Re: ee1004: DDR4 SPD cannot be read, decode-dimms fails, “Failed to select page 0 (-6)”

[Jean Delvare <jdelvare@suse.de>]

On Sun, 30 Aug 2026 17:35:57 +0200, Al Ma wrote:
> > Please try unloading the ee1004 driver, then running i2cdetect again.  
> 
> Here we go:
> 
> # modprobe -r ee1004 && i2cdetect -y 0 && modprobe ee1004
>       0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
> 00:                         08 -- -- -- -- -- -- --
> 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 40: -- -- -- -- 44 -- -- -- -- -- -- -- -- -- -- --
> 50: -- -- -- -- -- -- 56 -- -- -- -- -- -- -- -- --
> 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 70: -- -- -- -- -- -- -- --
> 
> What next?

This confirms my guess that the device at 0x56 is not an SPD EEPROM.
Next steps would be as follows:

* Short term, you want to blacklist the ee1004 driver on your system.
  It is not a good idea to load a driver which binds to the wrong
  device.

* Still short term, we should look into the ee1004 auto-detection logic
  and see it it can be made more reliable.

* Mid term, we may want to add a kernel option to disable automatic
  probing of SPD EEPROMs. I seem to recall some proposals but it looks
  like they never made it into the upstream kernel. I'm not sure if
  this should be a system-wide switch (handled by the i2c core) or a
  per-driver setting (e.g. a new flag in i2c-i801's disable_features
  parameter).

* Still mid term, we probably want to blacklist SPD probing explicitly
  for your motherboard (we'll need to know the contents of
  /sys/devices/virtual/dmi/id/board_vendor and
  /sys/devices/virtual/dmi/id/board_name on your system). Maybe this
  can be implemented as an empty entry in mux_dmi_table (as in, we know
  the board requires multiplexing, but we don't know yet to implement
  it on that board).

* Long term, we need the hardware vendor to provide technical
  information about the board so that we can implement SMBus
  multiplexing support in the i2c-i801 driver (if that's really how
  things are implemented on your board - that's only a guess from me at
  this point). Asus provided information about their Z8 series long ago
  and I was able to add support for it back then. It would be wonderful
  if they could provide similar information about the WS C422 PRO/SE so
  that a kernel developer can add support.

-- 
Jean Delvare
SUSE L3 Support