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

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Date:   Mon, 02 Oct 2023 09:02:38 +0200
From:   "Luca Weiss" <luca.weiss@...rphone.com>
To:     "Konrad Dybcio" <konrad.dybcio@...aro.org>,
        "Andy Gross" <agross@...nel.org>,
        "Bjorn Andersson" <andersson@...nel.org>,
        "Rob Herring" <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        "Conor Dooley" <conor+dt@...nel.org>,
        "Nitin Rawat" <quic_nitirawa@...cinc.com>
Cc:     <~postmarketos/upstreaming@...ts.sr.ht>,
        <phone-devel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: qcom: qcm6490-fairphone-fp5: Enable UFS

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@...rphone.com>
> > ---
> > 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@quicinc.com/
> > ---
> 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?

Regards
Luca

>
> Konrad