From 0c2a2ae32793e3500a15a449612485f5d17dd431 Mon Sep 17 00:00:00 2001 From: Thomas Koeller Date: Mon, 26 Apr 2010 09:01:45 +0000 Subject: spi/davinci: Fix clock prescale factor computation Computation of the clock prescaler value returned bogus results if the requested SPI clock was impossible to set. It now sets either the maximum or minimum clock frequency, as appropriate. Signed-off-by: Thomas Koeller Signed-off-by: Grant Likely --- drivers/spi/davinci_spi.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'drivers') diff --git a/drivers/spi/davinci_spi.c b/drivers/spi/davinci_spi.c index 95afb6b77395..b85090caf7cf 100644 --- a/drivers/spi/davinci_spi.c +++ b/drivers/spi/davinci_spi.c @@ -301,7 +301,7 @@ static int davinci_spi_setup_transfer(struct spi_device *spi, struct davinci_spi *davinci_spi; struct davinci_spi_platform_data *pdata; u8 bits_per_word = 0; - u32 hz = 0, prescale; + u32 hz = 0, prescale = 0, clkspeed; davinci_spi = spi_master_get_devdata(spi->master); pdata = davinci_spi->pdata; @@ -338,10 +338,16 @@ static int davinci_spi_setup_transfer(struct spi_device *spi, set_fmt_bits(davinci_spi->base, bits_per_word & 0x1f, spi->chip_select); - prescale = ((clk_get_rate(davinci_spi->clk) / hz) - 1) & 0xff; + clkspeed = clk_get_rate(davinci_spi->clk); + if (hz > clkspeed / 2) + prescale = 1 << 8; + if (hz < clkspeed / 256) + prescale = 255 << 8; + if (!prescale) + prescale = ((clkspeed / hz - 1) << 8) & 0x0000ff00; clear_fmt_bits(davinci_spi->base, 0x0000ff00, spi->chip_select); - set_fmt_bits(davinci_spi->base, prescale << 8, spi->chip_select); + set_fmt_bits(davinci_spi->base, prescale, spi->chip_select); return 0; } -- cgit v1.2.2