Re: [RFC 1/3] dt-bindings: usb: qcom,dwc3: Add support for multiple power-domains

[Sriram Dash]

On 3/6/2024 1:03 PM, Krishna Kurapati PSSNV wrote:
> On 3/6/2024 12:33 PM, Krzysztof Kozlowski wrote:
> > On 05/03/2024 19:03, Sriram Dash wrote:
> > > On 3/5/2024 10:37 PM, Krzysztof Kozlowski wrote:
> > > > On 05/03/2024 17:57, Sriram Dash wrote:
> > > > > Some target systems allow multiple resources to be managed by 
> > > > > firmware.
> > > > > On these targets, tasks related to clocks, regulators, resets, and
> > > > > interconnects can be delegated to the firmware, while the remaining
> > > > > responsibilities are handled by Linux.
> > > > >
> > > > > To support the management of partial resources in Linux and leave 
> > > > > the rest
> > > > > to firmware, multiple power domains are introduced. Each power 
> > > > > domain can
> > > > > manage one or more resources, depending on the specific use case.
> > > > >
> > > > > These power domains handle SCMI calls to the firmware, enabling the
> > > > > activation and deactivation of firmware-managed resources.
> > > > >
> > > > > Signed-off-by: Sriram Dash <quic_sriramd@xxxxxxxxxxx>
> > > > > ---
> > > > >    .../phy/qcom,sc8280xp-qmp-usb3-uni-phy.yaml        | 74 
> > > > > ++++++++++++++++------
> > > > >    .../bindings/phy/qcom,usb-snps-femto-v2.yaml       | 49 
> > > > > ++++++++++++--
> > > > >    .../devicetree/bindings/usb/qcom,dwc3.yaml         | 37 ++++++++++-
> > > > >    3 files changed, 130 insertions(+), 30 deletions(-)
> > > > >
> > > > > diff --git 
> > > > > a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb3-uni-phy.yaml b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb3-uni-phy.yaml
> > > > > index 1e2d4dd..53b9ba9 100644
> > > > > --- 
> > > > > a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb3-uni-phy.yaml
> > > > > +++ 
> > > > > b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-usb3-uni-phy.yaml
> > > > > @@ -44,7 +44,32 @@ properties:
> > > > >        maxItems: 5
> > > > >      power-domains:
> > > > > -    maxItems: 1
> > > > > +    description: specifies a phandle to PM domain provider node
> > > >
> > > > Please drop all redundant descriptions. Adding them is not even related
> > > > to this patch.
> > >
> > > Thanks Krzysztof for the super quick response !
> > > Sure. will drop the description for power-domain
> > > and power-doamin-names.
> > >
> > > > > +    minItems: 1
> > > > > +    maxItems: 2
> > > > > +
> > > > > +  power-domain-names:
> > > > > +    description:
> > > > > +      A list of power domain name strings sorted in the same order 
> > > > > as the
> > > > > +      power-domains property.
> > > > > +
> > > > > +      For platforms where some resource are firmware managed, the 
> > > > > name
> > > > > +      corresponding to the index of an SCMI domain provider can be
> > > > > +      "usb_core" or "usb_transfer".
> > > > > +    items:
> > > > > +      - const: usb_core
> > > > > +      - const: usb_transfer
> > > >
> > > > How is this related to fw-managed? I fail to see it. Don't mix
> > > > independent problems in one patch.
> > >
> > > Some of the the resources like clocks, regulators, etc will be
> > > controlled by the firmware instead of OS. However, some resources
> > > still will be controlled by OS (interrupts for example).
> > >
> > > So, to support the management of partial resources in Linux, and
> > > offload the other resource management to firmware, multiple power
> > > domains are introduced. They will be corresponding to different
> > > hw blocks.
> > >
> > > Do you suggest splitting the addition of power-domain-names and
> > > addition of fw-managed property in separate patches for bindings!
> > >
> > > > > +
> > > > > +  qmp,fw-managed:
> > > >
> > > > Please do not upstream vendor code directly, but perform basic
> > > > adjustment to upstream Linux kernel. There is no such company as gmp.
> > > >
> > > > Run this first through your internal review process.
> > >
> > > This property is newly introduced for the qmp superspeed phy and
> > > similar dt properties are introduced for hsphy and dwc3 qcom
> > > controller glue layer driver. It will govern the suspend/ resume
> > > of the resources (by firmware or OS) as required.
> >
> > So that's your answer to "there is no such company as gmp"? It's not
> > relevant at all.
> >
> > Please run it through internal review first.
> Hi Sriram,
>
>   QMP indicates the driver name "QMP Phy" (for super speed mode of 
> operation), not the company name. If this property is for identification 
> of fw management to be done / (or not to be done) in QMP Phy, then 
> please rename is appropriately. Check how other properties are defined 
> in the QMP bindings and add "qcom" at beginning preferably. For 
> reference as to how properties were added to femto phy driver: [1].
>
> [1]: 
> https://patchwork.kernel.org/project/linux-arm-msm/patch/1662480933-12326-2-git-send-email-quic_kriskura@xxxxxxxxxxx/

Thanks for the references Krzysztof/Krishna.
I got suggestion from Dmitry on the use of the
property too. Indeed we will be the scmi based
clock/ PD management on SA8775. So, we will
introduce a new compatible string and take the
decision in driver accordingly.


> Regards,
> Krishna,