Re: [PATCH] arm64: dts: qcom: qcm6490-fairphone-fp5: Enable UFS

[Konrad Dybcio]

On 10/2/23 09:02, Luca Weiss wrote:
> On Fri Sep 29, 2023 at 3:12 PM CEST, Konrad Dybcio wrote:
> > On 29.09.2023 11:52, Luca Weiss wrote:
> > > Enable the UFS phy and controller so that we can access the internal
> > > storage of the phone.
> > >
> > > At the same time we need to bump the minimum voltage used for UFS VCC,
> > > otherwise it doesn't initialize properly. The new range is taken from
> > > the vcc-voltage-level property downstream.
> > >
> > > See also the following link for more information about the VCCQ/VCCQ2:
> > > https://gerrit-public.fairphone.software/plugins/gitiles/kernel/msm-extra/devicetree/+/1590a3739e7dc29d2597307881553236d492f188/fp5/yupik-idp-pm7250b.dtsi#207
> > >
> > > Signed-off-by: Luca Weiss <luca.weiss@xxxxxxxxxxxxx>
> > > ---
> > > I'm not 100% convinced about the regulator range change. For sure with
> > > the original voltage range the UFS fails to initialize, but looking at
> > > downstream kernel during runtime (debugfs) we see the VCC voltage
> > > switches between 2.4V (idle?) and 2.952V (active?). But even with this
> > > change in mainline the regulator would always stay at 2.504V which is
> > > for sure lower than the downstream operating voltage of 2.952V. Behavior
> > > wise I don't see a difference between ~2.5V and ~2.9V.
> > >
> > > Should I just constrain the regulator here to min=max=2.952V? Or just
> > > say it's okay as-is?
> > >
> > > Depends on: https://lore.kernel.org/linux-arm-msm/20230927081858.15961-1-quic_nitirawa@xxxxxxxxxxx/
> > > ---
> > There's a little funny hack inside the driver
> >
> > #if defined(CONFIG_SCSI_UFSHCD_QTI)
> >                          if (vreg->low_voltage_sup && !vreg->low_voltage_active && on)
> >                                  min_uV = vreg->max_uV;
> > #endif
> >
> > so, when the ufs is in use, it's pinned to vmax
>
> Hi Konrad,
>
> Are you implying I *should* or *should not* pin the voltage range to
> 2.952V-2.952V for mainline?
Neither, voltage scaling should be implemented :P

But for now, pinning it to 2.952 const is the right temporary
solution, as having working UFS is generally better than one
that can only idle in a stable manner :D

Konrad