VR control from the BMC

Ed Tanous edtanous at google.com
Wed Oct 28 07:54:10 AEDT 2020

On Tue, Oct 27, 2020 at 1:26 PM Patrick Williams <patrick at stwcx.xyz> wrote:
> 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
> project.
> 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.
> https://lore.kernel.org/lkml/20191001160407.6265-1-alpawi@amazon.com/

That pointer helps.  Thanks.

> --
> Patrick Williams

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