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authorThomas Koeller <thomas.koeller@baslerweb.com>2010-04-26 09:01:45 +0000
committerGrant Likely <grant.likely@secretlab.ca>2010-05-25 00:23:54 -0600
commit0c2a2ae32793e3500a15a449612485f5d17dd431 (patch)
tree36e31ce3b9f789d6ccc5c273d24a2f149f0e6d2b
parent41c4221ca6b9db8ea63d2c2323c0e7a8865eba6e (diff)
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 <thomas.koeller@baslerweb.com> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
-rw-r--r--drivers/spi/davinci_spi.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/drivers/spi/davinci_spi.c b/drivers/spi/davinci_spi.c
index 95afb6b7739..b85090caf7c 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;
}