spi: npcm-pspi: improve spi transfer performance

Improving spi 8 bit per word mode transfer performance
by using 16 bit per word transfer and receive when the data
length is even and larger than one.

Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
Link: https://lore.kernel.org/r/20200115162301.235926-3-tmaimon77@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-npcm-pspi.c

@@ -178,6 +178,13 @@ static void npcm_pspi_setup_transfer(struct spi_device *spi,
 		priv->mode = spi->mode;
 	}
 
+	/*
+	 * If transfer is even length, and 8 bits per word transfer,
+	 * then implement 16 bits-per-word transfer.
+	 */
+	if (priv->bits_per_word == 8 && !(t->len & 0x1))
+		t->bits_per_word = 16;
+
 	if (!priv->is_save_param || priv->bits_per_word != t->bits_per_word) {
 		npcm_pspi_set_transfer_size(priv, t->bits_per_word);
 		priv->bits_per_word = t->bits_per_word;