Re: [PATCH v7 1/6] DONOTMERGE: arm64: dts: ti: Add TI TPS65219 PMIC support for AM642 SK board.

[jerome Neanne]

On 16/12/2022 07:21, Vignesh Raghavendra wrote:
> On 16/12/22 03:11, Nishanth Menon wrote:
> > On 18:22-20221215, Mark Brown wrote:
> > > On Thu, Dec 15, 2022 at 11:54:11AM -0600, Nishanth Menon wrote:
> > > > On 16:09-20221215, Mark Brown wrote:
> > >
> > > > > That proposal looks really non-idiomatic and quite unusual, if there's a
> > > > > fixed voltage supply to the LDO I'd expect to see it modeled as a fixed
> > > > > voltage regulator.  I'm not sure what the use of bypass here is trying
> > > > > to accomplish TBH.
> > >
> > > > The problem is this - the default NVM in the PMIC is setup such that
> > > > VSET value =3.3v and bypass bit set (makes sense since the vin=3.3v).
> > >
> > > This implies no voltage drop over the LDO?  Sounds a bit suspect.
> >
> > Not the choice I'd probably have made ;)
> >
> > > > Now the constraint is bypass bit cannot be changed without the LDO
> > > > being switched off.
>
> Per https://www.ti.com/lit/ds/symlink/tps65219.pdf (7.3.6 Linear
> Regulators).
>
> LDOs have two modes:
>
> 1. Load switch mode: in this case, output voltages of 1.5V up to 5.5V
> are supported.
>
> 2 Linear regulator LDO mode where output voltage is programmable in the
> range of 0.6V to 3.4V in 50mV-steps with possibility of bypass.
>
> (CAUTION on page 25):
> A mode change between LDO(/bypass) and LSW-mode must only be performed,
> when this regulator is disabled!
> A change between LDO and bypass-mode (supported by LDO1 and LDO2 only)
> is supported during operation.
>
> So, seems like bypass can be toggled even with LDO on?
> I possibly miss-interpreted this caution statement which leads to that 
situation.

Your understanding sounds correct. My mistake... Sorry for that


Regards,
Jerome.