spi: spi-qcom-qspi: Call dma_wmb() after setting up descriptors

After setting up dma descriptors and before initiaiting dma transfer, call
dma_wmb() to ensure all writes go through.
This doesn't fix any reported problem but is added for safety.

Signed-off-by: Vijaya Krishna Nivarthi <[email protected]>
Fixes: b5762d9 ("spi: spi-qcom-qspi: Add DMA mode support")
Reviewed-by: Douglas Anderson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: Vijaya Krishna Nivarthi

drivers/spi/spi-qcom-qspi.c

@@ -443,8 +443,10 @@ static int qcom_qspi_transfer_one(struct spi_master *master,
 
 		ret = qcom_qspi_setup_dma_desc(ctrl, xfer);
 		if (ret != -EAGAIN) {
-			if (!ret)
+			if (!ret) {
+				dma_wmb();
 				qcom_qspi_dma_xfer(ctrl);
+			}
 			goto exit;
 		}
 		dev_warn_once(ctrl->dev, "DMA failure, falling back to PIO\n");