From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: nguyenb@codeaurora.org
Cc: cang@codeaurora.org, asutoshd@codeaurora.org,
martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
linux-arm-msm@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
Avri Altman <Avri.Altman@wdc.com>, Vinod Koul <vkoul@kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS
Date: Tue, 15 Sep 2020 08:43:35 -0500 [thread overview]
Message-ID: <20200915134335.GE670377@yoga> (raw)
In-Reply-To: <748d238a3d9e53834a498c6f37f9f3c9@codeaurora.org>
On Tue 15 Sep 03:14 CDT 2020, nguyenb@codeaurora.org wrote:
> On 2020-09-14 21:41, Bjorn Andersson wrote:
> > On Tue 01 Sep 01:00 CDT 2020, Bao D. Nguyen wrote:
> >
> > > UFS's specifications supports a range of Vcc operating
> > > voltage levels. Add documentation for the UFS's Vcc voltage
> > > levels setting.
> > >
> > > Signed-off-by: Can Guo <cang@codeaurora.org>
> > > Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
> > > Signed-off-by: Bao D. Nguyen <nguyenb@codeaurora.org>
> > > ---
> > > Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > index 415ccdd..7257b32 100644
> > > --- a/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > +++ b/Documentation/devicetree/bindings/ufs/ufshcd-pltfrm.txt
> > > @@ -23,6 +23,8 @@ Optional properties:
> > > with "phys" attribute, provides phandle
> > > to UFS PHY node
> > > - vdd-hba-supply : phandle to UFS host controller supply
> > > regulator node
> > > - vcc-supply : phandle to VCC supply regulator node
> > > +- vcc-voltage-level : specifies voltage levels for VCC supply.
> > > + Should be specified in pairs (min, max),
> > > units uV.
> >
> > What exactly are these pairs representing?
> The pair is the min and max Vcc voltage request to the PMIC chip.
> As a result, the regulator output voltage would only be in this range.
>
If you have static min/max voltage constraints for a device on a
particular board the right way to handle this is to adjust the board's
regulator-min-microvolt and regulator-max-microvolt accordingly - and
not call regulator_set_voltage() from the river at all.
In other words, you shouldn't add this new property to describe
something already described in the node vcc-supply points to.
Regards,
Bjorn
> >
> > Is this supposed to be 3 pairs of (min,max) for vcc, vcc and vccq2 to be
> > passed into a regulator_set_voltage() for each regulator?
> Yes, that's right. I should include the other power supplies in this change
> as well.
> >
> > Or are these some sort of "operating points" for the vcc-supply?
> >
> > Regards,
> > Bjorn
> >
> > > - vccq-supply : phandle to VCCQ supply regulator node
> > > - vccq2-supply : phandle to VCCQ2 supply regulator node
> > > - vcc-supply-1p8 : For embedded UFS devices, valid VCC range
> > > is 1.7-1.95V
> > > --
> > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> > > Forum,
> > > a Linux Foundation Collaborative Project
> > >
next prev parent reply other threads:[~2020-09-16 0:31 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 6:00 [PATCH v1 0/2] Supports Reading UFS's Vcc Voltage Levels from DT Bao D. Nguyen
2020-09-01 6:00 ` [PATCH v1 1/2] scsi: dt-bindings: ufs: Add vcc-voltage-level for UFS Bao D. Nguyen
2020-09-13 9:35 ` Avri Altman
2020-09-14 16:19 ` nguyenb
2020-09-14 18:35 ` Rob Herring
2020-09-15 8:10 ` nguyenb
2020-09-18 19:01 ` Rob Herring
2020-09-22 0:22 ` nguyenb
2020-09-22 0:36 ` Bjorn Andersson
2020-09-23 17:32 ` nguyenb
2020-09-15 4:41 ` Bjorn Andersson
2020-09-15 8:14 ` nguyenb
2020-09-15 13:43 ` Bjorn Andersson [this message]
2020-09-15 16:47 ` nguyenb
2020-09-15 18:36 ` Bjorn Andersson
2020-09-01 6:00 ` [PATCH v1 2/2] scsi: ufs: Support reading UFS's Vcc voltage from device tree Bao D. Nguyen
2020-09-13 9:37 ` Avri Altman
2020-09-14 18:43 ` nguyenb
2020-09-15 6:51 ` Avri Altman
2020-09-15 13:46 ` Bjorn Andersson
2020-09-10 1:29 ` [PATCH v1 0/2] Supports Reading UFS's Vcc Voltage Levels from DT nguyenb
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