On Wed, Jul 08, 2015 at 04:35:27PM +0200, Jan Luebbe wrote: > At least on the AM335x, enabling OMAP_I2C_SYSTEST_ST_EN is not enough to Felipe: it seems you did not need this; is this AM335x specific? > allow direct access to the SCL and SDA pins. In addition to ST_EN, we > need to set the TMODE to 0b11 (Loop back & SDA/SCL IO mode select). > Also, as the reset values of SCL_O and SDA_O are 0 (which means "drive > low level"), we need to set them to 1 (which means "high-impedance") to > avoid unwanted changes on the pins. > > As a precaution, reset all these bits to their default values after > recovery is complete. > > Signed-off-by: Jan Luebbe <jlu@xxxxxxxxxxxxxx> > --- > drivers/i2c/busses/i2c-omap.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c > index d1c22e3fdd14..fc9bf7f30e35 100644 > --- a/drivers/i2c/busses/i2c-omap.c > +++ b/drivers/i2c/busses/i2c-omap.c > @@ -1247,7 +1247,14 @@ static void omap_i2c_prepare_recovery(struct i2c_adapter *adap) > u32 reg; > > reg = omap_i2c_read_reg(dev, OMAP_I2C_SYSTEST_REG); > + /* enable test mode */ > reg |= OMAP_I2C_SYSTEST_ST_EN; > + /* select SDA/SCL IO mode */ > + reg |= 3 << OMAP_I2C_SYSTEST_TMODE_SHIFT; > + /* set SCL to high-impedance state (reset value is 0) */ > + reg |= OMAP_I2C_SYSTEST_SCL_O; > + /* set SDA to high-impedance state (reset value is 0) */ > + reg |= OMAP_I2C_SYSTEST_SDA_O; > omap_i2c_write_reg(dev, OMAP_I2C_SYSTEST_REG, reg); > } > > @@ -1257,7 +1264,11 @@ static void omap_i2c_unprepare_recovery(struct i2c_adapter *adap) > u32 reg; > > reg = omap_i2c_read_reg(dev, OMAP_I2C_SYSTEST_REG); > + /* restore reset values */ > reg &= ~OMAP_I2C_SYSTEST_ST_EN; > + reg &= ~OMAP_I2C_SYSTEST_TMODE_MASK; > + reg &= ~OMAP_I2C_SYSTEST_SCL_O; > + reg &= ~OMAP_I2C_SYSTEST_SDA_O; > omap_i2c_write_reg(dev, OMAP_I2C_SYSTEST_REG, reg); > } > > -- > 2.1.4 >
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