VR control from the BMC

Patrick Williams patrick at stwcx.xyz
Wed Oct 28 07:26:34 AEDT 2020

On Mon, Oct 26, 2020 at 04:02:22PM -0700, Ed Tanous wrote:
> In the near future, I'm going to have some needs for OpenBMC to be
> able to control VRs.  These VRs might be on the baseboard itself, or
> on detected PCIe add-in-cards, and controlled over PMBus.
> Additionally, I will need a "hardware safe" way for the host to be
> able to modify the behavior of these VRs (usually different voltage
> settings), and to have that interface be constrained in such a way
> that the host can never set a value that's outside of a predefined
> range that's known to be safe for the hardware, which the BMC will own
> the definition of for security purposes.
> Does anyone else have similar needs?  I've been pointed to
> phosphor-regulators which has some similar parallels;  As-is, that
> solution won't work for me, because it's relying on fixed, platform
> specific json scripting to accomplish its goals.  My hope would be for
> a more generalized linux devicetree based solution, as well as a
> representation on dbus that could be modified at runtime by
> Redfish/IPMI in band.
> Is there any other work I should look into that's similar?  Does
> anyone have any strong opinions on how this should be organized or how
> it could be built?
> Thanks,
> -Ed

Are these PMBus VRs?  I was able to program limits on a non-BMC project
I was working on using the PMBus interfaces to the VRs we used on that

I did need to write this patch which I'm still suppose to clean up with
some additional clamp_val tweaks to avoid negative numbers.


Patrick Williams
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