Re: [decode-dimms] fails to read SPD

Re: [decode-dimms] fails to read SPD

[Jean Delvare]

Hi Jakob,

On Sun, 3 Oct 2021 09:47:18 +0200, J88 wrote:
> i am trying to read out the DDR4 Specs on
> 
> SETUP
> 
> [Mainboard] Supermicro X10DRH-CT (
> https://www.supermicro.com/en/products/motherboard/X10DRH-CT)
> 
> [Memory]
> 2x 16GB DDR4Super Talent F24R16G4S1
> 
> [OS]
> Ubuntu Server 21.04 / Kernel 5.11.0-37-generic
> 
> --------------------------------
> 
> root@ramtest1:/home/rt1# modprobe -r eeprom
> root@ramtest1:/home/rt1# modprobe ee1004
> root@ramtest1:/home/rt1# i2cdetect -y 1
> 
>      0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
> 00:                         -- -- -- -- -- -- -- --
> 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 30: -- -- -- -- -- -- -- 37 -- -- -- -- -- -- -- --
> 40: -- -- -- -- -- -- -- -- -- 49 -- -- -- -- -- --
> 50: 50 -- -- -- -- -- -- -- -- 59 -- -- -- -- -- --
> 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
> 70: -- -- -- -- -- -- -- --
> 
> root@ramtest1:/home/rt1# echo ee1004 0x50 >
> /sys/bus/i2c/devices/i2c-1/new_device
> root@ramtest1:/home/rt1# echo ee1004 0x59 >
> /sys/bus/i2c/devices/i2c-1/new_device
> root@ramtest1:/home/rt1# decode-dimms
> Cannot read /sys/bus/i2c/drivers/ee1004/1-0050/eeprom at
> /usr/bin/decode-dimms line 2459.

This is a server board with 16 memory slots, well above the 4 supported
by the automatic SPD detection currently implemented in the i2c-i801
driver. These server boards have their SMBus multiplexed, so automatic
DPS detection is not possible. You need to get information from the
vendor, how the multiplexing is implemented. Some boards are using
GPIO-controlled mux chips, and you need to know which pins to toggle.
Other boards use I2C-controlled mux chips, and you need to know which
model and at which address it lives.

This work was already done for Asus Z8 board series 10 years ago. You
will need similar work for your board in order to be able to access SPD
EEPROMs (and possibly some thermal sensors) on your system.

-- 
Jean Delvare
SUSE L3 Support