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| author | Hannu Heikkinen <ext-hannu.m.heikkinen@nokia.com> | 2011-02-24 21:31:33 +0200 |
|---|---|---|
| committer | Grant Likely <grant.likely@secretlab.ca> | 2011-02-24 12:44:37 -0700 |
| commit | 57d9c10dd91f942f836592f407d6351e2969548a (patch) | |
| tree | 38ffc12947c93bf96de66b88d4c719913e0477f0 /drivers/spi | |
| parent | 1648237dc2053bfd6ade3ce3dca3716d53cf9dcf (diff) | |
| download | linux-57d9c10dd91f942f836592f407d6351e2969548a.tar.gz linux-57d9c10dd91f942f836592f407d6351e2969548a.tar.bz2 linux-57d9c10dd91f942f836592f407d6351e2969548a.zip | |
spi/omap_mcspi: Off-by-one error in finding the right divisor
Off-by-one error, gave erroneous divisor value 16 if speed_hz is over zero but
less than OMAP2_MCSPI_MAX_FREQ / (1 << 15), that is, [1..1463].
Also few overly complex bit shifts in divisor fixed.
Also one dev_dgb line fixed, which indicated max speed exceeding transfer speed.
Introducing a new function omap2_mcspi_calc_divisor() for getting the right
divisor in omap2_mcspi_setup_transfer().
Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Signed-off-by: Hannu Heikkinen <ext-hannu.m.heikkinen@nokia.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Diffstat (limited to 'drivers/spi')
| -rw-r--r-- | drivers/spi/omap2_mcspi.c | 29 |
1 files changed, 18 insertions, 11 deletions
diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c index abb1ffbf3d20..1a2d0b8bdd6a 100644 --- a/drivers/spi/omap2_mcspi.c +++ b/drivers/spi/omap2_mcspi.c @@ -651,6 +651,17 @@ out: return count - c; } +static u32 omap2_mcspi_calc_divisor(u32 speed_hz) +{ + u32 div; + + for (div = 0; div < 15; div++) + if (speed_hz >= (OMAP2_MCSPI_MAX_FREQ >> div)) + return div; + + return 15; +} + /* called only when no transfer is active to this device */ static int omap2_mcspi_setup_transfer(struct spi_device *spi, struct spi_transfer *t) @@ -673,12 +684,8 @@ static int omap2_mcspi_setup_transfer(struct spi_device *spi, if (t && t->speed_hz) speed_hz = t->speed_hz; - if (speed_hz) { - while (div <= 15 && (OMAP2_MCSPI_MAX_FREQ / (1 << div)) - > speed_hz) - div++; - } else - div = 15; + speed_hz = min_t(u32, speed_hz, OMAP2_MCSPI_MAX_FREQ); + div = omap2_mcspi_calc_divisor(speed_hz); l = mcspi_cached_chconf0(spi); @@ -715,7 +722,7 @@ static int omap2_mcspi_setup_transfer(struct spi_device *spi, mcspi_write_chconf0(spi, l); dev_dbg(&spi->dev, "setup: speed %d, sample %s edge, clk %s\n", - OMAP2_MCSPI_MAX_FREQ / (1 << div), + OMAP2_MCSPI_MAX_FREQ >> div, (spi->mode & SPI_CPHA) ? "trailing" : "leading", (spi->mode & SPI_CPOL) ? "inverted" : "normal"); @@ -1015,10 +1022,10 @@ static int omap2_mcspi_transfer(struct spi_device *spi, struct spi_message *m) t->bits_per_word); return -EINVAL; } - if (t->speed_hz && t->speed_hz < OMAP2_MCSPI_MAX_FREQ/(1<<16)) { - dev_dbg(&spi->dev, "%d Hz max exceeds %d\n", - t->speed_hz, - OMAP2_MCSPI_MAX_FREQ/(1<<16)); + if (t->speed_hz && t->speed_hz < (OMAP2_MCSPI_MAX_FREQ >> 15)) { + dev_dbg(&spi->dev, "speed_hz %d below minimum %d Hz\n", + t->speed_hz, + OMAP2_MCSPI_MAX_FREQ >> 15); return -EINVAL; } |