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Date: Wed, 24 Apr 2024 11:00:53 +0200
From: Wolfram Sang <wsa+renesas@sang-engineering.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, 
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Subject: Re: [PATCH 00/18] i2c: remove printout on handled timeouts
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Hi Andy,

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.
> >=20
> > Looking forward to comments,
>=20
> I do not see an equivalent change in I=C2=B2C 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 o=
nly

Often? How often?

> one that points to the issues (on non-debug level), it will be much harde=
r 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.

And, keep in mind the false positives I mentioned in the coverletter.

All the best,

   Wolfram


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