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

[Armin Wolf]

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@xxxxxxxxxxxx> 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@xxxxxxxxx/
> > >
> > > 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 :/

> > > 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?

Thanks,
Armin Wolf