INIT_FAIL 3
+        #define IOAT_RESHAPE_PENDING 4
         struct timer_list timer;
         #define COMPLETION_TIMEOUT msecs_to_jiffies(100)
         #define IDLE_TIMEOUT msecs_to_jiffies(2000)
diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
index b6699a350989..e75d0299bb82 100644
--- a/drivers/dma/ioat/dma_v2.c
+++ b/drivers/dma/ioat/dma_v2.c
@@ -56,8 +56,6 @@ void __ioat2_issue_pending(struct ioat2_dma_chan *ioat)
 
         ioat->dmacount += ioat2_ring_pending(ioat);
         ioat->issued = ioat->head;
-        /* make descriptor updates globally visible before notifying channel */
-        wmb();
         writew(ioat->dmacount, chan->reg_base + IOAT_CHAN_DMACOUNT_OFFSET);
         dev_dbg(to_dev(chan),
                 "%s: head: %#x tail: %#x issued: %#x count: %#x\n",
@@ -69,9 +67,9 @@ void ioat2_issue_pending(struct dma_chan *c)
         struct ioat2_dma_chan *ioat = to_ioat2_chan(c);
 
         if (ioat2_ring_pending(ioat)) {
-                spin_lock_bh(&ioat->ring_lock);
+                spin_lock_bh(&ioat->prep_lock);
                 __ioat2_issue_pending(ioat);
-                spin_unlock_bh(&ioat->ring_lock);
+                spin_unlock_bh(&ioat->prep_lock);
         }
 }
 
@@ -80,7 +78,7 @@ void ioat2_issue_pending(struct dma_chan *c)
  * @ioat: ioat2+ channel
  *
  * Check if the number of unsubmitted descriptors has exceeded the
- * watermark.  Called with ring_lock held
+ * watermark.  Called with prep_lock held
  */
 static void ioat2_update_pending(struct ioat2_dma_chan *ioat)
 {
@@ -92,7 +90,6 @@ 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),
@@ -102,8 +99,7 @@ static void __ioat2_start_null_desc(struct ioat2_dma_chan *ioat)
 
         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);
+        desc = ioat2_get_ring_ent(ioat, ioat->head);
 
         hw = desc->hw;
         hw->ctl = 0;
@@ -117,14 +113,16 @@ static void __ioat2_start_null_desc(struct ioat2_dma_chan *ioat)
         async_tx_ack(&desc->txd);
         ioat2_set_chainaddr(ioat, desc->txd.phys);
         dump_desc_dbg(ioat, desc);
+        wmb();
+        ioat->head += 1;
         __ioat2_issue_pending(ioat);
 }
 
 static void ioat2_start_null_desc(struct ioat2_dma_chan *ioat)
 {
-        spin_lock_bh(&ioat->ring_lock);
+        spin_lock_bh(&ioat->prep_lock);
         __ioat2_start_null_desc(ioat);
-        spin_unlock_bh(&ioat->ring_lock);
+        spin_unlock_bh(&ioat->prep_lock);
 }
 
 static void __cleanup(struct ioat2_dma_chan *ioat, unsigned long phys_complete)
@@ -134,15 +132,16 @@ static void __cleanup(struct ioat2_dma_chan *ioat, unsigned long phys_complete)
         struct ioat_ring_ent *desc;
         bool seen_current = false;
         u16 active;
-        int i;
+        int idx = ioat->tail, 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);
+                smp_read_barrier_depends();
+                prefetch(ioat2_get_ring_ent(ioat, idx + i + 1));
+                desc = ioat2_get_ring_ent(ioat, idx + i);
                 tx = &desc->txd;
                 dump_desc_dbg(ioat, desc);
                 if (tx->cookie) {
@@ -158,11 +157,12 @@ static void __cleanup(struct ioat2_dma_chan *ioat, unsigned long phys_complete)
                 if (tx->phys == phys_complete)
                         seen_current = true;
         }
-        ioat->tail += i;
+        smp_mb(); /* finish all descriptor reads before incrementing tail */
+        ioat->tail = idx + i;
         BUG_ON(active && !seen_current); /* no active descs have written a completion? */
 
         chan->last_completion = phys_complete;
-        if (ioat->head == ioat->tail) {
+        if (active - i == 0) {
                 dev_dbg(to_dev(chan), "%s: cancel completion timeout\n",
                         __func__);
                 clear_bit(IOAT_COMPLETION_PENDING, &chan->state);
@@ -179,24 +179,9 @@ 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_lock_bh(&chan->cleanup_lock);
+        if (ioat_cleanup_preamble(chan, &phys_complete))
+                __cleanup(ioat, phys_complete);
         spin_unlock_bh(&chan->cleanup_lock);
 }
 
