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

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Message-ID: <ae520641-38a4-405e-89d0-e0921dfc7cff@linaro.org>
Date: Mon, 16 Sep 2024 18:05:04 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Amit Sunil Dhamne <amitsd@...gle.com>, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 heikki.krogerus@...ux.intel.com, gregkh@...uxfoundation.org
Cc: 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 11/09/2024 02:07, 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>

Please work on mainline, not ancient tree. You cannot get my CC address
like that from mainline. It's not possible. So either you don't develop
on mainline or you don't use get_maintainers.pl/b4/patman.


> ---
>  .../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

timer of what? OS behavior?

> +      "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

Do not describe what DT is. We all know what DT properties allow.
Instead describe how this relates to hardware or boards.

All this is wrongly wrapped. See Coding style (and I am not telling you
the value on purpose, so you will read the coding style) .

> +      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.

And what is the default?

> +    $ref: /schemas/types.yaml#/definitions/uint32-array

I guess you want matrix here.

> +
>  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>;

Incorporate it into existing example.

> +        };
> +    };
> 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) */

Please expand this a bit, so we won't have to reach to external sources.

> +#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


Best regards,
Krzysztof