spi: fsl-espi: reject MSB-first transfers with word sizes other than 8 or 16

According to the ESPI spec MSB-first transfers are supported for
word size 8 and 16 only.

Check for this and reject MSB-first transfers with other word sizes.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-fsl-espi.c

@@ -153,6 +153,7 @@ static int fsl_espi_check_message(struct spi_message *m)
 
 	first = list_first_entry(&m->transfers, struct spi_transfer,
 				 transfer_list);
+
 	list_for_each_entry(t, &m->transfers, transfer_list) {
 		if (first->bits_per_word != t->bits_per_word ||
 		    first->speed_hz != t->speed_hz) {
@@ -161,6 +162,15 @@ static int fsl_espi_check_message(struct spi_message *m)
 		}
 	}
 
+	/* ESPI supports MSB-first transfers for word size 8 / 16 only */
+	if (!(m->spi->mode & SPI_LSB_FIRST) && first->bits_per_word != 8 &&
+	    first->bits_per_word != 16) {
+		dev_err(mspi->dev,
+			"MSB-first transfer not supported for wordsize %u\n",
+			first->bits_per_word);
+		return -EINVAL;
+	}
+
 	return 0;
 }