@@ -287,12 +272,10 @@ void ioat2_timer_event(unsigned long data)
         struct ioat2_dma_chan *ioat = to_ioat2_chan((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
@@ -311,26 +294,31 @@ void ioat2_timer_event(unsigned long data)
                  * acknowledged a pending completion once, then be more
                  * forceful with a restart
                  */
-                if (ioat_cleanup_preamble(chan, &phys_complete))
+                spin_lock_bh(&chan->cleanup_lock);
+                if (ioat_cleanup_preamble(chan, &phys_complete)) {
                         __cleanup(ioat, phys_complete);
-                else if (test_bit(IOAT_COMPLETION_ACK, &chan->state))
+                } else if (test_bit(IOAT_COMPLETION_ACK, &chan->state)) {
+                        spin_lock_bh(&ioat->prep_lock);
                         ioat2_restart_channel(ioat);
-                else {
+                        spin_unlock_bh(&ioat->prep_lock);
+                } else {
                         set_bit(IOAT_COMPLETION_ACK, &chan->state);
                         mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
                 }
-                spin_unlock_bh(&ioat->ring_lock);
+                spin_unlock_bh(&chan->cleanup_lock);
         } else {
                 u16 active;
 
                 /* if the ring is idle, empty, and oversized try to step
                  * down the size
                  */
-                spin_lock_bh(&ioat->ring_lock);
+                spin_lock_bh(&chan->cleanup_lock);
+                spin_lock_bh(&ioat->prep_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);
+                spin_unlock_bh(&ioat->prep_lock);
+                spin_unlock_bh(&chan->cleanup_lock);
 
                 /* keep shrinking until we get back to our minimum
                  * default size
@@ -338,7 +326,6 @@ void ioat2_timer_event(unsigned long data)
                 if (ioat->alloc_order > ioat_get_alloc_order())
                         mod_timer(&chan->timer, jiffies + IDLE_TIMEOUT);
         }
-        spin_unlock_bh(&chan->cleanup_lock);
 }
 
 static int ioat2_reset_hw(struct ioat_chan_common *chan)
@@ -392,7 +379,7 @@ int ioat2_enumerate_channels(struct ioatdma_device *device)
 
                 ioat_init_channel(device, &ioat->base, i);
                 ioat->xfercap_log = xfercap_log;
-                spin_lock_init(&ioat->ring_lock);
+                spin_lock_init(&ioat->prep_lock);
                 if (device->reset_hw(&ioat->base)) {
                         i = 0;
                         break;
@@ -418,8 +405,17 @@ static dma_cookie_t ioat2_tx_submit_unlock(struct dma_async_tx_descriptor *tx)
 
         if (!test_and_set_bit(IOAT_COMPLETION_PENDING, &chan->state))
                 mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+
+        /* make descriptor updates visible before advancing ioat->head,
+         * this is purposefully not smp_wmb() since we are also
+         * publishing the descriptor updates to a dma device
+         */
+        wmb();
+
+        ioat->head += ioat->produce;
+
         ioat2_update_pending(ioat);
-        spin_unlock_bh(&ioat->ring_lock);
+        spin_unlock_bh(&ioat->prep_lock);
 
         return cookie;
 }
@@ -531,13 +527,15 @@ int ioat2_alloc_chan_resources(struct dma_chan *c)
         if (!ring)
                 return -ENOMEM;
 
-        spin_lock_bh(&ioat->ring_lock);
+        spin_lock_bh(&chan->cleanup_lock);
+        spin_lock_bh(&ioat->prep_lock);
         ioat->ring = ring;
         ioat->head = 0;
         ioat->issued = 0;
         ioat->tail = 0;
         ioat->alloc_order = order;
-        spin_unlock_bh(&ioat->ring_lock);
+        spin_unlock_bh(&ioat->prep_lock);
+        spin_unlock_bh(&chan->cleanup_lock);
 
         tasklet_enable(&chan->cleanup_task);
         ioat2_start_null_desc(ioat);
@@ -653,54 +651,61 @@ bool reshape_ring(struct ioat2_dma_chan *ioat, int order)
 }
 
