linux-kernel - Re: [PATCH 0/1] i2c: imc: Add support for Intel iMC SMBus host controller.

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Message-Id: <20200405214059.91F97899799@corona.crabdance.com>
Date:   Sun,  5 Apr 2020 14:40:59 -0700 (PDT)
From:   Stefan Schaeckeler <schaecsn@....net>
To:     wsa@...-dreams.de
CC:     luto@...nel.org, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org, andy.shevchenko@...il.com
Subject: Re: [PATCH 0/1] i2c: imc: Add support for Intel iMC SMBus host
 controller.

Hello Wolfram,

> > > This patch is based on Andy Lutomirski's iMC SMBus driver patch-set
> > > https://lkml.org/lkml/2016/4/28/926. It never made it into the kernel. I hope
> > > this rewrite will:
> > >
> > >
> > > Overview
> > >
> > > Modern Intel memory controllers host an SMBus controller and connection to
> > > DIMMs and their thermal sensors. The memory controller firmware has three modes
> > > of operation: Closed Loop Thermal Throttling (CLTT), Open Loop Thermal
> > > Throttling (OLTT) and none.
> > >
> > > - CLTT: The memory controller firmware is periodically accessing the DIMM
> > >   temperature sensor over the SMBus.
> > >
> >
> >
> > I think this is great!  One question, though: what happens if the
> > system is in CLTT mode but you disable CLTT and claim the bus for too
> > long?  For example, if there's an infinite loop or other lockup which
> > you have the tsod polling interval set to 0?  Does the system catch
> > fire or does the system do something intelligent like temporarily
> > switching to open loop?
>
> Any news on this question?

Thank you for your interest in this patch. You can read my reply here
https://lkml.org/lkml/2020/3/1/216

 Stefan