async_tx: kill tx_set_src and tx_set_dest methods

The tx_set_src and tx_set_dest methods were originally implemented to allow
an array of addresses to be passed down from async_xor to the dmaengine
driver while minimizing stack overhead.  Removing these methods allows
drivers to have all transaction parameters available at 'prep' time, saves
two function pointers in struct dma_async_tx_descriptor, and reduces the
number of indirect branches..

A consequence of moving this data to the 'prep' routine is that
multi-source routines like async_xor need temporary storage to convert an
array of linear addresses into an array of dma addresses.  In order to keep
the same stack footprint of the previous implementation the input array is
reused as storage for the dma addresses.  This requires that
sizeof(dma_addr_t) be less than or equal to sizeof(void *).  As a
consequence CONFIG_DMADEVICES now depends on !CONFIG_HIGHMEM64G.  It also
requires that drivers be able to make descriptor resources available when
the 'prep' routine is polled.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Shannon Nelson <shannon.nelson@intel.com>

4 files changed, 87 insertions, 126 deletions

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index c46b7c219ee..a703deffb79 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -5,6 +5,7 @@
 menuconfig DMADEVICES
         bool "DMA Engine support"
         depends on (PCI && X86) || ARCH_IOP32X || ARCH_IOP33X || ARCH_IOP13XX
+        depends on !HIGHMEM64G
         help
           DMA engines can do asynchronous data transfers without
           involving the host CPU.  Currently, this framework can be
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index bcf52df3033..29965231b91 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -473,20 +473,22 @@ dma_async_memcpy_buf_to_buf(struct dma_chan *chan, void *dest,
 {
         struct dma_device *dev = chan->device;
         struct dma_async_tx_descriptor *tx;
-        dma_addr_t addr;
+        dma_addr_t dma_dest, dma_src;
         dma_cookie_t cookie;
         int cpu;
 
-        tx = dev->device_prep_dma_memcpy(chan, len, 0);
-        if (!tx)
+        dma_src = dma_map_single(dev->dev, src, len, DMA_TO_DEVICE);
+        dma_dest = dma_map_single(dev->dev, dest, len, DMA_FROM_DEVICE);
+        tx = dev->device_prep_dma_memcpy(chan, dma_dest, dma_src, len, 0);
+
+        if (!tx) {
+                dma_unmap_single(dev->dev, dma_src, len, DMA_TO_DEVICE);
+                dma_unmap_single(dev->dev, dma_dest, len, DMA_FROM_DEVICE);
                 return -ENOMEM;
+        }
 
         tx->ack = 1;
         tx->callback = NULL;
-        addr = dma_map_single(dev->dev, src, len, DMA_TO_DEVICE);
-        tx->tx_set_src(addr, tx, 0);
-        addr = dma_map_single(dev->dev, dest, len, DMA_FROM_DEVICE);
-        tx->tx_set_dest(addr, tx, 0);
         cookie = tx->tx_submit(tx);
 
         cpu = get_cpu();
@@ -517,20 +519,22 @@ dma_async_memcpy_buf_to_pg(struct dma_chan *chan, struct page *page,
 {
         struct dma_device *dev = chan->device;
         struct dma_async_tx_descriptor *tx;
-        dma_addr_t addr;
+        dma_addr_t dma_dest, dma_src;
         dma_cookie_t cookie;
         int cpu;
 
-        tx = dev->device_prep_dma_memcpy(chan, len, 0);
-        if (!tx)
+        dma_src = dma_map_single(dev->dev, kdata, len, DMA_TO_DEVICE);
+        dma_dest = dma_map_page(dev->dev, page, offset, len, DMA_FROM_DEVICE);
+        tx = dev->device_prep_dma_memcpy(chan, dma_dest, dma_src, len, 0);
+
+        if (!tx) {
+                dma_unmap_single(dev->dev, dma_src, len, DMA_TO_DEVICE);
+                dma_unmap_page(dev->dev, dma_dest, len, DMA_FROM_DEVICE);
                 return -ENOMEM;
+        }
 
         tx->ack = 1;
         tx->callback = NULL;
-        addr = dma_map_single(dev->dev, kdata, len, DMA_TO_DEVICE);
-        tx->tx_set_src(addr, tx, 0);
-        addr = dma_map_page(dev->dev, page, offset, len, DMA_FROM_DEVICE);
-        tx->tx_set_dest(addr, tx, 0);
         cookie = tx->tx_submit(tx);
 
         cpu = get_cpu();
@@ -563,20 +567,23 @@ dma_async_memcpy_pg_to_pg(struct dma_chan *chan, struct page *dest_pg,
 {
         struct dma_device *dev = chan->device;
         struct dma_async_tx_descriptor *tx;
-        dma_addr_t addr;
+        dma_addr_t dma_dest, dma_src;
         dma_cookie_t cookie;
         int cpu;
 
