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

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 17/09/2024 03:59, Amit Sunil Dhamne wrote:
> Hi Krzysztof,
> 
> Thanks for the review!
> 
> On 9/16/24 9:05 AM, Krzysztof Kozlowski wrote:
>> 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@google.com>
>>> Cc: linux-usb@vger.kernel.org
>>> Cc: devicetree@vger.kernel.org
>>> Signed-off-by: Amit Sunil Dhamne <amitsd@google.com>
>> Please work on mainline, not ancient tree. You cannot get my CC address
>> like that from mainline.
> I was working off gregkh's tree on usb-next branch as that's suggested 
> for USB development.
> 
> 
>> It's not possible. So either you don't develop
>> on mainline or you don't use get_maintainers.pl/b4/patman.
>>
> The above branch and even the tree on Linus' master branch has you
> listed as a maintainer
> (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/MAINTAINERS#n17181).
> I guess that's why the get_maintainers script probably returned your
> email id when I ran it. Please let me know if I missed something :).

You really just skimmed over my email... I know how maintainers work.

So I REPEAT: You cannot get this email address you Cced. Point me to the
line in your tree having such email. The one here:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/MAINTAINERS#n17181

does not have it.

> 
> 
>>> ---
>>>   .../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?
> In the context of USB Type C Power Delivery (PD), timers are run on the 
> typec protocol driver
> (usb/typec/tcpm/tcpm.c).
> These are used to keep track of min/max or range of time required to 
> enter a PD state with the
> goal of a successful USB typec capabilities negotiation.  Eg., the timer 
> PD_TIMER_SINK_WAIT_CAP (referred to as SinkWaitCapTimer in spec)would be 
> responsible to keep track of whether a power source sent us (as sink) PD 
> source capabilities pkts within 600ms (say), if yes, then we would 
> transition to the next state or do a state machine reset. USB PD 3.1 
> spec refers to these elements as timers and therefore referred to as 
> such here.
> 
> 
>>> +      "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) .
> 
> 
> Ack. Thanks for pointing it out, I will fix both the above in the next 
> revision.
> 
> 
>>
>>> +      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?
> 
> Defaults are given in (include/linux/usb/pd.h). But I guess I should 
> have probably mentioned
> that here.
> 
> 
>>
>>> +    $ref: /schemas/types.yaml#/definitions/uint32-array
>> I guess you want matrix here.
> 
> Yes, I should have. Though, I will be re-implementing this such that 
> each timer is represented
> as a separate property based on Rob and Dmitry's suggestion in
> https://lore.kernel.org/lkml/20240916163328.GA394032-robh@kernel.org/ .
> 
>>> +
>>>   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.
>>
> Ack.
> 
> 
>>> +        };
>>> +    };
>>> 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.
> 
> Ack.
> 
> I will incorporate all of your review comments.
> 
> Since you are no longer maintaining the
> "OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" component, please let 

Who said that? You CC wrong emails because either you work on ancient
tree or you do not use tools like get_maintainers.pl or b4. You cannot
get this email from proper process. It is not physically possible
because that email is nowhere mentioned.

> me know
> if you'd still like to be CC'ed in the subsequent revisions.


Damn, just use standard tools. You are not supposed to invent maintainers.

<form letter>
Please use scripts/get_maintainers.pl to get a list of necessary people
and lists to CC (and consider --no-git-fallback argument). It might
happen, that command when run on an older kernel, gives you outdated
entries. Therefore please be sure you base your patches on recent Linux
kernel.

Tools like b4 or scripts/get_maintainer.pl provide you proper list of
people, so fix your workflow. Tools might also fail if you work on some
ancient tree (don't, instead use mainline) or work on fork of kernel
(don't, instead use mainline). Just use b4 and everything should be
fine, although remember about `b4 prep --auto-to-cc` if you added new
patches to the patchset.
</form letter>

Best regards,
Krzysztof