From: Chen Gong This updates the SPI clock rate calculations for the spi_mpc83xx driver. Some boundary conditions were wrong, and in several cases divide-by-16 wasn't always needed Signed-off-by: Chen Gong Signed-off-by: David Brownell Signed-off-by: Andrew Morton --- drivers/spi/spi_mpc83xx.c | 29 ++++++++++++++++------------- 1 file changed, 16 insertions(+), 13 deletions(-) diff -puN drivers/spi/spi_mpc83xx.c~spi-spi_mpc83xx-clockrate-fixes drivers/spi/spi_mpc83xx.c --- a/drivers/spi/spi_mpc83xx.c~spi-spi_mpc83xx-clockrate-fixes +++ a/drivers/spi/spi_mpc83xx.c @@ -266,21 +266,24 @@ int mpc83xx_spi_setup_transfer(struct sp cs->hw_mode |= SPMODE_LEN(bits_per_word); - if ((mpc83xx_spi->spibrg / hz) >= 64) { - pm = mpc83xx_spi->spibrg / (hz * 64) - 1; - if (pm > 0x0f) { - dev_err(&spi->dev, "Requested speed is too " - "low: %d Hz. Will use %d Hz instead.\n", - hz, mpc83xx_spi->spibrg / 1024); - pm = 0x0f; + if ((mpc83xx_spi->spibrg / hz) > 64) { + pm = mpc83xx_spi->spibrg / (hz * 64); + if (pm > 16) { + cs->hw_mode |= SPMODE_DIV16; + pm /= 16; + if (pm > 16) { + dev_err(&spi->dev, "Requested speed is too " + "low: %d Hz. Will use %d Hz instead.\n", + hz, mpc83xx_spi->spibrg / 1024); + pm = 16; + } } - cs->hw_mode |= SPMODE_PM(pm) | SPMODE_DIV16; - } else { + } else pm = mpc83xx_spi->spibrg / (hz * 4); - if (pm) - pm--; - cs->hw_mode |= SPMODE_PM(pm); - } + if (pm) + pm--; + + cs->hw_mode |= SPMODE_PM(pm); regval = mpc83xx_spi_read_reg(&mpc83xx_spi->base->mode); if (cs->hw_mode != regval) { unsigned long flags; _