|
| From: | Chris Rauer |
| Subject: | Re: [PATCH 0/2] Adds designware i2c module and adds it to virt arm |
| Date: | Wed, 26 Jan 2022 14:01:44 -0800 |
>>> I need to see a pretty strong justification for why we should be
>>> adding new kinds of devices to the virt machine,
>>
>> The designware i2c controller is a very common controller on many
>> ARM SoCs. It has device tree bindings and ACPI bindings which
>> makes it ideal for this platform.
>
>No, I mean, why do we need an i2c controller on the virt
>board at all ?
The use case we are interested in is to enable IPMI SSIF on the arm virt machine which is why I was interested in something with ACPI support. That particular IPMI SSIF enablement patch is not in this series but I think it could be pulled into the series if necessary.
> > >Forgot to mention, but my prefered approach for providing
> > >an i2c controller on the virt board would be to have a
> > >PCI i2c controller: that way users who do need it can plug it
> > >in with a -device command line option, and users who don't
> > >need it never have to worry about it.
>
> > > (We seem to have an ICH9-SMB PCI device already; I have no idea if it's suitable.)
> > I didn't find that device suitable because it is part of the Intel
> > Southbridge, which may have some Intel platform quirks, and
> > we don't need all the things in that IO hub.
>
> That's a pity. Is there a different PCI I2C controller we could model ?
I’m not aware of any standalone PCI I2C controllers. I’ve seen I2C controllers on PCI devices with other things but I don’t think those could be used for IPMI SSIF or other general I2C use cases. Do you know of a particular device I should take a look at?
-Chris
On Wed, 26 Jan 2022 at 17:12, Chris Rauer <crauer@google.com> wrote:
>
>> I need to see a pretty strong justification for why we should be
>> adding new kinds of devices to the virt machine,
>
> The designware i2c controller is a very common controller on many
> ARM SoCs. It has device tree bindings and ACPI bindings which
> makes it ideal for this platform.
No, I mean, why do we need an i2c controller on the virt
board at all ?
> >Forgot to mention, but my prefered approach for providing
> >an i2c controller on the virt board would be to have a
> >PCI i2c controller: that way users who do need it can plug it
> >in with a -device command line option, and users who don't
> >need it never have to worry about it.
> > (We seem to have an ICH9-SMB PCI device already; I have no idea if it's suitable.)
> I didn't find that device suitable because it is part of the Intel
> Southbridge, which may have some Intel platform quirks, and
> we don't need all the things in that IO hub.
That's a pity. Is there a different PCI I2C controller we could model ?
thanks
-- PMM
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