 /**
- * ioat2_alloc_and_lock - common descriptor alloc boilerplate for ioat2,3 ops
- * @idx: gets starting descriptor index on successful allocation
+ * ioat2_check_space_lock - verify space and grab ring producer lock
  * @ioat: ioat2,3 channel (ring) to operate on
  * @num_descs: allocation length
  */
-int ioat2_alloc_and_lock(u16 *idx, struct ioat2_dma_chan *ioat, int num_descs)
+int ioat2_check_space_lock(struct ioat2_dma_chan *ioat, int num_descs)
 {
         struct ioat_chan_common *chan = &ioat->base;
+        bool retry;
 
-        spin_lock_bh(&ioat->ring_lock);
+ retry:
+        spin_lock_bh(&ioat->prep_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)) {
-                        struct ioatdma_device *device = chan->device;
-
-                        mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
-                        spin_unlock_bh(&chan->cleanup_lock);
-                        device->timer_fn((unsigned long) &chan->common);
-                } else
-                        spin_unlock_bh(&chan->cleanup_lock);
-                return -ENOMEM;
+        if (likely(ioat2_ring_space(ioat) > num_descs)) {
+                dev_dbg(to_dev(chan), "%s: num_descs: %d (%x:%x:%x)\n",
+                        __func__, num_descs, ioat->head, ioat->tail, ioat->issued);
+                ioat->produce = num_descs;
+                return 0;  /* with ioat->prep_lock held */
         }
+        retry = test_and_set_bit(IOAT_RESHAPE_PENDING, &chan->state);
+        spin_unlock_bh(&ioat->prep_lock);
 
-        dev_dbg(to_dev(chan), "%s: num_descs: %d (%x:%x:%x)\n",
-                __func__, num_descs, ioat->head, ioat->tail, ioat->issued);
+        /* is another cpu already trying to expand the ring? */
+        if (retry)
+                goto retry;
 
-        *idx = ioat2_desc_alloc(ioat, num_descs);
-        return 0;  /* with ioat->ring_lock held */
+        spin_lock_bh(&chan->cleanup_lock);
+        spin_lock_bh(&ioat->prep_lock);
+        retry = reshape_ring(ioat, ioat->alloc_order + 1);
+        clear_bit(IOAT_RESHAPE_PENDING, &chan->state);
+        spin_unlock_bh(&ioat->prep_lock);
+        spin_unlock_bh(&chan->cleanup_lock);
+
+        /* if we were able to expand the ring retry the allocation */
+        if (retry)
+                goto retry;
+
+        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);
+
+        /* progress reclaim in the allocation failure case we may be
+         * called under bh_disabled so we need to trigger the timer
+         * event directly
+         */
+        if (jiffies > chan->timer.expires && timer_pending(&chan->timer)) {
+                struct ioatdma_device *device = chan->device;
+
+                mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
+                device->timer_fn((unsigned long) &chan->common);
+        }
+
+        return -ENOMEM;
 }
 
 struct dma_async_tx_descriptor *
@@ -713,14 +718,11 @@ ioat2_dma_prep_memcpy_lock(struct dma_chan *c, dma_addr_t dma_dest,
         dma_addr_t dst = dma_dest;
         dma_addr_t src = dma_src;
         size_t total_len = len;
-        int num_descs;
-        u16 idx;
-        int i;
+        int num_descs, idx, i;
 
         num_descs = ioat2_xferlen_to_descs(ioat, len);
-        if (likely(num_descs) &&
-            ioat2_alloc_and_lock(&idx, ioat, num_descs) == 0)
-                /* pass */;
+        if (likely(num_descs) && ioat2_check_space_lock(ioat, num_descs) == 0)
+                idx = ioat->head;
         else
                 return NULL;
         i = 0;
@@ -777,7 +779,8 @@ void ioat2_free_chan_resources(struct dma_chan *c)
         device->cleanup_fn((unsigned long) c);
         device->reset_hw(chan);
 
