RE: [PATCH v5 1/4] dt-bindings: usb: add documentation for typec switch simple driver

[Jun Li <jun.li@nxp.com>]

> -----Original Message-----
> From: Rob Herring <robh@kernel.org>
> Sent: Friday, November 6, 2020 6:26 AM
> To: Jun Li <jun.li@nxp.com>
> Cc: heikki.krogerus@linux.intel.com; rafael@kernel.org;
> gregkh@linuxfoundation.org; andriy.shevchenko@linux.intel.com;
> hdegoede@redhat.com; lee.jones@linaro.org;
> mika.westerberg@linux.intel.com; dmitry.torokhov@gmail.com;
> prabhakar.mahadev-lad.rj@bp.renesas.com;
> laurent.pinchart+renesas@ideasonboard.com; linux-usb@vger.kernel.org;
> devicetree@vger.kernel.org; dl-linux-imx <linux-imx@nxp.com>; Peter Chen
> <peter.chen@nxp.com>
> Subject: Re: [PATCH v5 1/4] dt-bindings: usb: add documentation for typec
> switch simple driver
> 
> On Tue, Nov 03, 2020 at 07:40:07PM +0800, Li Jun wrote:
> > Some platforms need a simple driver to do some controls according to
> > typec orientation, this can be extended to be a generic driver with
> > compatible with "typec-orientation-switch".
> >
> > Signed-off-by: Li Jun <jun.li@nxp.com>
> > ---
> > No changes for v5.
> >
> > changes on v4:
> > - Use compatible instead of bool property for switch matching.
> > - Change switch GPIO to be switch simple.
> > - Change the active channel selection GPIO to be optional.
> >
> > previous discussion:
> >
> https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fpatch
> >
> work.ozlabs.org%2Fpatch%2F1054342%2F&amp;data=04%7C01%7Cjun.li%40nxp.c
> >
> om%7C78ca5205695149e2743208d881d9c753%7C686ea1d3bc2b4c6fa92cd99c5c3016
> >
> 35%7C0%7C0%7C637402119664101856%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLj
> >
> AwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=
> > 8TY%2BPRIui6HhxhYE1%2BLmwWL38Vp7SY1Ceb5rGG%2B4DUo%3D&amp;reserved=0
> >
> >  .../bindings/usb/typec-switch-simple.yaml          | 69
> ++++++++++++++++++++++
> >  1 file changed, 69 insertions(+)
> >
> > diff --git
> > a/Documentation/devicetree/bindings/usb/typec-switch-simple.yaml
> > b/Documentation/devicetree/bindings/usb/typec-switch-simple.yaml
> > new file mode 100644
> > index 0000000..244162d
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/usb/typec-switch-simple.yaml
> > @@ -0,0 +1,69 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) %YAML 1.2
> > +---
> > +$id:
> >
> +https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevi
> >
> +cetree.org%2Fschemas%2Fusb%2Ftypec-switch-simple.yaml%23&amp;data=04%
> >
> +7C01%7Cjun.li%40nxp.com%7C78ca5205695149e2743208d881d9c753%7C686ea1d3
> >
> +bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637402119664111854%7CUnknown%7CTWF
> >
> +pbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6
> >
> +Mn0%3D%7C1000&amp;sdata=HjWfKlDLyqb%2FKLlL6vdnyPe%2BnB8pSllhokIXQ%2Bw
> > +yyw8%3D&amp;reserved=0
> > +$schema:
> >
> +https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevi
> >
> +cetree.org%2Fmeta-schemas%2Fcore.yaml%23&amp;data=04%7C01%7Cjun.li%40
> >
> +nxp.com%7C78ca5205695149e2743208d881d9c753%7C686ea1d3bc2b4c6fa92cd99c
> >
> +5c301635%7C0%7C0%7C637402119664111854%7CUnknown%7CTWFpbGZsb3d8eyJWIjo
> >
> +iMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&am
> >
> +p;sdata=z0bO47QVl5gw0UE%2Bx3a5E27ALgz568zp%2Bf4suGlch%2Fo%3D&amp;rese
> > +rved=0
> > +
> > +title: Typec Orientation Switch Simple Solution Bindings
> > +
> > +maintainers:
> > +  - Li Jun <jun.li@nxp.com>
> > +
> > +description: |-
> > +  USB SuperSpeed (SS) lanes routing to which side of typec connector
> > +is
> > +  decided by orientation, this maybe achieved by some simple control
> > +like
> > +  GPIO toggle.
> > +
> > +properties:
> > +  compatible:
> > +    const: typec-orientation-switch
> > +
> > +  switch-gpios:
> > +    description: |
> > +      gpio specifier to switch the super speed active channel,
> > +      GPIO_ACTIVE_HIGH: GPIO state high for cc1;
> > +      GPIO_ACTIVE_LOW:  GPIO state low for cc1.
> 
> What does active mean? There isn't really an active and inactive state, right?
> It's more a mux selecting 0 or 1 input?

Yes, I will change the description:
gpio specifier to select the target channel of mux.

> 
> I think you want flags 0 (aka GPIO_ACTIVE_HIGH) unless there's an inverter
> in the middle.

This depends on the switch IC design and board design, leave 2 flags
(GPIO_ACTIVE_HIGH and GPIO_ACTIVE_LOW) can cover all possible cases.

NXP has 2 diff IC parts for this:
1. PTN36043(used on iMX8MQ)
Output selection control
When SEL=0, RX_AP_*/TX_AP_* are connected to RX_CON_2*/TX_CON_2*, and
RX_CON_1*/TX_CON_1* are connected to VDD thru low ohmic resistor.
When SEL=1, RX_AP_*/TX_AP_* are connected to RX_CON_1*/TX_CON_1*, and
RX_CON_2*/TX_CON_2* are connected to VDD thru low ohmic resistor.

Board design connects RX_CON_1*/TX_CON_1* to typec connector CC1,
so GPIO_ACTIVE_HIGH

2. CBTU02043(used on iMX8MP)
SEL        Function
--------------------------------------
Low        A to B ports and vice versa
High       A to C ports and vice versa

Board design connects B to typec connector CC1, so GPIO_ACTIVE_LOW

Therefore, we need 2 flags.

> 
> > +    maxItems: 1
> > +
> > +  port:
> > +    type: object
> > +    additionalProperties: false
> > +    description: -|
> > +      Connection to the remote endpoint using OF graph bindings that model
> SS
> > +      data bus to typec connector.
> > +
> > +    properties:
> > +      endpoint:
> > +        type: object
> > +        additionalProperties: false
> > +
> > +        properties:
> > +          remote-endpoint: true
> > +
> > +        required:
> > +          - remote-endpoint
> > +
> > +    required:
> > +      - endpoint
> > +
> > +required:
> > +  - compatible
> > +  - port
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    #include <dt-bindings/gpio/gpio.h>
> > +    ptn36043 {
> > +        compatible = "typec-orientation-switch";
> > +        pinctrl-names = "default";
> > +        pinctrl-0 = <&pinctrl_ss_sel>;
> > +        switch-gpios = <&gpio3 15 GPIO_ACTIVE_HIGH>;
> > +
> > +        port {
> > +                usb3_data_ss: endpoint {
> > +                        remote-endpoint = <&typec_con_ss>;
> 
> The data goes from the connector to here and then where? You need a connection
> to the USB host controller.

The orientation switch only need interact with type-c, no any interaction
with USB controller, do we still need a connection to it?

Thanks
Li Jun
> 
> > +                };
> > +        };
> > +    };
> > --
> > 2.7.4
> >