Re: [PATCH 1/1] Force ELAN06FA touchpad I2C bus freq to 100KHz

R Ha
2025-01-11T16:05:34Z

Hi,

I updated the description, please let me know if it's covered everything.

Just as a question, because the touchpad works well at both 100KHz and
1000KHz, is it better to force it to 100KHz or 1000KHz? I was
considering that the Microsoft docs [1] specified that the frequency
should be "no less than 400KHz", but didn't change it for now because
the touchpad feels the same at 100KHz and 1000KHz, including for
gestures.

Is it possible that there will be any sort of compatibility issues if
the speed is set to 1000KHz? From what I can tell, the only other
device on I2C1 is the "Intel Smart Sound" related device, but I'm not
exactly sure what that does or whether it will work at 1000KHz. The
sound output itself seems to be unaffected regardless of the
frequency, though I don't think the other device is directly related
to sound output.

[1]: https://learn.microsoft.com/en-us/windows-hardware/design/component-guidelines/touchpad-device-bus-connectivity#acpi-table-entries

On Fri, Jan 10, 2025 at 6:07 AM Mika Westerberg
<mika.westerberg@linux.intel.com> wrote:
>
> On Fri, Jan 10, 2025 at 01:45:03PM +0200, Jarkko Nikula wrote:
> > On 1/10/25 1:26 PM, Mika Westerberg wrote:
> > > Hi,
> > >
> > > On Fri, Jan 10, 2025 at 02:31:26AM -0600, R Ha wrote:
> > > > Hi,
> > > >
> > > > Sounds like a good idea. I'm a little worried I'm missing something,
> > > > so I think being able to check my earlier answers will help as well.
> > > > I'm sending the entire output as attachments, but let me know if it's
> > > > better to upload them somewhere and paste the link instead. Some of
> > > > the ssdt* files are missing, but they're empty files so Gmail won't
> > > > let me attach them.
> > >
> > > Thanks for sharing! Okay checked now dsdt.dsl (the other files are not
> > > relevant here) and what I can tell the device is supposed to be run at 400
> > > kHz. I suspect this is what Windows is doing as well, there is nothing that
> > > indicates otherwise.
> > >
> > > And since this is a standard I2C HID device it should just work (as it does
> > > not require any vendor specific driver even in Windows).
> > >
> > > Only thing I can think of that affects this is the LCNT/HCNT and SDA hold
> > > values of the I2C designware controller (and maybe the input clock) but
> > > there is nothing in the ACPI tables that set these so it could be that the
> > > Windows driver uses different values for those and that explains why it
> > > works better there.
> > >
> > > @Jarkko, do you have any input here? If we cannot figure a better way then
> > > I don't see other option than to add this quirk.
> >
> > Unfortunately I don't have idea.
>
> Okay thanks anyway! Then I don't see any other option than adding that
> quirk.
>
> @R Ha, can you then submit a new version of the patch with the latest
> details in the changelog?