Hello Sam, On 26.07.23 00:13, Sam Edwards wrote: > The MVTWSI controller can act either as a master or slave device. When > acting as a master, the FSM is driven by the CPU. As a slave, the FSM is > driven by the bus directly. In what is (apparently) a safety mechanism, > if the bus transitions our FSM in any improper way, the FSM goes to a > "bus error" state (0x00). I could find no documented or experimental way > to get the FSM out of this state, except for a controller reset. > > Since U-Boot only uses the MVTWSI controller as a bus master, this > feature only gets in the way: we do not care what happened on the bus > previously as long as the bus is ready for a new transaction. So, when > trying to start a new transaction, check for this state and reset the > controller if necessary. > > Note that this should not be confused with the "deblocking" technique > (used by the `i2c reset` command), which involves pulsing SCL repeatedly > if SDA is found to be held low, in an attempt to force the bus back to > an idle state. This patch only resets the controller in case something > else had previously upset it, and (in principle) results in no > externally-observable change in behavior. > > Signed-off-by: Sam Edwards <cfswo...@gmail.com> > --- > drivers/i2c/mvtwsi.c | 42 ++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 42 insertions(+)
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