On Wed, Apr 24, 2024 at 3:41 PM Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote: > On Wed, Apr 24, 2024 at 12:00 PM Wolfram Sang > <wsa+renesas@xxxxxxxxxxxxxxxxxxxx> wrote: > > On Wed, Apr 24, 2024 at 03:08:14AM +0300, Andy Shevchenko wrote: > > > Wed, Apr 10, 2024 at 01:24:14PM +0200, Wolfram Sang kirjoitti: > > > > While working on another cleanup series, I stumbled over the fact that > > > > some drivers print an error on I2C or SMBus related timeouts. This is > > > > wrong because it may be an expected state. The client driver on top > > > > knows this, so let's keep error handling on this level and remove the > > > > prinouts from controller drivers. > > > > > > > > Looking forward to comments, > > > > > > I do not see an equivalent change in I²C core. > > > > There shouldn't be. The core neither knows if it is okay or not. The > > client driver knows. > > > > > IIRC in our case (DW or i801 or iSMT) we often have this message as the only > > > > Often? How often? > > Once in a couple of months I assume. Last time it was a few weeks ago > that there was a report and they pointed to this very message which > was helpful. > > > > one that points to the issues (on non-debug level), it will be much harder to > > > debug for our customers with this going away. > > > > The proper fix is to print the error in the client driver. Maybe this > > needs a helper for client drivers which they can use like: > > > > i2c_report_error(client, retval, flags); > > > > The other thing which is also more helpful IMO is that we have > > trace_events for __i2c_transfer. There, you can see what was happening > > on the bus before the timeout. It can easily be that, if device X > > times out, it was because of the transfer before to device Y which locks > > up the bus. A simple "Bus timed out" message will not help you a lot > > there. > > The trace events are good to have, not sure if production kernels have > them enabled, though. Ah, and to accent on the usefulness of the message that happens before one thinks about enabling trace events. How usual is that we _expect_ something to fail? Deeper debugging usually happens after we have noticed the issue. I'm not sure if there is an equivalent to signal about a problem without expecting it to happen. Is that -ETIMEDOUT being converted to some message somewhere? > > And, keep in mind the false positives I mentioned in the coverletter. -- With Best Regards, Andy Shevchenko
