Re: [PATCH v4 10/18] dt-bindings: usb: Convert DWC USB3 bindings to DT schema

[Serge Semin]

On Wed, Nov 11, 2020 at 10:34:10AM +0100, Krzysztof Kozlowski wrote:
> On Wed, 11 Nov 2020 at 10:32, Serge Semin
> <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On Wed, Nov 11, 2020 at 10:16:28AM +0100, Krzysztof Kozlowski wrote:
> > > On Wed, Nov 11, 2020 at 12:08:45PM +0300, Serge Semin wrote:
> > > > DWC USB3 DT node is supposed to be compliant with the Generic xHCI
> > > > Controller schema, but with additional vendor-specific properties, the
> > > > controller-specific reference clocks and PHYs. So let's convert the
> > > > currently available legacy text-based DWC USB3 bindings to the DT schema
> > > > and make sure the DWC USB3 nodes are also validated against the
> > > > usb-xhci.yaml schema.
> > > >
> > > > Note we have to discard the nodename restriction of being prefixed with
> > > > "dwc3@" string, since in accordance with the usb-hcd.yaml schema USB nodes
> > > > are supposed to be named as "^usb(@.*)".
> > > >
> > > > Signed-off-by: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
> > > >
> > > > ---
> > > >
> > > > Changelog v2:
> > > > - Discard '|' from the descriptions, since we don't need to preserve
> > > >   the text formatting in any of them.
> > > > - Drop quotes from around the string constants.
> > > > - Fix the "clock-names" prop description to be referring the enumerated
> > > >   clock-names instead of the ones from the Databook.
> > > >
> > > > Changelog v3:
> > > > - Apply usb-xhci.yaml# schema only if the controller is supposed to work
> > > >   as either host or otg.
> > > >
> > > > Changelog v4:
> > > > - Apply usb-drd.yaml schema first. If the controller is configured
> > > >   to work in a gadget mode only, then apply the usb.yaml schema too,
> > > >   otherwise apply the usb-xhci.yaml schema.
> > > > - Discard the Rob'es Reviewed-by tag. Please review the patch one more
> > > >   time.
> > > > ---
> > > >  .../devicetree/bindings/usb/dwc3.txt          | 125 --------
> > > >  .../devicetree/bindings/usb/snps,dwc3.yaml    | 303 ++++++++++++++++++
> > > >  2 files changed, 303 insertions(+), 125 deletions(-)
> > > >  delete mode 100644 Documentation/devicetree/bindings/usb/dwc3.txt
> > > >  create mode 100644 Documentation/devicetree/bindings/usb/snps,dwc3.yaml
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
> > > > deleted file mode 100644
> > > > index d03edf9d3935..000000000000
> > > > --- a/Documentation/devicetree/bindings/usb/dwc3.txt
> > > > +++ /dev/null
> > > > @@ -1,125 +0,0 @@
> > > > -synopsys DWC3 CORE
> > > > -
> > > > -DWC3- USB3 CONTROLLER. Complies to the generic USB binding properties
> > > > -      as described in 'usb/generic.txt'
> > > > -
> > > > -Required properties:
> > > > - - compatible: must be "snps,dwc3"
> > > > - - reg : Address and length of the register set for the device
> > > > - - interrupts: Interrupts used by the dwc3 controller.
> >
> > > > - - clock-names: list of clock names. Ideally should be "ref",
> > > > -                "bus_early", "suspend" but may be less or more.
> > > > - - clocks: list of phandle and clock specifier pairs corresponding to
> > > > -           entries in the clock-names property.
> > > > -
> > > > -Exception for clocks:
> > > > -  clocks are optional if the parent node (i.e. glue-layer) is compatible to
> > > > -  one of the following:
> > > > -    "cavium,octeon-7130-usb-uctl"
> > > > -    "qcom,dwc3"
> > > > -    "samsung,exynos5250-dwusb3"
> > > > -    "samsung,exynos5433-dwusb3"
> > > > -    "samsung,exynos7-dwusb3"
> > > > -    "sprd,sc9860-dwc3"
> > > > -    "st,stih407-dwc3"
> > > > -    "ti,am437x-dwc3"
> > > > -    "ti,dwc3"
> > > > -    "ti,keystone-dwc3"
> > > > -    "rockchip,rk3399-dwc3"
> > > > -    "xlnx,zynqmp-dwc3"
> > >
> > > What happened with this part of dtschema? It sees you removed it.
> >
> > You meant "bindings", right?
> >
> > I don't think it's a good idea to implement that weak binding in the
> > generic DWC USB3 DT schema. Of course I could have created it under
> > the allOf conditional schema and stuff. But in that case we would have
> > needed to support the clock-related vendor-specific peculiarities in
> > both the generic DWC USB3 DT schema and in the vendor-specific binding
> > files. That wouldn't be that maintainable. As I see it all the
> > vendor-specific clock requirements should be reflected in the
> > glue-node DT schema. The DWC USB3 node binding just declares the
> > clocks as optional. Moreover the DWC USB3 driver also considers them
> > as optional.
> 

> Sure, rationale is good, but it needs to be explained in commit msg.
> Otherwise you state that you just "convert" but it's not a simple
> conversion. The meaning is changed.

Right. I should have explained it in the commit log. It has just
slipped out of my mind. If v3 is needed I'll add the proper text in the
commit message.

-Sergey

> 
> 
> Best regards,
> Krzysztof