Re: [PATCH 3/4] arm64: dts: qcom: qcm6490-fairphone-fp5: Enable CCI pull-up

Bryan O'Donoghue
2025-10-02T13:12:19Z

On 02/10/2025 13:45, Konrad Dybcio wrote:
> On 10/2/25 12:15 PM, Griffin Kroah-Hartman wrote:
>> Enable vreg_l6p which is used as a pull-up for the CCI busses, to make
>> sure I2C communication works as expected.

"vreg_l6p is the voltage source for the pull-up resistor"

>>
>> Signed-off-by: Griffin Kroah-Hartman<griffin.kroah@fairphone.com>
>> ---
> Makes me wonder if we should maybe extend the CCI definition
> (or maybe the common i2c-bus binding?) to accept an external
> pull-up supply, as this is a common problem.. (+Bryan, Wolfram)

always-on is up to the platform - i.e. do you care about the
floating-state of the i2c bus in power-collapse anyway ? Feels like
something up to the platform designers.
> We could then shut down the regulator when cameras are not
> in use, preserving some trace amounts of power.> Or maybe L6P is already used as a pull-up supply for more things
> onboard and should be always-on either way? Could you please
> check that, Griffin?

If we drop always-on and introduce a "pullup-supply" to the CCI bindings
then, it would be up the CCI driver to enable/disable the bus pullups
and then we can optionally do the power-rail disable when entering
power-collapse.

That'd be nice.

As-is though I personally am fine with the patch as-is with the updated
commit text above - consider the CCI change as extra homework ;)

Assuming the commit log is tweaked.

Reviewed-by: Bryan O'Donoghue <bod@kernel.org>