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>

1 files changed, 35 insertions, 82 deletions

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;