On Wednesday 11 January 2012 11:12 PM, Shubhrajyoti D wrote: > From: Vikram Pandita <vikram.pandita@xxxxxx> I am reworking the patch on the latest changes. Please ignore this. > In case a peripheral is driving SDA bus low (ie. a start condition), provide > a constant clock output using the test mode of the OMAP I2C controller to > try and clear the bus. Soft reset I2C controller after attempting the bus clear > to ensure that controller is in a good state. > > Based upon Vikram Pandita's patch from TI Android 3.0 kernel and modified for > mainline by Jon Hunter. A couple differences from the original patch ... > 1. Add a new function for bus clear > 2. Ensure that the CON.I2C_EN bit is set when using the SYSTEST feature to > output a permanent clock. This bit needs to be set and tpyically it would > be set by the unidle function but this is not the case for all OMAP > generations. > 3. Program the SYSTEST setting only the bits we care about. However, restore > SYSTEST registers to there original state as some OMAP generations do not > implement perform a soft-reset. > 4. Clear the CON register after performing the bus clear, so when we call the > init function the controller is disabled and the init function will > re-enable later. > > Cc: Kevin Hilman <khilman@xxxxxx> > Signed-off-by: Vikram Pandita <vikram.pandita@xxxxxx> > Signed-off-by: Jon Hunter <jon-hunter@xxxxxx> > Signed-off-by: Shubhrajyoti D <shubhrajyoti@xxxxxx> > --- > Original patch can be found here: > http://git.omapzoom.org/?p=kernel/omap.git;a=commit;h=a2ab04192ba25e60f95ba1ff3af5601a2d7b5bd1 > applies on Kevin's for_3.3/i2c/misc > > drivers/i2c/busses/i2c-omap.c | 32 +++++++++++++++++++++++++++++--- > 1 files changed, 29 insertions(+), 3 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c > index f713eac..6d59bc6 100644 > --- a/drivers/i2c/busses/i2c-omap.c > +++ b/drivers/i2c/busses/i2c-omap.c > @@ -147,16 +147,15 @@ enum { > #define OMAP_I2C_SCLH_HSSCLH 8 > > /* I2C System Test Register (OMAP_I2C_SYSTEST): */ > -#ifdef DEBUG > #define OMAP_I2C_SYSTEST_ST_EN (1 << 15) /* System test enable */ > #define OMAP_I2C_SYSTEST_FREE (1 << 14) /* Free running mode */ > #define OMAP_I2C_SYSTEST_TMODE_MASK (3 << 12) /* Test mode select */ > -#define OMAP_I2C_SYSTEST_TMODE_SHIFT (12) /* Test mode select */ > +#define OMAP_I2C_SYSTEST_TMODE_TEST (2 << 12) /* Test mode select */ > +#define OMAP_I2C_SYSTEST_TMODE_LOOP (3 << 12) /* Test mode select */ > #define OMAP_I2C_SYSTEST_SCL_I (1 << 3) /* SCL line sense in */ > #define OMAP_I2C_SYSTEST_SCL_O (1 << 2) /* SCL line drive out */ > #define OMAP_I2C_SYSTEST_SDA_I (1 << 1) /* SDA line sense in */ > #define OMAP_I2C_SYSTEST_SDA_O (1 << 0) /* SDA line drive out */ > -#endif > > /* OCP_SYSSTATUS bit definitions */ > #define SYSS_RESETDONE_MASK (1 << 0) > @@ -508,6 +507,31 @@ static int omap_i2c_wait_for_bb(struct omap_i2c_dev *dev) > } > > /* > + * Bus Clear > + */ > +static int omap_i2c_bus_clear(struct omap_i2c_dev *dev) > +{ > + u16 w; > + > + /* > + * Per the I2C specification, if we are stuck in a bus busy state > + * we can attempt a bus clear to try and recover the bus by sending > + * at least 9 clock pulses on SCL. Put the I2C in a test mode so it > + * will output a continuous clock on SCL. > + */ > + w = omap_i2c_read_reg(dev, OMAP_I2C_SYSTEST_REG); > + omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, OMAP_I2C_CON_EN); > + omap_i2c_write_reg(dev, OMAP_I2C_SYSTEST_REG, > + (OMAP_I2C_SYSTEST_ST_EN | OMAP_I2C_SYSTEST_TMODE_TEST)); > + msleep(1); > + omap_i2c_write_reg(dev, OMAP_I2C_SYSTEST_REG, w); > + omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, 0); > + omap_i2c_reset(dev); > + omap_i2c_init(dev); > + return omap_i2c_wait_for_bb(dev); > +} > + > +/* > * Low level master read/write transaction. > */ > static int omap_i2c_xfer_msg(struct i2c_adapter *adap, > @@ -632,6 +656,8 @@ omap_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num) > > r = omap_i2c_wait_for_bb(dev); > if (r < 0) > + r = omap_i2c_bus_clear(dev); > + if (r < 0) > goto out; > > if (dev->set_mpu_wkup_lat != NULL) -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
