dma: mv_xor: Add support for DMA_INTERRUPT

The driver is capable of supporting DMA_INTERRUPT by issuing a dummy 128-byte
transfer. This helps removing a poll in the async_tx stack, replacing it with
a completion interrupt.

Signed-off-by: Lior Amsalem <alior@marvell.com>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

2 files changed, 40 insertions, 5 deletions

diff --git a/drivers/dma/mv_xor.c b/drivers/dma/mv_xor.c
index 744a0077e5aa..769d35c3a82b 100644
--- a/drivers/dma/mv_xor.c
+++ b/drivers/dma/mv_xor.c
@@ -538,6 +538,24 @@ mv_xor_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
         return mv_xor_prep_dma_xor(chan, dest, &src, 1, len, flags);
 }
 
+static struct dma_async_tx_descriptor *
+mv_xor_prep_dma_interrupt(struct dma_chan *chan, unsigned long flags)
+{
+        struct mv_xor_chan *mv_chan = to_mv_xor_chan(chan);
+        dma_addr_t src, dest;
+        size_t len;
+
+        src = mv_chan->dummy_src_addr;
+        dest = mv_chan->dummy_dst_addr;
+        len = MV_XOR_MIN_BYTE_COUNT;
+
+        /*
+         * We implement the DMA_INTERRUPT operation as a minimum sized
+         * XOR operation with a single dummy source address.
+         */
+        return mv_xor_prep_dma_xor(chan, dest, &src, 1, len, flags);
+}
+
 static void mv_xor_free_chan_resources(struct dma_chan *chan)
 {
         struct mv_xor_chan *mv_chan = to_mv_xor_chan(chan);
@@ -881,6 +899,10 @@ static int mv_xor_channel_remove(struct mv_xor_chan *mv_chan)
 
         dma_free_coherent(dev, MV_XOR_POOL_SIZE,
                           mv_chan->dma_desc_pool_virt, mv_chan->dma_desc_pool);
+        dma_unmap_single(dev, mv_chan->dummy_src_addr,
+                         MV_XOR_MIN_BYTE_COUNT, DMA_FROM_DEVICE);
+        dma_unmap_single(dev, mv_chan->dummy_dst_addr,
+                         MV_XOR_MIN_BYTE_COUNT, DMA_TO_DEVICE);
 
         list_for_each_entry_safe(chan, _chan, &mv_chan->dmadev.channels,
                                  device_node) {
@@ -910,6 +932,16 @@ mv_xor_channel_add(struct mv_xor_device *xordev,
 
         dma_dev = &mv_chan->dmadev;
 
+        /*
+         * These source and destination dummy buffers are used to implement
+         * a DMA_INTERRUPT operation as a minimum-sized XOR operation.
+         * Hence, we only need to map the buffers at initialization-time.
+         */
+        mv_chan->dummy_src_addr = dma_map_single(dma_dev->dev,
+                mv_chan->dummy_src, MV_XOR_MIN_BYTE_COUNT, DMA_FROM_DEVICE);
+        mv_chan->dummy_dst_addr = dma_map_single(dma_dev->dev,
+                mv_chan->dummy_dst, MV_XOR_MIN_BYTE_COUNT, DMA_TO_DEVICE);
+
         /* allocate coherent memory for hardware descriptors
          * note: writecombine gives slightly better performance, but
          * requires that we explicitly flush the writes
@@ -934,6 +966,8 @@ mv_xor_channel_add(struct mv_xor_device *xordev,
         dma_dev->dev = &pdev->dev;
 
         /* set prep routines based on capability */
+        if (dma_has_cap(DMA_INTERRUPT, dma_dev->cap_mask))
+                dma_dev->device_prep_dma_interrupt = mv_xor_prep_dma_interrupt;
         if (dma_has_cap(DMA_MEMCPY, dma_dev->cap_mask))
                 dma_dev->device_prep_dma_memcpy = mv_xor_prep_dma_memcpy;
         if (dma_has_cap(DMA_XOR, dma_dev->cap_mask)) {
diff --git a/drivers/dma/mv_xor.h b/drivers/dma/mv_xor.h
index de400365bc49..78edc7e44569 100644
--- a/drivers/dma/mv_xor.h
+++ b/drivers/dma/mv_xor.h
@@ -28,6 +28,9 @@
 #define MV_XOR_THRESHOLD                1
 #define MV_XOR_MAX_CHANNELS             2
 
+#define MV_XOR_MIN_BYTE_COUNT           SZ_128
+#define MV_XOR_MAX_BYTE_COUNT           (SZ_16M - 1)
+
 /* Values for the XOR_CONFIG register */
 #define XOR_OPERATION_MODE_XOR          0
 #define XOR_OPERATION_MODE_MEMCPY       2
@@ -116,6 +119,9 @@ struct mv_xor_chan {
         struct list_head        all_slots;
         int                     slots_allocated;
         struct tasklet_struct   irq_tasklet;
+        char                    dummy_src[MV_XOR_MIN_BYTE_COUNT];
+        char                    dummy_dst[MV_XOR_MIN_BYTE_COUNT];
+        dma_addr_t              dummy_src_addr, dummy_dst_addr;
 };
 
 /**
@@ -184,9 +190,4 @@ struct mv_xor_desc {
 #define mv_hw_desc_slot_idx(hw_desc, idx)       \
         ((void *)(((unsigned long)hw_desc) + ((idx) << 5)))
 
-#define MV_XOR_MIN_BYTE_COUNT   (128)
-#define XOR_MAX_BYTE_COUNT      ((16 * 1024 * 1024) - 1)
-#define MV_XOR_MAX_BYTE_COUNT   XOR_MAX_BYTE_COUNT
-
-
 #endif