linux-kernel - Re: [PATCH v3 3/7] dt-bindings: ufs: common: add OPP table

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Message-ID: <20220513183220.GE1922@thinkpad>
Date:   Sat, 14 May 2022 00:02:20 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Taniya Das <tdas@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-scsi@...r.kernel.org,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v3 3/7] dt-bindings: ufs: common: add OPP table

On Fri, May 13, 2022 at 11:10:20PM +0530, Manivannan Sadhasivam wrote:
> On Fri, May 13, 2022 at 08:13:43AM +0200, Krzysztof Kozlowski wrote:
> > Except scaling UFS and bus clocks, it's necessary to scale also the
> > voltages of regulators or power domain performance state levels.  Adding
> > Operating Performance Points table allows to adjust power domain
> > performance state, depending on the UFS clock speed.
> > 
> > OPPv2 deprecates previous property limited to clock scaling:
> > freq-table-hz.
> > 
> > Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> > Reviewed-by: Rob Herring <robh@...nel.org>
> > 
> > ---
> > 
> > Cc: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  .../devicetree/bindings/ufs/ufs-common.yaml   | 34 +++++++++++++++++--
> >  1 file changed, 31 insertions(+), 3 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/ufs/ufs-common.yaml b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
> > index 47a4e9e1a775..d7d2c8a136bb 100644
> > --- a/Documentation/devicetree/bindings/ufs/ufs-common.yaml
> > +++ b/Documentation/devicetree/bindings/ufs/ufs-common.yaml
> > @@ -20,11 +20,24 @@ properties:
> >        items:
> >          - description: Minimum frequency for given clock in Hz
> >          - description: Maximum frequency for given clock in Hz
> > +    deprecated: true
> >      description: |
> > +      Preferred is operating-points-v2.
> > +
> >        Array of <min max> operating frequencies in Hz stored in the same order
> > -      as the clocks property. If this property is not defined or a value in the
> > -      array is "0" then it is assumed that the frequency is set by the parent
> > -      clock or a fixed rate clock source.
> > +      as the clocks property. If either this property or operating-points-v2 is
> > +      not defined or a value in the array is "0" then it is assumed that the
> > +      frequency is set by the parent clock or a fixed rate clock source.
> > +
> > +  operating-points-v2:
> > +    description:
> > +      Preferred over freq-table-hz.
> > +      If present, each OPP must contain array of frequencies stored in the same
> > +      order for each clock.  If clock frequency in the array is "0" then it is
> > +      assumed that the frequency is set by the parent clock or a fixed rate
> > +      clock source.
> 
> This description mentions only the clocks and not voltages. But in theory, the
> OPP table can contain other parameters like current, bandwidth, etc,... So to
> avoid confusion, I'd suggest to get rid of the description.
> 
> > +
> > +  opp-table: true
> >  
> >    interrupts:
> >      maxItems: 1
> > @@ -75,8 +88,23 @@ properties:
> >  
> >  dependencies:
> >    freq-table-hz: [ 'clocks' ]
> > +  operating-points-v2: [ 'clocks', 'clock-names' ]
> 
> What about voltage regulators if relevant opp property is present?
> 

Current UFS driver model won't allow us to change both voltage supplies and clks
using OPP implementation. So please ignore my above comment.

Thanks,
Mani

> Thanks,
> Mani
> 
> >  
> >  required:
> >    - interrupts
> >  
> > +allOf:
> > +  - if:
> > +      required:
> > +        - freq-table-hz
> > +    then:
> > +      properties:
> > +        operating-points-v2: false
> > +  - if:
> > +      required:
> > +        - operating-points-v2
> > +    then:
> > +      properties:
> > +        freq-table-hz: false
> > +
> >  additionalProperties: true
> > -- 
> > 2.32.0
> > 
> 
> -- 
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