Re: [PATCH 0/2] Adds designware i2c module and adds it to virt arm

[Chris Rauer]

Hi Phil,

> What about using virtio-gpio & bitbang I2C?
>
> - virtio-gpio
> https://lore.kernel.org/qemu-devel/20201127182917.2387-5-info@metux.net/
>
> - bitbang I2C already in: hw/i2c/bitbang_i2c.c

Sorry for the delay.

That looks like it might be doable with a bit more work creating the ACPI entries for the bitbang I2C.  This definitely seems more appropriate on the ARM_VIRT platform instead of putting a specific controller in.

For my uses, I will have to stick with the designware controller since it matches the system I'm emulating a little more closely.  We can hold back the designware stuff until another SoC platform is interested in using this controller (since it seems like it is a common one).  Hopefully someone will find another use for the controller patches someday.

Thanks again for looking at our patches.

-Chris

On Wed, Jan 26, 2022 at 3:42 PM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:

+Enrico Weigelt

On 26/1/22 19:03, Peter Maydell wrote:
> 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 ?

What about using virtio-gpio & bitbang I2C?

- virtio-gpio
https://lore.kernel.org/qemu-devel/20201127182917.2387-5-info@metux.net/

- bitbang I2C already in: hw/i2c/bitbang_i2c.c

Regards,

Phil.