spi: davinci: Set prescale value based on register value

[firefly-linux-kernel-4.4.55.git] / drivers / spi / spi-davinci.c

diff --git a/drivers/spi/spi-davinci.c b/drivers/spi/spi-davinci.c
index 987afebea09379507f2c8505e7f4c14acbde079c..b4605c4158f42d5860e069c81f15e8f4c0a0506d 100644 (file)
--- a/drivers/spi/spi-davinci.c
+++ b/drivers/spi/spi-davinci.c
@@ -255,7 +255,7 @@ static void davinci_spi_chipselect(struct spi_device *spi, int value)
  * This function calculates the prescale value that generates a clock rate
  * less than or equal to the specified maximum.
  *
- * Returns: calculated prescale - 1 for easy programming into SPI registers
+ * Returns: calculated prescale value for easy programming into SPI registers
  * or negative error number if valid prescalar cannot be updated.
  */
 static inline int davinci_spi_get_prescale(struct davinci_spi *dspi,
@@ -263,12 +263,13 @@ static inline int davinci_spi_get_prescale(struct davinci_spi *dspi,
 {
        int ret;
 
-       ret = DIV_ROUND_UP(clk_get_rate(dspi->clk), max_speed_hz);
+       /* Subtract 1 to match what will be programmed into SPI register. */
+       ret = DIV_ROUND_UP(clk_get_rate(dspi->clk), max_speed_hz) - 1;
 
-       if (ret < 1 || ret > 256)
+       if (ret < 0 || ret > 255)
                return -EINVAL;
 
-       return ret - 1;
+       return ret;
 }
 
 /**