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

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Message-ID: <cac1b912-e08b-4643-b081-834fdee30ea7@linaro.org>
Date:   Fri, 29 Sep 2023 15:12:39 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Luca Weiss <luca.weiss@...rphone.com>,
        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 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

Konrad