1 files changed, 13 insertions, 10 deletions

diff --git a/drivers/spi/spi_s3c24xx.c b/drivers/spi/spi_s3c24xx.c
index e0d44af4745a..3f3119d760db 100644
--- a/drivers/spi/spi_s3c24xx.c
+++ b/drivers/spi/spi_s3c24xx.c
@@ -111,29 +111,32 @@ static int s3c24xx_spi_setupxfer(struct spi_device *spi,
         unsigned int bpw;
         unsigned int hz;
         unsigned int div;
+        unsigned long clk;
 
         bpw = t ? t->bits_per_word : spi->bits_per_word;
         hz  = t ? t->speed_hz : spi->max_speed_hz;
 
+        if (!bpw)
+                bpw = 8;
+
+        if (!hz)
+                hz = spi->max_speed_hz;
+
         if (bpw != 8) {
                 dev_err(&spi->dev, "invalid bits-per-word (%d)\n", bpw);
                 return -EINVAL;
         }
 
-        div = clk_get_rate(hw->clk) / hz;
-
-        /* is clk = pclk / (2 * (pre+1)), or is it
-         *    clk = (pclk * 2) / ( pre + 1) */
-
-        div /= 2;
-
-        if (div > 0)
-                div -= 1;
+        clk = clk_get_rate(hw->clk);
+        div = DIV_ROUND_UP(clk, hz * 2) - 1;
 
         if (div > 255)
                 div = 255;
 
-        dev_dbg(&spi->dev, "setting pre-scaler to %d (hz %d)\n", div, hz);
+        dev_dbg(&spi->dev, "setting pre-scaler to %d (wanted %d, got %ld)\n",
+                div, hz, clk / (2 * (div + 1)));
+
+
         writeb(div, hw->regs + S3C2410_SPPRE);
 
         spin_lock(&hw->bitbang.lock);