Re: [PATCH] arm64: dts: qcom: monaco-evk: Add off timing constraints for vreg_l8a

[Kamal Wadhwa]

On Wed, Oct 07, 2026 at 11:36:00AM +0200, Manivannan Sadhasivam wrote:
> On Thu, Oct 01, 2026 at 06:37:53PM +0530, Jishnu Prakash wrote:
> > UFS on the Monaco EVK can fail to initialize after probe deferral when
> > vreg_l8a is re-enabled before the supply has fully stabilized. This is
> > caused by the increased discharge and recharge time introduced by
> > additional board-level capacitance in the shared power supply design.
> > 
> > Add the hardware-required off-on-delay and enable-ramp-delay for
> > vreg_l8a to ensure proper power sequencing and reliable UFS
> > initialization across re-probe scenarios.
> > 
> > Additionally, set qcom,regulator-off-debounce-delay-us so that quick
> > disable/enable bounces across probe-defer retries don't power-cycle
> > the rail in hardware at all, rather than needing to wait out the full
> > off-on delay on every retry.
> > 
> 
> This last sentence gives me the impression that we only need
> 'qcom,regulator-off-debounce-delay-us' and not the other two delays.

We will need the other two as well, for the case where the reprobe happens just
after the debounce time has expired and regulator framework has applied OFF,
and now if the request for ON comes even before 10ms, it will be applied
immediately.

eg - UFS driver requested regulator off at t=0ms, the OFF request will not be
applied till t=15ms, however, if the re-probe happens at t=16ms, there will be
only 1ms between the application of the OFF (t=15ms) and ON (t=16ms). So we
need all the 3 properties, the `qcom,regulator-off-debounce-delay-us` just
ensures that we avoid frequent off/on.

Regards,
Kamal

> 
> - Mani
> 
> -- 
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