| Message ID | 1436366127-24756-1-git-send-email-jlu@pengutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 08/07/15 16:35, Jan Luebbe wrote: > At least on the AM335x, enabling OMAP_I2C_SYSTEST_ST_EN is not enough to > 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@pengutronix.de> Tested with oscilloscope on Beagle Bone Black, without the patch nothing meningful appears on SCL during recovery, with the patch I'm able to see the recovery pulses. Tested-by: Alexander Sverdlin <alexander.sverdlin@gmail.com> > --- > 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); > }
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@pengutronix.de> > --- > 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 >
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 <grygorii.strashko@ti.com> >> >> Signed-off-by: Jan Luebbe <jlu@pengutronix.de> >> --- >> 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 >>
On Tue, Jul 14, 2015 at 03:10:01PM +0300, Grygorii Strashko wrote: > 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). So, how did it work for him? > It's not AM335x specific. TMODE has to be configured for all OMAP4+ SoCs too. Okay, thanks for the stepping in!
On Di, 2015-07-14 at 14:12 +0200, Wolfram Sang wrote: > On Tue, Jul 14, 2015 at 03:10:01PM +0300, Grygorii Strashko wrote: > > 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). > > So, how did it work for him? > > > It's not AM335x specific. TMODE has to be configured for all OMAP4+ SoCs too. > > Okay, thanks for the stepping in! Wolfram, will you pick this as-is? Regards, Jan
On Wed, Jul 29, 2015 at 12:27:30PM +0200, Jan Lübbe wrote: > On Di, 2015-07-14 at 14:12 +0200, Wolfram Sang wrote: > > On Tue, Jul 14, 2015 at 03:10:01PM +0300, Grygorii Strashko wrote: > > > 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). > > > > So, how did it work for him? > > > > > It's not AM335x specific. TMODE has to be configured for all OMAP4+ SoCs too. > > > > Okay, thanks for the stepping in! > > Wolfram, will you pick this as-is? Yes, I was hoping for an answer to my above question to get a better understanding, but we can still apply the patches meanwhile.
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 > 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@pengutronix.de> Applied to for-current, thanks!
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); }
At least on the AM335x, enabling OMAP_I2C_SYSTEST_ST_EN is not enough to 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@pengutronix.de> --- drivers/i2c/busses/i2c-omap.c | 11 +++++++++++ 1 file changed, 11 insertions(+)