linux-kernel - Re: [PATCH v2 00/10] i2c: xiic: Add features, bug fixes.

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Message-ID: <328f6c4e-ff0b-c88f-d246-75b493b67a9a@denx.de>
Date:   Tue, 20 Jul 2021 23:43:54 +0200
From:   Marek Vasut <marex@...x.de>
To:     Raviteja Narayanam <rna@...inx.com>,
        Michal Simek <michals@...inx.com>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
Cc:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        git <git@...inx.com>, "joe@...ches.com" <joe@...ches.com>
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@...4 0X00 r31@...4
> 		i2ctransfer -y -f 2 w1@...4 0X00 r32@...4
> 		i2ctransfer -y -f 2 w1@...4 0X00 r255@...4
> 		i2ctransfer -y -f 2 w1@...4 0X00 r273@...4
>                               i2ctransfer -y -f 2 w1@...4 0X00 r1@...4

Could it be that you never see the problem because you always talk to 
one single device ?

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

>          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 ?

> Stress test - 3:
> Two i2c scripts running in parallel with same commands in separate terminals. This is also working fine.
> 
>  From your log, the race condition is occurring at boot time during i2c clients registration. I am starting a similar test at my setup
> to reproduce this issue at boot time.

Thank you