ioat1: trim ioat_dma_desc_sw

Save 4 bytes per software descriptor by transmitting tx_cnt in an unused
portion of the hardware descriptor.

Signed-off-by: Maciej Sosnowski <maciej.sosnowski@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

3 files changed, 7 insertions, 5 deletions

diff --git a/drivers/dma/ioat/dma.c b/drivers/dma/ioat/dma.c
index abc96c4c0796..f59b6f42f866 100644
--- a/drivers/dma/ioat/dma.c
+++ b/drivers/dma/ioat/dma.c
@@ -396,7 +396,7 @@ static dma_cookie_t ioat1_tx_submit(struct dma_async_tx_descriptor *tx)
         dump_desc_dbg(ioat, chain_tail);
         dump_desc_dbg(ioat, first);
 
-        ioat->pending += desc->tx_cnt;
+        ioat->pending += desc->hw->tx_cnt;
         if (ioat->pending >= ioat_pending_level)
                 __ioat1_dma_memcpy_issue_pending(ioat);
         spin_unlock_bh(&ioat->desc_lock);
@@ -655,11 +655,11 @@ ioat1_dma_prep_memcpy(struct dma_chan *c, dma_addr_t dma_dest,
         spin_unlock_bh(&ioat->desc_lock);
 
         desc->txd.flags = flags;
-        desc->tx_cnt = tx_cnt;
         desc->len = total_len;
         list_splice(&chain, &desc->txd.tx_list);
         hw->ctl_f.int_en = !!(flags & DMA_PREP_INTERRUPT);
         hw->ctl_f.compl_write = 1;
+        hw->tx_cnt = tx_cnt;
         dump_desc_dbg(ioat, desc);
 
         return &desc->txd;
diff --git a/drivers/dma/ioat/dma.h b/drivers/dma/ioat/dma.h
index e47083b52ee7..ec851cf5345c 100644
--- a/drivers/dma/ioat/dma.h
+++ b/drivers/dma/ioat/dma.h
@@ -165,14 +165,12 @@ ioat_is_complete(struct dma_chan *c, dma_cookie_t cookie,
  * @hw: hardware DMA descriptor
  * @node: this descriptor will either be on the free list,
  *     or attached to a transaction list (async_tx.tx_list)
- * @tx_cnt: number of descriptors required to complete the transaction
  * @txd: the generic software descriptor for all engines
  * @id: identifier for debug
  */
 struct ioat_desc_sw {
         struct ioat_dma_descriptor *hw;
         struct list_head node;
-        int tx_cnt;
         size_t len;
         struct dma_async_tx_descriptor txd;
         #ifdef DEBUG
diff --git a/drivers/dma/ioat/hw.h b/drivers/dma/ioat/hw.h
index e13f3ed47763..7481fb13ce00 100644
--- a/drivers/dma/ioat/hw.h
+++ b/drivers/dma/ioat/hw.h
@@ -63,7 +63,11 @@ struct ioat_dma_descriptor {
         uint64_t        next;
         uint64_t        rsv1;
         uint64_t        rsv2;
-        uint64_t        user1;
+        /* store some driver data in an unused portion of the descriptor */
+        union {
+                uint64_t        user1;
+                uint64_t        tx_cnt;
+        };
         uint64_t        user2;
 };
 #endif