Hi Wolfram, On 07/14/2015 02:10 PM, Wolfram Sang wrote: > 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?
We need it (Felipe's reply can be delayed). It's not AM335x specific. TMODE has to be configured for all OMAP4+ SoCs too. > >> 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. Reviewed-by: Grygorii Strashko <[email protected]> >> >> Signed-off-by: Jan Luebbe <[email protected]> >> --- >> 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 >> -- regards, -grygorii -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
