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>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/spi/spi-fsl-espi.c b/drivers/spi/spi-fsl-espi.c
index 1f97cce615d3..65bb70d3bfc4 100644
--- a/drivers/spi/spi-fsl-espi.c
+++ b/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;
 }