| Message ID | 20230929064852.16642-1-piyush.mehta@amd.com |
|---|---|
| Headers | show |
| Series | usb: phy: Add platform driver support for ULPI phys | expand |
> -----Original Message----- > From: Mehta, Piyush > Sent: Wednesday, October 4, 2023 5:15 PM > To: Rob Herring <robh@kernel.org> > Cc: gregkh@linuxfoundation.org; Simek, Michal <michal.simek@amd.com>; > krzysztof.kozlowski+dt@linaro.org; conor+dt@kernel.org; > peter.chen@kernel.org; linus.walleij@linaro.org; paul@crapouillou.net; > arnd@arndb.de; linux-usb@vger.kernel.org; devicetree@vger.kernel.org; > linux-kernel@vger.kernel.org; git (AMD-Xilinx) <git@amd.com> > Subject: RE: [RFC PATCH 1/3] dt-binding: usb: ulpi-phy: add ulpi-phy binding > > Hi All, > > > -----Original Message----- > > From: Rob Herring <robh@kernel.org> > > Sent: Monday, October 2, 2023 10:30 PM > > To: Mehta, Piyush <piyush.mehta@amd.com> > > Cc: gregkh@linuxfoundation.org; Simek, Michal <michal.simek@amd.com>; > > krzysztof.kozlowski+dt@linaro.org; conor+dt@kernel.org; > > peter.chen@kernel.org; linus.walleij@linaro.org; paul@crapouillou.net; > > arnd@arndb.de; linux-usb@vger.kernel.org; devicetree@vger.kernel.org; > > linux- kernel@vger.kernel.org; git (AMD-Xilinx) <git@amd.com> > > Subject: Re: [RFC PATCH 1/3] dt-binding: usb: ulpi-phy: add ulpi-phy > > binding > > > > On Fri, Sep 29, 2023 at 12:18:50PM +0530, Piyush Mehta wrote: > > > Create an ulpi-phy binding to read and write PHY registers with > > > explicit control of the address and data using the usb.VIEWPORT register. > > > > > > Signed-off-by: Piyush Mehta <piyush.mehta@amd.com> > > > --- > > > This binding patch was created to support generic platforms. This > > > binding will be modified in accordance with patch [3/3] procedures. > > > One of the approch may be Create a zynq phy platform driver in > > > "driver/usb/phy" with driver source "phy-ulpi-zynq-usb.c" and then > > > the binding will be particular to the Xilinx/AMD zynq platform. > > > > > > This binding was built with the Zynq hardware design example in > > > consideration of as a generic platform. The viewport provide access > > > the Chipidea controller to interface with the ULPI PHY. > > > --- > > > .../devicetree/bindings/usb/ulpi-phy.yaml | 48 +++++++++++++++++++ > > > 1 file changed, 48 insertions(+) > > > create mode 100644 > > > Documentation/devicetree/bindings/usb/ulpi-phy.yaml > > > > > > diff --git a/Documentation/devicetree/bindings/usb/ulpi-phy.yaml > > > b/Documentation/devicetree/bindings/usb/ulpi-phy.yaml > > > new file mode 100644 > > > index 000000000000..490b2f610129 > > > --- /dev/null > > > +++ b/Documentation/devicetree/bindings/usb/ulpi-phy.yaml > > > @@ -0,0 +1,48 @@ > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) %YAML 1.2 > > > +--- > > > +$id: http://devicetree.org/schemas/usb/ulpi-phy.yaml# > > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > > + > > > +title: ULPI PHY- Generic platform > > > + > > > +maintainers: > > > + - Piyush Mehta <piyush.mehta@amd.com> > > > + > > > +properties: > > > + compatible: > > > + const: ulpi-phy > > > + > > > + reg: > > > + maxItems: 1 > > > + > > > + '#phy-cells': > > > + const: 0 > > > + > > > + external-drv-vbus: > > > + description: > > > + If present, configure ulpi-phy external supply to drive 5V on VBus. > > > + type: boolean > > > + > > > + view-port: > > > + $ref: /schemas/types.yaml#/definitions/uint32 > > > + description: > > > + Address to read and write PHY registers with explicit control of > > > + the address and data using the usb.VIEWPORT register. > > > + > > > +required: > > > + - compatible > > > + - reg > > > + - view-port > > > + > > > +additionalProperties: false > > > + > > > +examples: > > > + - | > > > + phy0@e0002000 { > > > + compatible = "ulpi-phy"; > > > + #phy-cells = <0x00>; > > > + reg = <0xe0002000 0x1000>; > > > + view-port = <0x170>; > > > > I don't understand. Do you have an MMIO address and the VIEWPORT > > address to the PHY? You need both? > > Yes, we need both. > > The ULPI Link wrapper passes-through packet data and interprets Rx > commands as well as send Tx commands and provide viewport services to the > software. The ULPI link wrapper interfaces between the port controller (a bus > similar to UTMI+ that connects to the rest of the controller and its registers) > and the ULPI interface. > > Name XUSBPS_ULPIVIEW_OFFSET > Address 0x00000170 > > Description ULPI Viewport > > The register provides indirect access to the ULPI PHY register set. Although the > core performs access to the ULPI PHY register set, there may be extraordinary > circumstances where software may need direct access. > > ULPI PHY Viewport > The ULPI viewport provides a mechanism for software to read and write PHY > registers with explicit control of the address and data using the usb.VIEWPORT > register. An interrupt is generated when a transaction is complete, including > when the requested read data is available. > > > > > There's already a defined binding for ULPI bus: > > > > Documentation/devicetree/bindings/usb/ulpi.txt > > > > Why can't you use/expand that? > > > > Rob > > We need your input to determine the best approach . We did preliminary > research and discovered few possibilities: > > USB Node { > ............. > ULPI PHY Node { // child node > ................. > compatible = "ulpi-phy-"; > #phy-cells = <0x00>; > .............. > }; > }; > > https://github.com/torvalds/linux/blob/master/Documentation/devicetree/b > indings/phy/qcom%2Cusb-hs-phy.yaml#L100 > https://github.com/torvalds/linux/blob/master/Documentation/devicetree/b > indings/usb/ci-hdrc-usb2.yaml#L338 > https://github.com/torvalds/linux/blob/master/drivers/usb/chipidea/ci_hdrc > _msm.c#L245 > https://github.com/torvalds/linux/blob/master/drivers/phy/qualcomm/phy- > qcom-usb-hs.c#L85 > [This implementation is based on ulpi driver: > https://github.com/torvalds/linux/blob/master/drivers/phy/qualcomm/phy- > qcom-usb-hs.c#L287C1-L287C19] > > OR > > https://github.com/torvalds/linux/blob/master/drivers/usb/chipidea/ci_hdrc > _imx.c#L81 > https://github.com/torvalds/linux/blob/master/drivers/usb/chipidea/ci_hdrc > _imx.c#L176 > https://github.com/torvalds/linux/blob/master/drivers/usb/chipidea/usbmis > c_imx.c#L234 > https://github.com/torvalds/linux/blob/master/drivers/usb/phy/phy-mxs- > usb.c#L191 > [This implementation is based on platform driver: > https://github.com/torvalds/linux/blob/master/drivers/usb/phy/phy-mxs- > usb.c#L848] > > Note: > Above examples are to show the interface between the Chipidea Controller > and PHY. > > Are these possibilities aligning with your inputs? > Please share your inputs on the above alternate design approaches. > Regards, > Piyush Mehta BR, PM