Re: [BUG] hwmon: (spd5118) resume fails -ENXIO on write protected hubs

[Armin Wolf <W_Armin@gmx.de>]

Am 18.08.26 um 05:50 schrieb Armin Wolf:

> Am 18.08.26 um 02:11 schrieb Guenter Roeck:
>
>> On 8/17/26 16:02, Armin Wolf wrote:
>>> Am 17.08.26 um 19:03 schrieb GG:
>>>
>>>> Understood - thanks for explaining the page selection part, that 
>>>> makes sense. I'll blacklist it for now.
>>>>
>>>> Appreciate you taking the time to get back to me on this!
>>>>
>>>> Gabriel G
>>>>
>>>> On Monday, August 17th, 2026 at 12:58 PM, Guenter Roeck 
>>>> <linux@roeck-us.net> wrote:
>>>>
>>>>> On 8/17/26 09:42, GG wrote:
>>>>>> Sorry - I should have searched the archives before sending my 
>>>>>> last email. I've since
>>>>>> found this from February, which is the same problem:
>>>>>>
>>>>>> https://lore.kernel.org/linux-hwmon/20260205102942.28745-1-tinsaetadesse2015@gmail.com/ 
>>>>>>
>>>>>>
>>>>>> And I missed the obvious clue sitting in my own boot log:
>>>>>>
>>>>>>     i801_smbus 0000:00:1f.4: SPD Write Disable is set
>>>>>>
>>>>>> So my kernel already knew. Apologies for the noise.
>>>>>>
>>>>> Unfortunately that knowledge is not passed on to the spd5118 driver.
>>>
>>> Yes, sadly the patch series adding support for this was abandoned :/
>>>
>>
>> If I recall correctly, the important part (a 
>> I2C_AQ_SPD_WRITE_DISABLED flag
>> or similar provided by the I2C controller) was rejected. 
>
> What? I seemed to have missed that important info. How frustrating.
>
>>>>>> One thing I'll mention in case it's useful: that series above has 
>>>>>> spd5118 refuse to
>>>>>> probe when writes are disabled. On my machine that would lose me 
>>>>>> two working
>>>>>> temperature sensors. Reads are completely fine here, I get 
>>>>>> correct temps,
>>>>>> and my temperature limits read back properly. It's only writing 
>>>>>> that fails.
>>>>>>
>>>>>> Happy to test anything on my hardware if it would help.
>>>>>>
>>>>> That can not be done, as I mentioned in my other e-mail.
>>>>>
>>>>> Problem is that accessing temperature sensor data on spd5118 
>>>>> compatible chips
>>>>> requires a write to select the correct chip page. If writes are 
>>>>> disabled, and
>>>>> the BIOS selected a page other than page 0, temperature sensor 
>>>>> data is not
>>>>> accessible. Since the BIOS can do whatever it wants and may have 
>>>>> selected a
>>>>> different page after a suspend/resume sequence, one simply can not 
>>>>> trust
>>>>> the status when the driver is loaded initially.
>>>>>
>>>>> Guenter
>>>
>>> Would it be enough if we always select page 0 inside 
>>> spd5118_i2c_init(), thereby
>>> preventing the driver from probing on hardware that does not allow 
>>> us to write
>>> the page select register?
>>>
>>
>> Looking into the code, it seems like the device may have been 
>> instantiated
>> through the detect path. That makes me wonder which distribution enables
>> CONFIG_SENSORS_SPD5118_DETECT because it should _not_ be enabled by 
>> default.
>>
>> Anyway, I guess I'll have to implement a dummy write operation in
>> spd5118_i2c_init() to check if writes are possible and bail out on 
>> error.
>> That is less than perfect but the best we can do without a flag from the
>> I2C controller.
>>
>> I'll look into that after the commit window closes.
>>
>> Thanks,
>> Guenter
>
> I already have prepared two patches for that, i will test them on my 
> machine as soon as possible.
>
> Thanks,
> Armin Wolf 

Both patches seems to work, but i do not have an DDR5-based Intel system and hand. Still, do you want
me to send those patches when the new merge window opens?

Thanks,
Armin Wolf