-        spin_lock_bh(&ioat->ring_lock);
+        spin_lock_bh(&chan->cleanup_lock);
+        spin_lock_bh(&ioat->prep_lock);
         descs = ioat2_ring_space(ioat);
         dev_dbg(to_dev(chan), "freeing %d idle descriptors\n", descs);
         for (i = 0; i < descs; i++) {
@@ -800,7 +803,8 @@ void ioat2_free_chan_resources(struct dma_chan *c)
         ioat->alloc_order = 0;
         pci_pool_free(device->completion_pool, chan->completion,
                       chan->completion_dma);
-        spin_unlock_bh(&ioat->ring_lock);
+        spin_unlock_bh(&ioat->prep_lock);
+        spin_unlock_bh(&chan->cleanup_lock);
 
         chan->last_completion = 0;
         chan->completion_dma = 0;
diff --git a/drivers/dma/ioat/dma_v2.h b/drivers/dma/ioat/dma_v2.h
index d7b64f188f78..a2c413b2b8d8 100644
--- a/drivers/dma/ioat/dma_v2.h
+++ b/drivers/dma/ioat/dma_v2.h
@@ -50,8 +50,9 @@ extern int ioat_ring_alloc_order;
  * @tail: cleanup index
  * @dmacount: identical to 'head' except for occasionally resetting to zero
  * @alloc_order: log2 of the number of allocated descriptors
+ * @produce: number of descriptors to produce at submit time
  * @ring: software ring buffer implementation of hardware ring
- * @ring_lock: protects ring attributes
+ * @prep_lock: serializes descriptor preparation (producers)
  */
 struct ioat2_dma_chan {
         struct ioat_chan_common base;
@@ -61,8 +62,9 @@ struct ioat2_dma_chan {
         u16 tail;
         u16 dmacount;
         u16 alloc_order;
+        u16 produce;
         struct ioat_ring_ent **ring;
-        spinlock_t ring_lock;
+        spinlock_t prep_lock;
 };
 
 static inline struct ioat2_dma_chan *to_ioat2_chan(struct dma_chan *c)
@@ -94,13 +96,6 @@ static inline u16 ioat2_ring_space(struct ioat2_dma_chan *ioat)
         return ioat2_ring_size(ioat) - ioat2_ring_active(ioat);
 }
 
-/* assumes caller already checked space */
-static inline u16 ioat2_desc_alloc(struct ioat2_dma_chan *ioat, u16 len)
-{
-        ioat->head += len;
-        return ioat->head - len;
-}
-
 static inline u16 ioat2_xferlen_to_descs(struct ioat2_dma_chan *ioat, size_t len)
 {
         u16 num_descs = len >> ioat->xfercap_log;
@@ -164,7 +159,7 @@ int __devinit ioat2_dma_probe(struct ioatdma_device *dev, int dca);
 int __devinit ioat3_dma_probe(struct ioatdma_device *dev, int dca);
 struct dca_provider * __devinit ioat2_dca_init(struct pci_dev *pdev, void __iomem *iobase);
 struct dca_provider * __devinit ioat3_dca_init(struct pci_dev *pdev, void __iomem *iobase);
-int ioat2_alloc_and_lock(u16 *idx, struct ioat2_dma_chan *ioat, int num_descs);
+int ioat2_check_space_lock(struct ioat2_dma_chan *ioat, int num_descs);
 int ioat2_enumerate_channels(struct ioatdma_device *device);
 struct dma_async_tx_descriptor *
 ioat2_dma_prep_memcpy_lock(struct dma_chan *c, dma_addr_t dma_dest,
diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
index 6740e319c9cf..8b573fac2a25 100644
--- a/drivers/dma/ioat/dma_v3.c
+++ b/drivers/dma/ioat/dma_v3.c
@@ -260,8 +260,8 @@ static void __cleanup(struct ioat2_dma_chan *ioat, unsigned long phys_complete)
         struct ioat_chan_common *chan = &ioat->base;
         struct ioat_ring_ent *desc;
         bool seen_current = false;
+        int idx = ioat->tail, i;
         u16 active;
-        int i;
 
         dev_dbg(to_dev(chan), "%s: head: %#x tail: %#x issued: %#x\n",
                 __func__, ioat->head, ioat->tail, ioat->issued);
@@ -270,13 +270,14 @@ static void __cleanup(struct ioat2_dma_chan *ioat, unsigned long phys_complete)
         for (i = 0; i < active && !seen_current; i++) {
                 struct dma_async_tx_descriptor *tx;
 
