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

[Armin Wolf <W_Armin@gmx.de>]

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