diff --git a/drivers/spi/omap_uwire.c b/drivers/spi/omap_uwire.c
index 95183e1..d275c61 100644
--- a/drivers/spi/omap_uwire.c
+++ b/drivers/spi/omap_uwire.c
@@ -445,10 +445,19 @@
 	return status;
 }
 
+/* the spi->mode bits understood by this driver: */
+#define MODEBITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH)
+
 static int uwire_setup(struct spi_device *spi)
 {
 	struct uwire_state *ust = spi->controller_state;
 
+	if (spi->mode & ~MODEBITS) {
+		dev_dbg(&spi->dev, "setup: unsupported mode bits %x\n",
+			spi->mode & ~MODEBITS);
+		return -EINVAL;
+	}
+
 	if (ust == NULL) {
 		ust = kzalloc(sizeof(*ust), GFP_KERNEL);
 		if (ust == NULL)