-                prefetch(ioat2_get_ring_ent(ioat, ioat->tail + i + 1));
-                desc = ioat2_get_ring_ent(ioat, ioat->tail + i);
+                smp_read_barrier_depends();
+                prefetch(ioat2_get_ring_ent(ioat, idx + i + 1));
+                desc = ioat2_get_ring_ent(ioat, idx + i);
                 dump_desc_dbg(ioat, desc);
                 tx = &desc->txd;
                 if (tx->cookie) {
                         chan->completed_cookie = tx->cookie;
-                        ioat3_dma_unmap(ioat, desc, ioat->tail + i);
+                        ioat3_dma_unmap(ioat, desc, idx + i);
                         tx->cookie = 0;
                         if (tx->callback) {
                                 tx->callback(tx->callback_param);
@@ -293,69 +294,30 @@ static void __cleanup(struct ioat2_dma_chan *ioat, unsigned long phys_complete)
                         i++;
                 }
         }
-        ioat->tail += i;
+        smp_mb(); /* finish all descriptor reads before incrementing tail */
+        ioat->tail = idx + i;
         BUG_ON(active && !seen_current); /* no active descs have written a completion? */
         chan->last_completion = phys_complete;
 
-        active = ioat2_ring_active(ioat);
-        if (active == 0) {
+        if (active - i == 0) {
                 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);
         }
         /* 5 microsecond delay per pending descriptor */
-        writew(min((5 * active), IOAT_INTRDELAY_MASK),
+        writew(min((5 * (active - i)), IOAT_INTRDELAY_MASK),
                chan->device->reg_base + IOAT_INTRDELAY_OFFSET);
 }
 
-/* try to cleanup, but yield (via spin_trylock) to incoming submissions
- * with the expectation that we will immediately poll again shortly
- */
-static void ioat3_cleanup_poll(struct ioat2_dma_chan *ioat)
+static void ioat3_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);
-}
-
-/* run cleanup now because we already delayed the interrupt via INTRDELAY */
-static void ioat3_cleanup_sync(struct ioat2_dma_chan *ioat)
-{
-        struct ioat_chan_common *chan = &ioat->base;
-        unsigned long phys_complete;
-
-        prefetch(chan->completion);
-
         spin_lock_bh(&chan->cleanup_lock);
-        if (!ioat_cleanup_preamble(chan, &phys_complete)) {
-                spin_unlock_bh(&chan->cleanup_lock);
-                return;
-        }
-        spin_lock_bh(&ioat->ring_lock);
-
-        __cleanup(ioat, phys_complete);
-
-        spin_unlock_bh(&ioat->ring_lock);
+        if (ioat_cleanup_preamble(chan, &phys_complete))
+                __cleanup(ioat, phys_complete);
         spin_unlock_bh(&chan->cleanup_lock);
 }
 
@@ -363,7 +325,7 @@ static void ioat3_cleanup_event(unsigned long data)
 {
         struct ioat2_dma_chan *ioat = to_ioat2_chan((void *) data);
 
-        ioat3_cleanup_sync(ioat);
+        ioat3_cleanup(ioat);
         writew(IOAT_CHANCTRL_RUN, ioat->base.reg_base + IOAT_CHANCTRL_OFFSET);
 }
 
@@ -384,12 +346,10 @@ static void ioat3_timer_event(unsigned long data)
         struct ioat2_dma_chan *ioat = to_ioat2_chan((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
@@ -408,26 +368,31 @@ static void ioat3_timer_event(unsigned long data)
                  * acknowledged a pending completion once, then be more
                  * forceful with a restart
                  */
+                spin_lock_bh(&chan->cleanup_lock);
                 if (ioat_cleanup_preamble(chan, &phys_complete))
                         __cleanup(ioat, phys_complete);
-                else if (test_bit(IOAT_COMPLETION_ACK, &chan->state))
+                else if (test_bit(IOAT_COMPLETION_ACK, &chan->state)) {
+                        spin_lock_bh(&ioat->prep_lock);
                         ioat3_restart_channel(ioat);
-                else {
+                        spin_unlock_bh(&ioat->prep_lock);
+                } else {
                         set_bit(IOAT_COMPLETION_ACK, &chan->state);
                         mod_timer(&chan->timer, jiffies + COMPLETION_TIMEOUT);
                 }
-                spin_unlock_bh(&ioat->ring_lock);
+                spin_unlock_bh(&chan->cleanup_lock);
         } else {
                 u16 active;
 
                 /* if the ring is idle, empty, and oversized try to step
                  * down the size
                  */
-                spin_lock_bh(&ioat->ring_lock);
+                spin_lock_bh(&chan->cleanup_lock);
+                spin_lock_bh(&ioat->prep_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);
+                spin_unlock_bh(&ioat->prep_lock);
+                spin_unlock_bh(&chan->cleanup_lock);
 