-        tx = dev->device_prep_dma_memcpy(chan, len, 0);
-        if (!tx)
+        dma_src = dma_map_page(dev->dev, src_pg, src_off, len, DMA_TO_DEVICE);
+        dma_dest = dma_map_page(dev->dev, dest_pg, dest_off, len,
+                                DMA_FROM_DEVICE);
+        tx = dev->device_prep_dma_memcpy(chan, dma_dest, dma_src, len, 0);
+
+        if (!tx) {
+                dma_unmap_page(dev->dev, dma_src, len, DMA_TO_DEVICE);
+                dma_unmap_page(dev->dev, dma_dest, len, DMA_FROM_DEVICE);
                 return -ENOMEM;
+        }
 
         tx->ack = 1;
         tx->callback = NULL;
-        addr = dma_map_page(dev->dev, src_pg, src_off, len, DMA_TO_DEVICE);
-        tx->tx_set_src(addr, tx, 0);
-        addr = dma_map_page(dev->dev, dest_pg, dest_off, len, DMA_FROM_DEVICE);
-        tx->tx_set_dest(addr, tx, 0);
         cookie = tx->tx_submit(tx);
 
         cpu = get_cpu();
diff --git a/drivers/dma/ioat_dma.c b/drivers/dma/ioat_dma.c
index 45e7b4666c7..5bcfc55a277 100644
--- a/drivers/dma/ioat_dma.c
+++ b/drivers/dma/ioat_dma.c
@@ -159,20 +159,6 @@ static int ioat_dma_enumerate_channels(struct ioatdma_device *device)
         return device->common.chancnt;
 }
 
-static void ioat_set_src(dma_addr_t addr,
-                         struct dma_async_tx_descriptor *tx,
-                         int index)
-{
-        tx_to_ioat_desc(tx)->src = addr;
-}
-
-static void ioat_set_dest(dma_addr_t addr,
-                          struct dma_async_tx_descriptor *tx,
-                          int index)
-{
-        tx_to_ioat_desc(tx)->dst = addr;
-}
-
 /**
  * ioat_dma_memcpy_issue_pending - push potentially unrecognized appended
  *                                 descriptors to hw
@@ -415,8 +401,6 @@ static struct ioat_desc_sw *ioat_dma_alloc_descriptor(
 
         memset(desc, 0, sizeof(*desc));
         dma_async_tx_descriptor_init(&desc_sw->async_tx, &ioat_chan->common);
-        desc_sw->async_tx.tx_set_src = ioat_set_src;
-        desc_sw->async_tx.tx_set_dest = ioat_set_dest;
         switch (ioat_chan->device->version) {
         case IOAT_VER_1_2:
                 desc_sw->async_tx.tx_submit = ioat1_tx_submit;
@@ -714,6 +698,8 @@ static struct ioat_desc_sw *ioat_dma_get_next_descriptor(
 
 static struct dma_async_tx_descriptor *ioat1_dma_prep_memcpy(
                                                 struct dma_chan *chan,
+                                                dma_addr_t dma_dest,
+                                                dma_addr_t dma_src,
                                                 size_t len,
                                                 int int_en)
 {
@@ -726,6 +712,8 @@ static struct dma_async_tx_descriptor *ioat1_dma_prep_memcpy(
 
         if (new) {
                 new->len = len;
+                new->dst = dma_dest;
+                new->src = dma_src;
                 return &new->async_tx;
         } else
                 return NULL;
@@ -733,6 +721,8 @@ static struct dma_async_tx_descriptor *ioat1_dma_prep_memcpy(
 
 static struct dma_async_tx_descriptor *ioat2_dma_prep_memcpy(
                                                 struct dma_chan *chan,
+                                                dma_addr_t dma_dest,
+                                                dma_addr_t dma_src,
                                                 size_t len,
                                                 int int_en)
 {
@@ -749,6 +739,8 @@ static struct dma_async_tx_descriptor *ioat2_dma_prep_memcpy(
 
         if (new) {
                 new->len = len;
+                new->dst = dma_dest;
+                new->src = dma_src;
                 return &new->async_tx;
         } else
                 return NULL;
@@ -1045,7 +1037,7 @@ static int ioat_dma_self_test(struct ioatdma_device *device)
         u8 *dest;
         struct dma_chan *dma_chan;
         struct dma_async_tx_descriptor *tx;
-        dma_addr_t addr;
+        dma_addr_t dma_dest, dma_src;
         dma_cookie_t cookie;
         int err = 0;
 
