ntb_hw_switchtec: Check for alignment of the buffer in mw_set_trans()

With Switchtec hardware, the buffer used for a memory window must be
aligned to its size (the hardware only replaces the lower bits). In
certain circumstances dma_alloc_coherent() will not provide a buffer
that adheres to this requirement like when using the CMA and
CONFIG_CMA_ALIGNMENT is set lower than the buffer size.

When we get an unaligned buffer mw_set_trans() should return an error.
We also log an error so we know the cause of the problem.

Signed-off-by: Logan Gunthorpe <[e-mail]>
Signed-off-by: Jon Mason <[e-mail]>

drivers/ntb/hw/mscc/ntb_hw_switchtec.c

···
 	if (xlate_pos < 12)
 		return -EINVAL;
 
+	if (!IS_ALIGNED(addr, BIT_ULL(xlate_pos))) {
+		/*
+		 * In certain circumstances we can get a buffer that is
+		 * not aligned to its size. (Most of the time
+		 * dma_alloc_coherent ensures this). This can happen when
+		 * using large buffers allocated by the CMA
+		 * (see CMA_CONFIG_ALIGNMENT)
+		 */
+		dev_err(&sndev->stdev->dev,
+			"ERROR: Memory window address is not aligned to it's size!\n");
+		return -EINVAL;
+	}
+
 	rc = switchtec_ntb_part_op(sndev, ctl, NTB_CTRL_PART_OP_LOCK,
 				   NTB_CTRL_PART_STATUS_LOCKED);
 	if (rc)