                 /* keep shrinking until we get back to our minimum
                  * default size
@@ -435,7 +400,6 @@ static void ioat3_timer_event(unsigned long data)
                 if (ioat->alloc_order > ioat_get_alloc_order())
                         mod_timer(&chan->timer, jiffies + IDLE_TIMEOUT);
         }
-        spin_unlock_bh(&chan->cleanup_lock);
 }
 
 static enum dma_status
@@ -447,7 +411,7 @@ ioat3_is_complete(struct dma_chan *c, dma_cookie_t cookie,
         if (ioat_is_complete(c, cookie, done, used) == DMA_SUCCESS)
                 return DMA_SUCCESS;
 
-        ioat3_cleanup_poll(ioat);
+        ioat3_cleanup(ioat);
 
         return ioat_is_complete(c, cookie, done, used);
 }
@@ -460,15 +424,12 @@ ioat3_prep_memset_lock(struct dma_chan *c, dma_addr_t dest, int value,
         struct ioat_ring_ent *desc;
         size_t total_len = len;
         struct ioat_fill_descriptor *fill;
-        int num_descs;
         u64 src_data = (0x0101010101010101ULL) * (value & 0xff);
-        u16 idx;
-        int i;
+        int num_descs, idx, i;
 
         num_descs = ioat2_xferlen_to_descs(ioat, len);
-        if (likely(num_descs) &&
-            ioat2_alloc_and_lock(&idx, ioat, num_descs) == 0)
-                /* pass */;
+        if (likely(num_descs) && ioat2_check_space_lock(ioat, num_descs) == 0)
+                idx = ioat->head;
         else
                 return NULL;
         i = 0;
@@ -513,11 +474,8 @@ __ioat3_prep_xor_lock(struct dma_chan *c, enum sum_check_flags *result,
         struct ioat_xor_descriptor *xor;
         struct ioat_xor_ext_descriptor *xor_ex = NULL;
         struct ioat_dma_descriptor *hw;
+        int num_descs, with_ext, idx, i;
         u32 offset = 0;
-        int num_descs;
-        int with_ext;
-        int i;
-        u16 idx;
         u8 op = result ? IOAT_OP_XOR_VAL : IOAT_OP_XOR;
 
         BUG_ON(src_cnt < 2);
@@ -537,9 +495,8 @@ __ioat3_prep_xor_lock(struct dma_chan *c, enum sum_check_flags *result,
          * (legacy) descriptor to ensure all completion writes arrive in
          * order.
          */
-        if (likely(num_descs) &&
-            ioat2_alloc_and_lock(&idx, ioat, num_descs+1) == 0)
-                /* pass */;
+        if (likely(num_descs) && ioat2_check_space_lock(ioat, num_descs+1) == 0)
+                idx = ioat->head;
         else
                 return NULL;
         i = 0;
@@ -657,11 +614,8 @@ __ioat3_prep_pq_lock(struct dma_chan *c, enum sum_check_flags *result,
         struct ioat_pq_ext_descriptor *pq_ex = NULL;
         struct ioat_dma_descriptor *hw;
         u32 offset = 0;
-        int num_descs;
-        int with_ext;
-        int i, s;
-        u16 idx;
         u8 op = result ? IOAT_OP_PQ_VAL : IOAT_OP_PQ;
+        int i, s, idx, with_ext, num_descs;
 
         dev_dbg(to_dev(chan), "%s\n", __func__);
         /* the engine requires at least two sources (we provide
@@ -687,8 +641,8 @@ __ioat3_prep_pq_lock(struct dma_chan *c, enum sum_check_flags *result,
          * order.
          */
         if (likely(num_descs) &&
-            ioat2_alloc_and_lock(&idx, ioat, num_descs+1) == 0)
-                /* pass */;
+            ioat2_check_space_lock(ioat, num_descs+1) == 0)
+                idx = ioat->head;
         else
                 return NULL;
         i = 0;
@@ -851,10 +805,9 @@ ioat3_prep_interrupt_lock(struct dma_chan *c, unsigned long flags)
         struct ioat2_dma_chan *ioat = to_ioat2_chan(c);
         struct ioat_ring_ent *desc;
         struct ioat_dma_descriptor *hw;
-        u16 idx;
 
-        if (ioat2_alloc_and_lock(&idx, ioat, 1) == 0)
-                desc = ioat2_get_ring_ent(ioat, idx);
+        if (ioat2_check_space_lock(ioat, 1) == 0)
+                desc = ioat2_get_ring_ent(ioat, ioat->head);
         else
                 return NULL;