On 2020-09-15 06:43, Bjorn Andersson wrote:
On Tue 15 Sep 03:14 CDT 2020, nguyenb@xxxxxxxxxxxxxx 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@xxxxxxxxxxxxxx>
> > Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
> > Signed-off-by: Bao D. Nguyen <nguyenb@xxxxxxxxxxxxxx>
> > ---
> > 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
Thank you all for your comments. The current driver hardcoding 2.7V Vcc
min voltage
does not work for UFS3.0+ devices according to the UFS device JEDEC
spec. However, we will
try to address it in a different way.
Regards,
Bao
>
> 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
> >
