i2c-tools does not work with AMD Cezanne APU's

i2c-tools does not work with AMD Cezanne APU's

[Jon P]

After updating to a 5700G APU from a 2400G on my B450 board I am not
able to access i2c interfaces which is a blocking issue to use OpenRGB
on the DRAM and motherboard RGB controller (I am one of the developers
of OpenRGB).

I have opened an issue with the distribution that I am using and
multiple other users are seeing the same issue but I have not seen any
updates on the issue or request for more details so I am afraid that
it has just gone into the void. Full details here:
https://bugs.launchpad.net/bugs/1950062

I see the same issues when using the i2c-tools as well when I am
trying to read the DRAM so following the man page I would like to
report a bug using the i2c-tools with AMD Cezanne APU's.

Thanks for looking into this.

Regards, TheRogueZeta

Re: i2c-tools does not work with AMD Cezanne APU's

[Jean Delvare]

Hi Jon,

On Tue, 18 Jan 2022 17:26:03 -0800, Jon P wrote:
> After updating to a 5700G APU from a 2400G on my B450 board I am not
> able to access i2c interfaces which is a blocking issue to use OpenRGB
> on the DRAM and motherboard RGB controller (I am one of the developers
> of OpenRGB).
> 
> I have opened an issue with the distribution that I am using and
> multiple other users are seeing the same issue but I have not seen any
> updates on the issue or request for more details so I am afraid that
> it has just gone into the void. Full details here:
> https://bugs.launchpad.net/bugs/1950062
> 
> I see the same issues when using the i2c-tools as well when I am
> trying to read the DRAM so following the man page I would like to
> report a bug using the i2c-tools with AMD Cezanne APU's.

From your logs, the i2c bus itself is not working. So this is
definitely not an i2c-tools issue, but a kernel driver issue.

Most likely this is related to the required change of register access
method for recent AMD chipsets which has been discussed recently:

https://lore.kernel.org/linux-i2c/20220118221152.300444-1-terry.bowman@amd.com/T/#t

-- 
Jean Delvare
SUSE L3 Support