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authorHannu Heikkinen <ext-hannu.m.heikkinen@nokia.com>2011-02-24 21:31:33 +0200
committerGrant Likely <grant.likely@secretlab.ca>2011-02-24 12:44:37 -0700
commit57d9c10dd91f942f836592f407d6351e2969548a (patch)
tree38ffc12947c93bf96de66b88d4c719913e0477f0 /drivers/spi
parent1648237dc2053bfd6ade3ce3dca3716d53cf9dcf (diff)
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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>
Diffstat (limited to 'drivers/spi')
-rw-r--r--drivers/spi/omap2_mcspi.c29
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;
}