On 11/25/10 14:24, Sebastian Andrzej Siewior wrote: > Igor Grinberg wrote: >> Hi, > Hi, > >>>> Even you reset I2C controller, it shouldn't help you since bus isn't >>>> free. I thinkt that you should reset I2C bus before you reseting I2C >>>> controller. > > According to the register, IBB (bus busy) is cleared at this point. The > only remaining flag is UB (unit busy) and RW mode. > >>> Excuse me that my previous comments are for PXA master mode. > I am in master mode. > >>> I think that you're focused on pxa working on slave mode. But if pxa >>> is working in master mode, it seems that we needn't reset I2C >>> controller since it doesn't help. >> >> As for PXA3xx, the Developer Manual states: >> "Software must ensure that the TWSI unit is not busy (ISR[UB] = 0) >> before it asserts a reset. Software must also ensure that the TWSI bus is idle (ISR[IBB] = 0) >> when the unit is enabled after reset." > > My manual says more or less the same thing. It says "unit not busy" but > quotes the IBB bit in braces. It is probably a typo. > The register say: ISR=00000005, ICR=000017e0, IBMR=01 > So according to this I am not allowed to reset the I2C unit while it is > busy. > > I tracked it down to the following: i2cdetect tries to read a byte from > address 47. This fails because there is no device. Then it goes for 48 > which returns 0 (there is a device). The following read always fails. So I > guess the device at 48 is still sending data. What is general rule of > thumb in such a case? I don't think there is such a rule for this case, as if we "believe" the Developer Manual, but do the opposite - we can get into trouble... IMHO, at least we need to report a problem. Or may be in some way reset the slave device, if there is such an option available outside the i2c scope... (Yeah, I know this is a crazy idea...) > >>> From my experience, in master mode resetting the controller >> does not help and if the bus is busy for too much time, >> there always was a h/w problem involved. > > Looks like it. 1) Well, you should check if you have a pull-up resistors on that bus. 2) Or if the slave device chip is broken, then it should be replaced. > > Sebastian > -- Regards, Igor. -- 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