@@ -1073,7 +1065,12 @@ static int ioat_dma_self_test(struct ioatdma_device *device)
                 goto out;
         }
 
-        tx = device->common.device_prep_dma_memcpy(dma_chan, IOAT_TEST_SIZE, 0);
+        dma_src = dma_map_single(dma_chan->device->dev, src, IOAT_TEST_SIZE,
+                                 DMA_TO_DEVICE);
+        dma_dest = dma_map_single(dma_chan->device->dev, dest, IOAT_TEST_SIZE,
+                                  DMA_FROM_DEVICE);
+        tx = device->common.device_prep_dma_memcpy(dma_chan, dma_dest, dma_src,
+                                                   IOAT_TEST_SIZE, 0);
         if (!tx) {
                 dev_err(&device->pdev->dev,
                         "Self-test prep failed, disabling\n");
@@ -1082,12 +1079,6 @@ static int ioat_dma_self_test(struct ioatdma_device *device)
         }
 
         async_tx_ack(tx);
-        addr = dma_map_single(dma_chan->device->dev, src, IOAT_TEST_SIZE,
-                              DMA_TO_DEVICE);
-        tx->tx_set_src(addr, tx, 0);
-        addr = dma_map_single(dma_chan->device->dev, dest, IOAT_TEST_SIZE,
-                              DMA_FROM_DEVICE);
-        tx->tx_set_dest(addr, tx, 0);
         tx->callback = ioat_dma_test_callback;
         tx->callback_param = (void *)0x8086;
         cookie = tx->tx_submit(tx);
diff --git a/drivers/dma/iop-adma.c b/drivers/dma/iop-adma.c
index b011b5ae22a..eda841c6069 100644
--- a/drivers/dma/iop-adma.c
+++ b/drivers/dma/iop-adma.c
@@ -443,17 +443,6 @@ iop_adma_tx_submit(struct dma_async_tx_descriptor *tx)
         return cookie;
 }
 
-static void
-iop_adma_set_dest(dma_addr_t addr, struct dma_async_tx_descriptor *tx,
-        int index)
-{
-        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);
-
-        /* to do: support transfers lengths > IOP_ADMA_MAX_BYTE_COUNT */
-        iop_desc_set_dest_addr(sw_desc->group_head, iop_chan, addr);
-}
-
 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);
 
@@ -486,7 +475,6 @@ static int iop_adma_alloc_chan_resources(struct dma_chan *chan)
 
                 dma_async_tx_descriptor_init(&slot->async_tx, chan);
                 slot->async_tx.tx_submit = iop_adma_tx_submit;
-                slot->async_tx.tx_set_dest = iop_adma_set_dest;
                 INIT_LIST_HEAD(&slot->chain_node);
                 INIT_LIST_HEAD(&slot->slot_node);
                 INIT_LIST_HEAD(&slot->async_tx.tx_list);
@@ -547,18 +535,9 @@ iop_adma_prep_dma_interrupt(struct dma_chan *chan)
         return sw_desc ? &sw_desc->async_tx : NULL;
 }
 
-static void
-iop_adma_memcpy_set_src(dma_addr_t addr, struct dma_async_tx_descriptor *tx,
-        int index)
-{
-        struct iop_adma_desc_slot *sw_desc = tx_to_iop_adma_slot(tx);
-        struct iop_adma_desc_slot *grp_start = sw_desc->group_head;
-
-        iop_desc_set_memcpy_src_addr(grp_start, addr);
-}
-
 static struct dma_async_tx_descriptor *
-iop_adma_prep_dma_memcpy(struct dma_chan *chan, size_t len, int int_en)
+iop_adma_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dma_dest,
+                         dma_addr_t dma_src, size_t len, int int_en)
 {
         struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
         struct iop_adma_desc_slot *sw_desc, *grp_start;
@@ -578,9 +557,10 @@ iop_adma_prep_dma_memcpy(struct dma_chan *chan, size_t len, int int_en)
                 grp_start = sw_desc->group_head;
                 iop_desc_init_memcpy(grp_start, int_en);
                 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.tx_set_src = iop_adma_memcpy_set_src;
         }
         spin_unlock_bh(&iop_chan->lock);
 
