linux-kernel - Re: [RFC 1/2] dt-bindings: connector: Add property to set pd timer values

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Message-ID: <5iakowhmqc3hbstmwbs6ixabr27hf2dfz2m4do4qvsrtgrdn72@r7xqawwgebla>
Date: Thu, 12 Sep 2024 13:05:35 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Amit Sunil Dhamne <amitsd@...gle.com>
Cc: robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org, 
	conor+dt@...nel.org, heikki.krogerus@...ux.intel.com, gregkh@...uxfoundation.org, 
	linux-kernel@...r.kernel.org, kyletso@...gle.com, rdbabiera@...gle.com, 
	Badhri Jagan Sridharan <badhri@...gle.com>, linux-usb@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [RFC 1/2] dt-bindings: connector: Add property to set pd timer
 values

On Tue, Sep 10, 2024 at 05:07:05PM GMT, Amit Sunil Dhamne wrote:
> This commit adds a new property "pd-timers" to enable setting of
> platform/board specific pd timer values for timers that have a range of
> acceptable values.
> 
> Cc: Badhri Jagan Sridharan <badhri@...gle.com>
> Cc: linux-usb@...r.kernel.org
> Cc: devicetree@...r.kernel.org
> Signed-off-by: Amit Sunil Dhamne <amitsd@...gle.com>
> ---
>  .../bindings/connector/usb-connector.yaml     | 23 +++++++++++++++++++
>  include/dt-bindings/usb/pd.h                  |  8 +++++++
>  2 files changed, 31 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/connector/usb-connector.yaml b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> index fb216ce68bb3..9be4ed12f13c 100644
> --- a/Documentation/devicetree/bindings/connector/usb-connector.yaml
> +++ b/Documentation/devicetree/bindings/connector/usb-connector.yaml
> @@ -253,6 +253,16 @@ properties:
>  
>      additionalProperties: false
>  
> +  pd-timers:
> +    description: An array of u32 integers, where an even index (i) is the timer (referenced in
> +      dt-bindings/usb/pd.h) and the odd index (i+1) is the timer value in ms (refer
> +      "Table 6-68 Time Values" of "USB Power Delivery Specification Revision 3.0, Version 1.2 " for
> +      the appropriate value). For certain timers the PD spec defines a range rather than a fixed
> +      value. The timers may need to be tuned based on the platform. This dt property allows the user
> +      to assign specific values based on the platform. If these values are not explicitly defined,
> +      TCPM will use a valid default value for such timers.
> +    $ref: /schemas/types.yaml#/definitions/uint32-array

Is it really necessary to use the array property? I think it's easier
and more logical to define corresponding individual properties, one per
the timer.

> +
>  dependencies:
>    sink-vdos-v1: [ sink-vdos ]
>    sink-vdos: [ sink-vdos-v1 ]
> @@ -478,3 +488,16 @@ examples:
>              };
>          };
>      };
> +
> +  # USB-C connector with PD timers
> +  - |
> +    #include <dt-bindings/usb/pd.h>
> +    usb {
> +        connector {
> +            compatible = "usb-c-connector";
> +            label = "USB-C";
> +            pd-timers =
> +                <PD_TIMER_SINK_WAIT_CAP 600>,
> +                <PD_TIMER_CC_DEBOUNCE 170>;
> +        };
> +    };
> diff --git a/include/dt-bindings/usb/pd.h b/include/dt-bindings/usb/pd.h
> index e6526b138174..6c58c30f3f39 100644
> --- a/include/dt-bindings/usb/pd.h
> +++ b/include/dt-bindings/usb/pd.h
> @@ -465,4 +465,12 @@
>  	 | ((vbm) & 0x3) << 15 | (curr) << 14 | ((vbi) & 0x3f) << 7	\
>  	 | ((gi) & 0x3f) << 1 | (ct))
>  
> +/* PD Timer definitions */
> +/* tTypeCSinkWaitCap (Table 6-68 Time Values, USB PD3.1 Spec) */
> +#define PD_TIMER_SINK_WAIT_CAP		0
> +/* tPSSourceOff (Table 6-68 Time Values, USB PD3.1 Spec) */
> +#define PD_TIMER_PS_SOURCE_OFF		1
> +/* tCCDebounce (Table 4-33 CC Timing, USB Type-C Cable & Connector Spec Rel2.2) */
> +#define PD_TIMER_CC_DEBOUNCE		2
> +
>  #endif /* __DT_POWER_DELIVERY_H */
> -- 
> 2.46.0.598.g6f2099f65c-goog
> 

-- 
With best wishes
Dmitry