spi/spi-fsl-spi: Add support for setting a maximum number of bits per word

Acked-by: Anton Vorontsov <anton@enomsg.org>
Signed-off-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/spi-fsl-lib.h

@@ -71,6 +71,7 @@ struct mpc8xxx_spi {
 
 #ifdef CONFIG_SPI_FSL_SPI
 	int type;
+	u8 max_bits_per_word;
 
 	void (*set_shifts)(u32 *rx_shift, u32 *tx_shift,
 			   int bits_per_word, int msb_first);

drivers/spi/spi-fsl-spi.c

@@ -213,7 +213,8 @@ static int fsl_spi_setup_transfer(struct spi_device *spi,
 
 	/* Make sure its a bit width we support [4..16, 32] */
 	if ((bits_per_word < 4)
-	    || ((bits_per_word > 16) && (bits_per_word != 32)))
+	    || ((bits_per_word > 16) && (bits_per_word != 32))
+	    || (bits_per_word > mpc8xxx_spi->max_bits_per_word))
 		return -EINVAL;
 
 	if (!hz)
@@ -520,6 +521,7 @@ static struct spi_master * fsl_spi_probe(struct device *dev,
 	mpc8xxx_spi = spi_master_get_devdata(master);
 	mpc8xxx_spi->spi_do_one_msg = fsl_spi_do_one_msg;
 	mpc8xxx_spi->spi_remove = fsl_spi_remove;
+	mpc8xxx_spi->max_bits_per_word = 32;
 	mpc8xxx_spi->type = fsl_spi_get_type(dev);
 
 	ret = fsl_spi_cpm_init(mpc8xxx_spi);
@@ -557,6 +559,10 @@ static struct spi_master * fsl_spi_probe(struct device *dev,
 
 	/* Enable SPI interface */
 	regval = pdata->initial_spmode | SPMODE_INIT_VAL | SPMODE_ENABLE;
+	if (mpc8xxx_spi->max_bits_per_word < 8) {
+		regval &= ~SPMODE_LEN(0xF);
+		regval |= SPMODE_LEN(mpc8xxx_spi->max_bits_per_word - 1);
+	}
 	if (mpc8xxx_spi->flags & SPI_QE_CPU_MODE)
 		regval |= SPMODE_OP;