@@ -588,8 +568,8 @@ iop_adma_prep_dma_memcpy(struct dma_chan *chan, size_t len, int int_en)
 }
 
 static struct dma_async_tx_descriptor *
-iop_adma_prep_dma_memset(struct dma_chan *chan, int value, size_t len,
-        int int_en)
+iop_adma_prep_dma_memset(struct dma_chan *chan, dma_addr_t dma_dest,
+                         int value, size_t len, int int_en)
 {
         struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
         struct iop_adma_desc_slot *sw_desc, *grp_start;
@@ -610,6 +590,7 @@ iop_adma_prep_dma_memset(struct dma_chan *chan, int value, size_t len,
                 iop_desc_init_memset(grp_start, int_en);
                 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;
         }
@@ -618,19 +599,10 @@ iop_adma_prep_dma_memset(struct dma_chan *chan, int value, size_t len,
         return sw_desc ? &sw_desc->async_tx : NULL;
 }
 
-static void
-iop_adma_xor_set_src(dma_addr_t addr, struct dma_async_tx_descriptor *tx,
-        int index)
-{
-        struct iop_adma_desc_slot *sw_desc = tx_to_iop_adma_slot(tx);
-        struct iop_adma_desc_slot *grp_start = sw_desc->group_head;
-
-        iop_desc_set_xor_src_addr(grp_start, index, addr);
-}
-
 static struct dma_async_tx_descriptor *
-iop_adma_prep_dma_xor(struct dma_chan *chan, unsigned int src_cnt, size_t len,
-        int int_en)
+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,
+                      int int_en)
 {
         struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
         struct iop_adma_desc_slot *sw_desc, *grp_start;
@@ -651,29 +623,22 @@ iop_adma_prep_dma_xor(struct dma_chan *chan, unsigned int src_cnt, size_t len,
                 grp_start = sw_desc->group_head;
                 iop_desc_init_xor(grp_start, src_cnt, int_en);
                 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.tx_set_src = iop_adma_xor_set_src;
+                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 void
-iop_adma_xor_zero_sum_set_src(dma_addr_t addr,
-                                struct dma_async_tx_descriptor *tx,
-                                int index)
-{
-        struct iop_adma_desc_slot *sw_desc = tx_to_iop_adma_slot(tx);
-        struct iop_adma_desc_slot *grp_start = sw_desc->group_head;
-
-        iop_desc_set_zero_sum_src_addr(grp_start, index, addr);
-}
-
 static struct dma_async_tx_descriptor *
-iop_adma_prep_dma_zero_sum(struct dma_chan *chan, unsigned int src_cnt,
-        size_t len, u32 *result, int int_en)
+iop_adma_prep_dma_zero_sum(struct dma_chan *chan, dma_addr_t *dma_src,
+                           unsigned int src_cnt, size_t len, u32 *result,
+                           int int_en)
 {
         struct iop_adma_chan *iop_chan = to_iop_adma_chan(chan);
         struct iop_adma_desc_slot *sw_desc, *grp_start;
@@ -697,7 +662,9 @@ iop_adma_prep_dma_zero_sum(struct dma_chan *chan, unsigned int src_cnt,
                         __FUNCTION__, grp_start->xor_check_result);
                 sw_desc->unmap_src_cnt = src_cnt;
                 sw_desc->unmap_len = len;
-                sw_desc->async_tx.tx_set_src = iop_adma_xor_zero_sum_set_src;
+                while (src_cnt--)
+                        iop_desc_set_zero_sum_src_addr(grp_start, src_cnt,
+                                                       dma_src[src_cnt]);
         }
         spin_unlock_bh(&iop_chan->lock);
 
@@ -882,13 +849,12 @@ static int __devinit iop_adma_memcpy_self_test(struct iop_adma_device *device)
                 goto out;
         }
 
