[PATCH v3] spi: dw: support 4-16 bits per word

[Simon Goldschmidt]

The spi-dw driver currently only supports 8 or 16 bits per word.

Since the hardware supports 4-16 bits per word, adapt the driver
to also support this.

Tested on socfpga cyclone5 with a 9-bit SPI display.

Signed-off-by: Simon Goldschmidt <simon.k.r.goldschm...@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevche...@gmail.com>
---
Changes in v3
- remove the check for valid 'bits_per_word' from dw_spi_transfer_one()
- add reviewed-by tag

Changes in v2:
- use DIV_ROUND_UP to calculate number of bytes per word instead of
  if/else range checks

 drivers/spi/spi-dw.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
index f693bfe95ab9..58a7caf31d59 100644
--- a/drivers/spi/spi-dw.c
+++ b/drivers/spi/spi-dw.c
@@ -307,15 +307,10 @@ static int dw_spi_transfer_one(struct spi_controller 
*master,
                dws->current_freq = transfer->speed_hz;
                spi_set_clk(dws, chip->clk_div);
        }
-       if (transfer->bits_per_word == 8) {
-               dws->n_bytes = 1;
-               dws->dma_width = 1;
-       } else if (transfer->bits_per_word == 16) {
-               dws->n_bytes = 2;
-               dws->dma_width = 2;
-       } else {
-               return -EINVAL;
-       }
+
+       dws->n_bytes = DIV_ROUND_UP(transfer->bits_per_word, BITS_PER_BYTE);
+       dws->dma_width = DIV_ROUND_UP(transfer->bits_per_word, BITS_PER_BYTE);
+
        /* Default SPI mode is SCPOL = 0, SCPH = 0 */
        cr0 = (transfer->bits_per_word - 1)
                | (chip->type << SPI_FRF_OFFSET)
@@ -493,7 +491,7 @@ int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
        }
 
        master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP;
-       master->bits_per_word_mask = SPI_BPW_MASK(8) | SPI_BPW_MASK(16);
+       master->bits_per_word_mask =  SPI_BPW_RANGE_MASK(4, 16);
        master->bus_num = dws->bus_num;
        master->num_chipselect = dws->num_cs;
        master->setup = dw_spi_setup;
-- 
2.17.1