Hi Krzysztof: * Krzysztof Halasa <khc at pm.waw.pl> [2006-06-06 18:58:46 +0200]: > Another thing: I noticed the i2c_bit_add_bus doesn't set SDA and SCL > lines to a known levels. If the hw driver set them to 1 all is fine > and the first START condition is detected correctly. But if they're > set differently (for example, if both are zero), the START will not > work. > > I'm not sure if the following patch isn't an overkill, though, and > if the lack of initialization is a real problem which shows in > practice and not only on my analyzer. > > In case you think it's needed: > > This patch makes i2c_bit_add_bus() initialize SDA and SCL lines > as required by subsequent START condition. > > Signed-off-by: Krzysztof Halasa <khc at pm.waw.pl> > > --- a/drivers/i2c/algos/i2c-algo-bit.c > +++ b/drivers/i2c/algos/i2c-algo-bit.c > @@ -544,6 +544,13 @@ int i2c_bit_add_bus(struct i2c_adapter * > adap->timeout = 100; /* default values, should */ > adap->retries = 3; /* be replaced by defines */ > > + setsda(bit_adap, 0); /* may mean START if SCL = 1 */ > + udelay(bit_adap->udelay); > + setscl(bit_adap, 1); /* may clock a zero bit in */ > + udelay(bit_adap->udelay); > + setsda(bit_adap, 1); /* STOP */ > + udelay(bit_adap->udelay); > + > i2c_add_adapter(adap); > return 0; > } NACK. The I2C bus spec says[1]: A START condition immediately followed by a STOP condition (void message) is an illegal format. SCL and SDA must be pulled high by hardware. If a driver inits to setting them low, that's a bug in the driver. [1] (page 14, note 5) http://www.semiconductors.philips.com/acrobat_download/literature/9398/39340011.pdf Regards, -- Mark M. Hoffman mhoffman at lightlink.com
