Hi Phil, yes, this thread is old but a similar issue came up again... On Fri, Oct 25, 2019 at 09:14:00AM +0800, Phil Reid wrote: > > > > > So at the beginning of a new transfer, we should check if SDA (or SCL?) > > > is low and, if it's true, only then we should try recover the bus. > > > > Yes, this is the proper time to do it. Remember, I2C does not define a > > timeout. > > > > FYI: Just a single poll at the start of the transfer, for it being low, will cause problems with multi-master buses. > Bus recovery should be attempted after a timeout when trying to communicate, even thou i2c doesn't define a timeout. > > I'm trying to fix the designware drivers handling of this at the moment. I wonder what you ended up with? You are right, a single poll is not enough. It only might be if one applies the new "single-master" binding for a given bus. If that is not present, my best idea so far is to poll SDA for the time defined in adapter->timeout and if it is all low, then initiate a recovery. All the best, Wolfram
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