RE: [PATCH v2 00/10] i2c: xiic: Add features, bug fixes.

[Raviteja Narayanam]

> -----Original Message-----
> From: Marek Vasut <marex@xxxxxxx>
> Sent: Wednesday, July 21, 2021 3:14 AM
> To: Raviteja Narayanam <rna@xxxxxxxxxx>; Michal Simek
> <michals@xxxxxxxxxx>; linux-i2c@xxxxxxxxxxxxxxx
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; git
> <git@xxxxxxxxxx>; joe@xxxxxxxxxxx
> Subject: Re: [PATCH v2 00/10] i2c: xiic: Add features, bug fixes.
> 
> On 7/20/21 4:19 PM, Raviteja Narayanam wrote:
> 
> Hi,
> 
> [...]
> 
> >>> I have tested this again on our boards with eeprom and other
> >>> sensors, this
> >> is working fine for us.
> >>
> >> Can you share details of how those tests were performed ?
> >
> > Stress test - 1:
> > Heavy ethernet traffic running in the background.
> > I2c commands script (like below) running. We can see visible stutter in the
> output as expected, but nothing failed.
> >
> > i=0
> > while [ 1 ]
> > do
> > 		i2ctransfer -y -f 2 w1@0X54 0X00 r31@0X54
> > 		i2ctransfer -y -f 2 w1@0X54 0X00 r32@0X54
> > 		i2ctransfer -y -f 2 w1@0X54 0X00 r255@0X54
> > 		i2ctransfer -y -f 2 w1@0X54 0X00 r273@0X54
> >                               i2ctransfer -y -f 2 w1@0X54 0X00 r1@0X54
> 
> Could it be that you never see the problem because you always talk to one
> single device ?

There are transfers to other devices as well. 
Our board has multiple power monitors, eeprom and other misc devices that
are accessed through the same driver and are working fine.

> 
> Do you also test writes which are not 1 byte long ?
>

Yes, like for eeprom 1 page (16 bytes)  is written.
 
> >          i=$(expr $i + 1)
> >          echo "$i"
> > done
> >
> > Stress test - 2:
> > Two i2c scripts running in parallel with commands as shown above with
> different bus numbers (as a result of mux), but going into same XIIC adapter.
> > This is also working fine.
> 
> Could it be the i2c-dev serializes each of those transfers , so no race can be
> triggered ?
> 

Yes, that is true because all our tests are going through the i2c-core only
and there is a lock at adapter level in the core.
It has to be reproducible through the i2c standard interface, which is not
happening at our setup.

I can take your patches that are targeted for this issue, rebase, test
and send them.

Regards,
Raviteja N