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Commit 57d9c10d authored by Hannu Heikkinen's avatar Hannu Heikkinen Committed by Grant Likely
Browse files

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: default avatarPhil Carmody <ext-phil.2.carmody@nokia.com>
Signed-off-by: default avatarHannu Heikkinen <ext-hannu.m.heikkinen@nokia.com>
Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
parent 1648237d

drivers/spi/omap2_mcspi.c

+18 −11
Original line number Diff line number Diff line
@@ -651,6 +651,17 @@ omap2_mcspi_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer) 
	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",

		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/(1<<16));

				OMAP2_MCSPI_MAX_FREQ >> 15);

			return -EINVAL;

		}