Re: [PATCH V1 2/4] arm64: dts: qcom: sm8750: add max-microamp for UFS PHY and PLL supplies

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 8/8/25 9:29 AM, Krzysztof Kozlowski wrote:
> On Wed, Aug 06, 2025 at 09:13:38PM +0530, Nitin Rawat wrote:
>> Add `vdda-phy-max-microamp` and `vdda-pll-max-microamp` properties to
>> the UFS PHY node in the device tree.
>>
>> These properties define the maximum current (in microamps) expected
>> from the PHY and PLL regulators. This allows the PHY driver to
>> configure regulator load accurately and ensure proper regulator
>> mode based on load requirements.
> 
> That's not the property of phy, but regulator.
> 
> Also reasoning is here incomplete - you just post downstream code. :/

The reason for this change is good, but perhaps not explained clearly

All of these values refer to the maximum current draw that needs to be
allocated on a shared voltage supply for this peripheral (because the
supply's capabilities change depending on the maximum potential load
at any given time, which the regulator driver must be aware of)

This is a property of a regulator *consumer*, i.e. if we had a chain
of LEDs hanging off of this supply, we'd need to specify NUM_LEDS * 
MAX_CURR under the "led chain" device, to make sure that if the
aggregated current requirements go over a certain threshold (which is
unknown to Linux and hidden in RPMh fw), the regulator can be
reconfigured to allow for a higher current draw (likely at some
downgrade to efficiency)

Konrad