-        tx = iop_adma_prep_dma_memcpy(dma_chan, IOP_ADMA_TEST_SIZE, 1);
         dest_dma = dma_map_single(dma_chan->device->dev, dest,
                                 IOP_ADMA_TEST_SIZE, DMA_FROM_DEVICE);
-        iop_adma_set_dest(dest_dma, tx, 0);
         src_dma = dma_map_single(dma_chan->device->dev, src,
                                 IOP_ADMA_TEST_SIZE, DMA_TO_DEVICE);
-        iop_adma_memcpy_set_src(src_dma, tx, 0);
+        tx = iop_adma_prep_dma_memcpy(dma_chan, dest_dma, src_dma,
+                                      IOP_ADMA_TEST_SIZE, 1);
 
         cookie = iop_adma_tx_submit(tx);
         iop_adma_issue_pending(dma_chan);
@@ -929,6 +895,7 @@ iop_adma_xor_zero_sum_self_test(struct iop_adma_device *device)
         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;
@@ -981,17 +948,13 @@ iop_adma_xor_zero_sum_self_test(struct iop_adma_device *device)
         }
 
         /* test xor */
-        tx = iop_adma_prep_dma_xor(dma_chan, IOP_ADMA_NUM_SRC_TEST,
-                                PAGE_SIZE, 1);
         dest_dma = dma_map_page(dma_chan->device->dev, dest, 0,
                                 PAGE_SIZE, DMA_FROM_DEVICE);
-        iop_adma_set_dest(dest_dma, tx, 0);
-
-        for (i = 0; i < IOP_ADMA_NUM_SRC_TEST; i++) {
-                dma_addr = dma_map_page(dma_chan->device->dev, xor_srcs[i], 0,
-                        PAGE_SIZE, DMA_TO_DEVICE);
-                iop_adma_xor_set_src(dma_addr, tx, i);
-        }
+        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, 1);
 
         cookie = iop_adma_tx_submit(tx);
         iop_adma_issue_pending(dma_chan);
@@ -1032,13 +995,13 @@ iop_adma_xor_zero_sum_self_test(struct iop_adma_device *device)
 
         zero_sum_result = 1;
 
-        tx = iop_adma_prep_dma_zero_sum(dma_chan, IOP_ADMA_NUM_SRC_TEST + 1,
-                PAGE_SIZE, &zero_sum_result, 1);
-        for (i = 0; i < IOP_ADMA_NUM_SRC_TEST + 1; i++) {
-                dma_addr = dma_map_page(dma_chan->device->dev, zero_sum_srcs[i],
-                        0, PAGE_SIZE, DMA_TO_DEVICE);
-                iop_adma_xor_zero_sum_set_src(dma_addr, tx, i);
-        }
+        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, 1);
 
         cookie = iop_adma_tx_submit(tx);
         iop_adma_issue_pending(dma_chan);
@@ -1060,10 +1023,9 @@ iop_adma_xor_zero_sum_self_test(struct iop_adma_device *device)
         }
 
         /* test memset */
-        tx = iop_adma_prep_dma_memset(dma_chan, 0, PAGE_SIZE, 1);
         dma_addr = dma_map_page(dma_chan->device->dev, dest, 0,
                         PAGE_SIZE, DMA_FROM_DEVICE);
-        iop_adma_set_dest(dma_addr, tx, 0);
+        tx = iop_adma_prep_dma_memset(dma_chan, dma_addr, 0, PAGE_SIZE, 1);
 
         cookie = iop_adma_tx_submit(tx);
         iop_adma_issue_pending(dma_chan);
@@ -1089,13 +1051,13 @@ iop_adma_xor_zero_sum_self_test(struct iop_adma_device *device)
 
         /* test for non-zero parity sum */
         zero_sum_result = 0;
-        tx = iop_adma_prep_dma_zero_sum(dma_chan, IOP_ADMA_NUM_SRC_TEST + 1,
-                PAGE_SIZE, &zero_sum_result, 1);
-        for (i = 0; i < IOP_ADMA_NUM_SRC_TEST + 1; i++) {
-                dma_addr = dma_map_page(dma_chan->device->dev, zero_sum_srcs[i],
-                        0, PAGE_SIZE, DMA_TO_DEVICE);
-                iop_adma_xor_zero_sum_set_src(dma_addr, tx, i);
-        }
+        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, 1);
 
         cookie = iop_adma_tx_submit(tx);
         iop_adma_issue_pending(dma_chan);