spi/atmel: let transfers through if not changing bits_per_word

bits_per_word option in spi_transfer are allowed if it does not change
the csr register.

This is necessary for the driver in
drivers/staging/iio/adis16260_core.c, as it uses this option.

Signed-off-by: Matthias Brugger <mensch0815@gmail.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 13 insertions, 1 deletions

diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c
index c4e04428992d..5c03a5bb168a 100644
--- a/drivers/spi/atmel_spi.c
+++ b/drivers/spi/atmel_spi.c
@@ -654,6 +654,8 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
         struct spi_transfer     *xfer;
         unsigned long           flags;
         struct device           *controller = spi->master->dev.parent;
+        u8                      bits;
+        struct atmel_spi_device *asd;
 
         as = spi_master_get_devdata(spi->master);
 
@@ -672,8 +674,18 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
                         return -EINVAL;
                 }
 
+                if (xfer->bits_per_word) {
+                        asd = spi->controller_state;
+                        bits = (asd->csr >> 4) & 0xf;
+                        if (bits != xfer->bits_per_word - 8) {
+                                dev_dbg(&spi->dev, "you can't yet change "
+                                         "bit_per_word in transfers\n");
+                                return -ENOPROTOOPT;
+                        }
+                }
+
                 /* FIXME implement these protocol options!! */
-                if (xfer->bits_per_word || xfer->speed_hz) {
+                if (xfer->speed_hz) {
                         dev_dbg(&spi->dev, "no protocol options yet\n");
                         return -ENOPROTOOPT;
                 }