SPI100k: Fix 8-bit and RX-only transfers

This change fixes 8-bit transfers and RX-only transfers.  The
SPI100k framework requires minimum 16-bit words to be written, so 8-bit
transfers must be shited by 8 bits and sent out as a 16-bit word.

Additionally, receive-only transfers were failing due to the
perceived need to fill the TX buffer with something.  This is in
fact not needed.

Signed-off-by: Cory Maccarrone <darkstar6262@gmail.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 12 insertions, 11 deletions

diff --git a/drivers/spi/omap_spi_100k.c b/drivers/spi/omap_spi_100k.c
index 24668b30a52d..9bd1c92ad96e 100644
--- a/drivers/spi/omap_spi_100k.c
+++ b/drivers/spi/omap_spi_100k.c
@@ -141,7 +141,12 @@ static void spi100k_write_data(struct spi_master *master, int len, int data)
 {
         struct omap1_spi100k *spi100k = spi_master_get_devdata(master);
 
-        /* write 16-bit word */
+        /* write 16-bit word, shifting 8-bit data if necessary */
+        if (len <= 8) {
+                data <<= 8;
+                len = 16;
+        }
+
         spi100k_enable_clock(master);
         writew( data , spi100k->base + SPI_TX_MSB);
 
@@ -162,6 +167,10 @@ static int spi100k_read_data(struct spi_master *master, int len)
         int dataH,dataL;
         struct omap1_spi100k *spi100k = spi_master_get_devdata(master);
 
+        /* Always do at least 16 bits */
+        if (len <= 8)
+                len = 16;
+
         spi100k_enable_clock(master);
         writew(SPI_CTRL_SEN(0) |
                SPI_CTRL_WORD_SIZE(len) |
@@ -214,10 +223,6 @@ omap1_spi100k_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
         c = count;
         word_len = cs->word_len;
 
-        /* RX_ONLY mode needs dummy data in TX reg */
-        if (xfer->tx_buf == NULL)
-                spi100k_write_data(spi->master,word_len, 0);
-
         if (word_len <= 8) {
                 u8              *rx;
                 const u8        *tx;
@@ -227,9 +232,9 @@ omap1_spi100k_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
                 do {
                         c-=1;
                         if (xfer->tx_buf != NULL)
-                                spi100k_write_data(spi->master,word_len, *tx);
+                                spi100k_write_data(spi->master, word_len, *tx++);
                         if (xfer->rx_buf != NULL)
-                                *rx = spi100k_read_data(spi->master,word_len);
+                                *rx++ = spi100k_read_data(spi->master, word_len);
                 } while(c);
         } else if (word_len <= 16) {
                 u16             *rx;
@@ -380,10 +385,6 @@ static void omap1_spi100k_work(struct work_struct *work)
                         if (t->len) {
                                 unsigned count;
 
-                                /* RX_ONLY mode needs dummy data in TX reg */
-                                if (t->tx_buf == NULL)
-                                        spi100k_write_data(spi->master, 8, 0);
-
                                 count = omap1_spi100k_txrx_pio(spi, t);
                                 m->actual_length += count;