Re: [PATCH] i2c: qcom-geni: restore tSCL with 32MHz I2C fast-mode

[Daniel J Blueman]

On Wed, 30 Sept 2026 at 15:19, Mukesh Savaliya
<mukesh.savaliya@xxxxxxxxxxxxxxxx> wrote:
>
> Thanks Daniel !
>
> On 9/29/2026 9:44 AM, Daniel J Blueman wrote:
> > Commit cb97bf3d4f91 ("i2c: qcom-geni: Fix hardcoded clock index in
> > SE_GENI_CLK_SEL") allowed GENI to use 32MHz clock. This changed I2C
> > timing, making the Yoga Slim 7x keyboard (ITE 048D:8987) unusable
> > on all boots, and touchpad unusable on some boots, resulting in:
> >
> >    i2c_hid_of 1-003a: unexpected HID descriptor bcdVersion (0x0000)
> >    i2c_hid_of 1-002c: failed to fetch HID descriptor: -110
> >
> > With this change, t_high_cnt 3 and clk_div 4 gave a tSCL of 375ns
> > versus the previous default of 521ns, however the I2C spec has a
> > minimum tSCL of 600ns.
> >
> > Restore tSCL to the spec with t_high_cnt 5 giving a 625ns tSCL,
> > verified on Lenovo Yoga Slim 7x X1E-80100.
> >
>
> There might be a final count which i should get and update back.
> Since this fix is working though not suggested per hardware guidance,
> should we consider as temporary fix and move ahead to prevent failing
> usecase ?

If you can get the final values into a patch for the next -rc instead
of my fix here, that would be the minimal path for everyone. You or
the hardware team can cross-check against the I2C standard as I did
[1, p44].

I would revert the original patch if there is hardware that uses the
I2C 1MHz fast-mode, since the current timings aren't to spec, but also
weren't before.

Thanks,
  Dan

-- [1] https://www.nxp.com/docs/en/user-guide/UM10204.pdf
-- 
Daniel J Blueman