dmaengine: ioatdma: disable relaxed ordering for ioatdma

ioatdma by default is in snoop mode. Relaxed ordering according to spec
does not do anything in snoop mode. However, it causes hang or significant
performance degrade when tested with NTB. Disabling in the driver due to
some BIOS do not configure it correctly.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/ioat/init.c

@@ -1073,6 +1073,7 @@ static int ioat3_dma_probe(struct ioatdma_device *ioat_dma, int dca)
 	struct ioatdma_chan *ioat_chan;
 	bool is_raid_device = false;
 	int err;
+	u16 val16;
 
 	dma = &ioat_dma->dma_dev;
 	dma->device_prep_dma_memcpy = ioat_dma_prep_memcpy_lock;
@@ -1172,6 +1173,17 @@ static int ioat3_dma_probe(struct ioatdma_device *ioat_dma, int dca)
 	if (dca)
 		ioat_dma->dca = ioat_dca_init(pdev, ioat_dma->reg_base);
 
+	/* disable relaxed ordering */
+	err = pcie_capability_read_word(pdev, IOAT_DEVCTRL_OFFSET, &val16);
+	if (err)
+		return err;
+
+	/* clear relaxed ordering enable */
+	val16 &= ~IOAT_DEVCTRL_ROE;
+	err = pcie_capability_write_word(pdev, IOAT_DEVCTRL_OFFSET, val16);
+	if (err)
+		return err;
+
 	return 0;
 }
 

drivers/dma/ioat/registers.h

@@ -26,6 +26,13 @@
 #define IOAT_PCI_CHANERR_INT_OFFSET		0x180
 #define IOAT_PCI_CHANERRMASK_INT_OFFSET		0x184
 
+/* PCIe config registers */
+
+/* EXPCAPID + N */
+#define IOAT_DEVCTRL_OFFSET			0x8
+/* relaxed ordering enable */
+#define IOAT_DEVCTRL_ROE			0x10
+
 /* MMIO Device Registers */
 #define IOAT_CHANCNT_OFFSET			0x00	/*  8-bit */