linux-kernel - Re: [Bug Report] [6.6] i2c: No atomic i2c transfer handler

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Message-ID: <6fb5d126-1c66-412a-a1a2-6c4e5725f7fb@mailbox.org>
Date:   Fri, 1 Dec 2023 13:26:08 +0100
From:   Tor Vic <torvic9@...lbox.org>
To:     Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-i2c@...r.kernel.org
Cc:     benjamin.bara@...data.com
Subject: Re: [Bug Report] [6.6] i2c: No atomic i2c transfer handler



On 12/1/23 12:50, Dmitry Osipenko wrote:
> On 12/1/23 13:48, Tor Vic wrote:
>> Hi,
>>
>> Since Linux 6.6.3, I see some warnings in the late phase of shutdown.
>> Unfortunately, they are not logged because syslog has already shut down
>> at that point.
>>
>> I used a camera to capture a small part of the warnings:
>>
>>    No atomic I2C transfer handler for 'i2c-0'
>>    [trace follows]
>>    i2c_smbus_xfer
>>    [...]
>>
>> After checking the changelog, the culprit was found quickly:
>>
>>    (3473cf43b) i2c: core: Run atomic i2c xfer when !preemptible
>>
>> Reverting that commit made the warnings go away.
>>
>> This is a voluntary preemption kernel running on a Skylake laptop.
>>
>> Please tell me if you need more info.
> 
> The warning says that I2C bus driver used by your laptop doesn't support
> atomic transfers while it should. Which driver it is?

'i2c-0' is
SMBus [0c05]: Intel Corporation Sunrise Point-LP SMBus
using 'i801_smbus' driver.

> 
> In your case the warning is harmless, still the I2C driver likely needs
> to be improved.
> 

That's good news, I was a little worried because of the several (I think 
it was 3 in total) large warning splats.