linux-kernel - Re: [EXTERNAL] Re: Potential issue with smb word operations for tmp461 device in tmp401 driver

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Message-ID: <7be30cc3-f67d-351f-cce9-94952bc4405d@roeck-us.net>
Date:   Fri, 15 Oct 2021 20:31:37 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     "Wilson, David T. (GSFC-5870)" <david.wilson@...a.gov>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>
Subject: Re: [EXTERNAL] Re: Potential issue with smb word operations for
 tmp461 device in tmp401 driver

On 10/15/21 7:33 PM, Wilson, David T. (GSFC-5870) wrote:
> On my target platform, I do not believe the i2c-tools are completely supported, so i2c-dump is unable to provide me a register dump for the connected tmp461.
> 

No problem. That means though that I won't be able to run a module test,
and I'll have to wait for you or someone else to test my patch
before I can apply it.

Thanks,
Guenter

> If you have any other suggested methods of achieving the i2c register dump, I could try those as well.
> 
> I see on a different email chain that you have already submitted a patch to resolve this tmp461 issue.
> 
> Thanks for looking into this issue!
> David
> 
> 
> From: Guenter Roeck <groeck7@...il.com> on behalf of Guenter Roeck <linux@...ck-us.net>
> Sent: Friday, October 15, 2021 6:27 PM
> To: Wilson, David T. (GSFC-5870) <david.wilson@...a.gov>
> Cc: linux-kernel@...r.kernel.org <linux-kernel@...r.kernel.org>; linux-hwmon@...r.kernel.org <linux-hwmon@...r.kernel.org>
> Subject: [EXTERNAL] Re: Potential issue with smb word operations for tmp461 device in tmp401 driver
>   
> Hi,
> 
> On Fri, Oct 15, 2021 at 05:43:54PM +0000, Wilson, David T. (GSFC-5870) wrote:
>> Hi,
>>
>> I am reporting what I believe is a potential issue in the tmp401 driver for the tmp461 device specifically. I am new to reporting issues, so I apologize in advance if I've provided insufficient information for an issue report.
>>
>> The problem I'm encountering is that when I use the tmp401 linux driver to read temperature values from the tmp461, all of the read temperature values end with 996 (e.g. 33996, 38996, etc...).
>>
>> Looking further into the tmp401 commit messages, I see that the driver was changed to use smb word operations instead of separate byte operations. Although the other supported devices (i.e. tmp432, etc...) are noted to support 16-bit read operations in their respective datasheets, I see no indications of 16-bit read support in the tmp461 datasheet, which is supported by my inquiry in the TI forums (https://gcc02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fe2e.ti.com%2Fsupport%2Fsensors-group%2Fsensors%2Ff%2Fsensors-forum%2F1044935%2Ftmp461-linux-driver-support-and-16-bit-temperature-register-reads&amp;data=04%7C01%7Cdavid.wilson%40nasa.gov%7C1d874c8a8c8e471a2c1a08d9902af71b%7C7005d45845be48ae8140d43da96dd17b%7C0%7C0%7C637699336485905564%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=vwnJOlMAKMn752Vw%2F11KA96%2BPwnen22GvuT6fcitMt8%3D&amp;reserved=0).
>>
>> Reverting the driver to the commit before the smb word change, I am then able to read temperature values that do not end only with 996. As a result, I believe that the tmp461 support may be partially broken by the switch to smb word operations.
>>
> 
> Thanks a lot for the report. Can you send me a register dump for the tmp461 ?
> 
> Thanks,
> Guenter
>