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

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Date:   Mon, 26 Jul 2021 15:12:44 +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 7/26/21 7:26 AM, 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 ?
> 
> There are transfers to other devices as well.

The above test only accesses device at address 0x54, right ?

> Our board has multiple power monitors, eeprom and other misc devices that
> are accessed through the same driver and are working fine.

That does not seem to be what the test above does .

>> Do you also test writes which are not 1 byte long ?
>>
> 
> Yes, like for eeprom 1 page (16 bytes)  is written.

I suspect the atmel mxt does much longer writes, try 255 bytes or so.

>>>           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.

I think you and Michal talked about getting the atmel mxt touchscreen, 
so you can test that yourself as well.