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authorThomas Koeller <thomas.koeller@baslerweb.com>2010-04-26 05:01:45 -0400
committerGrant Likely <grant.likely@secretlab.ca>2010-05-25 02:23:54 -0400
commit0c2a2ae32793e3500a15a449612485f5d17dd431 (patch)
tree36e31ce3b9f789d6ccc5c273d24a2f149f0e6d2b /drivers/spi/davinci_spi.c
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>
Diffstat (limited to 'drivers/spi/davinci_spi.c')
-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 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,
301 struct davinci_spi *davinci_spi; 301 struct davinci_spi *davinci_spi;
302 struct davinci_spi_platform_data *pdata; 302 struct davinci_spi_platform_data *pdata;
303 u8 bits_per_word = 0; 303 u8 bits_per_word = 0;
304 u32 hz = 0, prescale; 304 u32 hz = 0, prescale = 0, clkspeed;
305 305
306 davinci_spi = spi_master_get_devdata(spi->master); 306 davinci_spi = spi_master_get_devdata(spi->master);
307 pdata = davinci_spi->pdata; 307 pdata = davinci_spi->pdata;
@@ -338,10 +338,16 @@ static int davinci_spi_setup_transfer(struct spi_device *spi,
338 set_fmt_bits(davinci_spi->base, bits_per_word & 0x1f, 338 set_fmt_bits(davinci_spi->base, bits_per_word & 0x1f,
339 spi->chip_select); 339 spi->chip_select);
340 340
341 prescale = ((clk_get_rate(davinci_spi->clk) / hz) - 1) & 0xff; 341 clkspeed = clk_get_rate(davinci_spi->clk);
342 if (hz > clkspeed / 2)
343 prescale = 1 << 8;
344 if (hz < clkspeed / 256)
345 prescale = 255 << 8;
346 if (!prescale)
347 prescale = ((clkspeed / hz - 1) << 8) & 0x0000ff00;
342 348
343 clear_fmt_bits(davinci_spi->base, 0x0000ff00, spi->chip_select); 349 clear_fmt_bits(davinci_spi->base, 0x0000ff00, spi->chip_select);
344 set_fmt_bits(davinci_spi->base, prescale << 8, spi->chip_select); 350 set_fmt_bits(davinci_spi->base, prescale, spi->chip_select);
345 351
346 return 0; 352 return 0;
347} 353}