ioat3: interrupt descriptor support

The async_tx api uses the DMA_INTERRUPT operation type to terminate a
chain of issued operations with a callback routine.
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/dma/ioat/dma_v3.c

@@ -120,7 +120,8 @@ static void ioat3_dma_unmap(struct ioat2_dma_chan *ioat,
 
 	switch (desc->hw->ctl_f.op) {
 	case IOAT_OP_COPY:
-		ioat_dma_unmap(chan, flags, len, desc->hw);
+		if (!desc->hw->ctl_f.null) /* skip 'interrupt' ops */
+			ioat_dma_unmap(chan, flags, len, desc->hw);
 		break;
 	case IOAT_OP_FILL: {
 		struct ioat_fill_descriptor *hw = desc->fill;
@@ -804,6 +805,38 @@ ioat3_prep_pqxor_val(struct dma_chan *chan, dma_addr_t *src,
 				    len, flags);
 }
 
+static struct dma_async_tx_descriptor *
+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);
+	else
+		return NULL;
+
+	hw = desc->hw;
+	hw->ctl = 0;
+	hw->ctl_f.null = 1;
+	hw->ctl_f.int_en = 1;
+	hw->ctl_f.fence = !!(flags & DMA_PREP_FENCE);
+	hw->ctl_f.compl_write = 1;
+	hw->size = NULL_DESC_BUFFER_SIZE;
+	hw->src_addr = 0;
+	hw->dst_addr = 0;
+
+	desc->txd.flags = flags;
+	desc->len = 1;
+
+	dump_desc_dbg(ioat, desc);
+
+	/* we leave the channel locked to ensure in order submission */
+	return &desc->txd;
+}
+
 static void __devinit ioat3_dma_test_callback(void *dma_async_param)
 {
 	struct completion *cmp = dma_async_param;
@@ -1098,6 +1131,10 @@ int __devinit ioat3_dma_probe(struct ioatdma_device *device, int dca)
 	dma->device_alloc_chan_resources = ioat2_alloc_chan_resources;
 	dma->device_free_chan_resources = ioat2_free_chan_resources;
 	dma->device_is_tx_complete = ioat3_is_complete;
+
+	dma_cap_set(DMA_INTERRUPT, dma->cap_mask);
+	dma->device_prep_dma_interrupt = ioat3_prep_interrupt_lock;
+
 	cap = readl(device->reg_base + IOAT_DMA_CAP_OFFSET);
 	if (cap & IOAT_CAP_FILL_BLOCK) {
 		dma_cap_set(DMA_MEMSET, dma->cap_mask);