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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>
This commit is contained in:
Hannu Heikkinen 2011-02-24 21:31:33 +02:00 committed by Grant Likely
parent 1648237dc2
commit 57d9c10dd9
1 changed files with 18 additions and 11 deletions
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29
drivers/spi/omap2_mcspi.c
View File

@ -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;
}