[PATCH v2 2/2] ntb_hw_switchtec: Check for alignment of the buffer in mw_set_trans()

From: Logan Gunthorpe
Date: Mon Dec 18 2017 - 13:25:41 EST

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 <logang@xxxxxxxxxxxx>
Cc: Jon Mason <jdmason@xxxxxxxx>

v2: Use IS_ALIGNED macro as suggested by Allen

drivers/ntb/hw/mscc/ntb_hw_switchtec.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/drivers/ntb/hw/mscc/ntb_hw_switchtec.c b/drivers/ntb/hw/mscc/ntb_hw_switchtec.c
index bcd5b6fb3800..6c6f991999b5 100644
--- a/drivers/ntb/hw/mscc/ntb_hw_switchtec.c
+++ b/drivers/ntb/hw/mscc/ntb_hw_switchtec.c
@@ -320,6 +320,19 @@ static int switchtec_ntb_mw_set_trans(struct ntb_dev *ntb, int pidx, int widx,
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
+ */
+ 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,
if (rc)