ioat3: enable dca for completion writes

Tag completion writes for direct cache access to reduce the latency of
checking for descriptor completions.

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

drivers/dma/ioat/dma_v3.c

@@ -167,7 +167,8 @@ static void ioat3_cleanup_tasklet(unsigned long data)
 	struct ioat2_dma_chan *ioat = (void *) data;
 
 	ioat3_cleanup(ioat);
-	writew(IOAT_CHANCTRL_RUN, ioat->base.reg_base + IOAT_CHANCTRL_OFFSET);
+	writew(IOAT_CHANCTRL_RUN | IOAT3_CHANCTRL_COMPL_DCA_EN,
+	       ioat->base.reg_base + IOAT_CHANCTRL_OFFSET);
 }
 
 static void ioat3_restart_channel(struct ioat2_dma_chan *ioat)

drivers/dma/ioat/registers.h

@@ -84,6 +84,7 @@
 /* DMA Channel Registers */
 #define IOAT_CHANCTRL_OFFSET			0x00	/* 16-bit Channel Control Register */
 #define IOAT_CHANCTRL_CHANNEL_PRIORITY_MASK	0xF000
+#define IOAT3_CHANCTRL_COMPL_DCA_EN		0x0200
 #define IOAT_CHANCTRL_CHANNEL_IN_USE		0x0100
 #define IOAT_CHANCTRL_DESCRIPTOR_ADDR_SNOOP_CONTROL	0x0020
 #define IOAT_CHANCTRL_ERR_INT_EN		0x0010