linux-kernel - Re: [PATCH v9 05/15] dt-bindings: connector: Add property to set initial current cap for FRS

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Date:   Tue, 6 Oct 2020 13:29:40 -0500
From:   Rob Herring <robh@...nel.org>
To:     Badhri Jagan Sridharan <badhri@...gle.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Lee Jones <lee.jones@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Thierry Reding <treding@...dia.com>,
        Prashant Malani <pmalani@...omium.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org
Subject: Re: [PATCH v9 05/15] dt-bindings: connector: Add property to set
 initial current cap for FRS

On Mon, Sep 28, 2020 at 07:39:54PM -0700, Badhri Jagan Sridharan wrote:
> This change adds frs-typec-current which allows setting the initial current
> capability of the new source when vSafe5V is applied during PD3.0
> sink Fast Role Swap.

Shouldn't you Cc the person you copied this from?


> Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
> ---
> Changes since v1:
> - Changing patch version to v6 to fix version number confusion.
> 
> Changes since v6:
> - Removed the redundant usb-connector.txt that I created by mistake.
> - Moved to yaml.
> 
> Changes since v7:
> - Rebase 
> 
> Changes since v8:
> - Redefine new-source-frs-typec-current as string enums to address
>   Rob Herring's comment.
> ---
>  .../bindings/connector/usb-connector.yaml     | 26 +++++++++++++++++++
>  include/dt-bindings/usb/pd.h                  | 10 +++++++
>  2 files changed, 36 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/connector/usb-connector.yaml b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> index 9bd52e63c935..0b8cd08a8678 100644
> --- a/Documentation/devicetree/bindings/connector/usb-connector.yaml
> +++ b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> @@ -142,6 +142,32 @@ properties:
>      required:
>        - port@0
>  
> +  new-source-frs-typec-current:
> +    description: Initial current capability of the new source when vSafe5V
> +      is applied during PD3.0 Fast Role Swap. "Table 6-14 Fixed Supply PDO - Sink"
> +      of "USB Power Delivery Specification Revision 3.0, Version 1.2" provides the
> +      different power levels and "6.4.1.3.1.6 Fast Role Swap USB Type-C Current"
> +      provides a detailed description of the field. The sink PDO from current source
> +      reflects the current source's(i.e. transmitter of the FRS signal) power
> +      requirement during fr swap. The current sink (i.e. receiver of the FRS signal),
> +      a.k.a new source, should check if it will be able to satisfy the current source's,
> +      new sink's, requirement during frswap before enabling the frs signal reception.
> +      This property refers to maximum current capability that the current sink can
> +      satisfy. During FRS, VBUS voltage is at 5V, as the partners are in implicit
> +      contract, hence, the power level is only a function of the current capability.
> +      "not-supported" implies sink to source fast role swap not supported.
> +      "default" refers to default USB power level as described by
> +      "Table 6-14 Fixed Supply PDO - Sink".
> +      "1.5A" refers to 1.5A@5V.
> +      "3.0A" refers to 3.0A@5V.


> +
> +    $ref: /schemas/types.yaml#/definitions/string
> +    enum:
> +      - not-supported
> +      - default
> +      - 1.5A
> +      - 3.0A

What happens if the property is not present?

I'm not crazy about mixing strings and what could be a number.

> +
>  required:
>    - compatible
>  
> diff --git a/include/dt-bindings/usb/pd.h b/include/dt-bindings/usb/pd.h
> index 985f2bbd4d24..db1ad4532197 100644
> --- a/include/dt-bindings/usb/pd.h
> +++ b/include/dt-bindings/usb/pd.h
> @@ -35,6 +35,16 @@
>  
>  #define VSAFE5V 5000 /* mv units */
>  
> +/*
> + * Based on "Table 6-14 Fixed Supply PDO - Sink" of "USB Power Delivery Specification Revision 3.0,
> + * Version 1.2"
> + * Initial current capability of the new source when vSafe5V is applied.
> + */
> +#define FRS_NOT_SUPPORTED	0
> +#define FRS_DEFAULT_POWER	1
> +#define FRS_5V_1P5A		2
> +#define FRS_5V_3A		3

Why are these in a DT header, but not used by the binding? Though 
perhaps they should be. Are these numbers from the spec or made up?

> +
>  #define PDO_BATT_MAX_VOLT_SHIFT	20	/* 50mV units */
>  #define PDO_BATT_MIN_VOLT_SHIFT	10	/* 50mV units */
>  #define PDO_BATT_MAX_PWR_SHIFT	0	/* 250mW units */
> -- 
> 2.28.0.709.gb0816b6eb0-goog
>