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Date:   Wed, 6 Apr 2022 18:40:45 -0700
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Subject: Re: [PATCH v5 04/11] dt-bindings: Add HTE bindings
Content-Language: en-US
To:     Rob Herring <robh@kernel.org>
Cc:     thierry.reding@gmail.com, jonathanh@nvidia.com,
        smangipudi@nvidia.com, linux-kernel@vger.kernel.org,
        linux-tegra@vger.kernel.org, linux-gpio@vger.kernel.org,
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        warthog618@gmail.com, devicetree@vger.kernel.org,
        linux-doc@vger.kernel.org
References: <20220329054521.14420-1-dipenp@nvidia.com>
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From:   Dipen Patel <dipenp@nvidia.com>
In-Reply-To: <YkRtzJjHQvmYNlK8@robh.at.kernel.org>
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On 3/30/22 7:48 AM, Rob Herring wrote:
> On Tue, Mar 29, 2022 at 05:19:10PM -0700, Dipen Patel wrote:
>> Hi,
>>
>> On 3/29/22 4:25 PM, Rob Herring wrote:
>>> On Mon, Mar 28, 2022 at 10:45:14PM -0700, Dipen Patel wrote:
>>>> Introduces HTE devicetree binding details for the HTE subsystem. It
>>>> includes examples for the consumers, binding details for the providers
>>>> and specific binding details for the Tegra194 based HTE providers.
>>>>
>>>> Signed-off-by: Dipen Patel <dipenp@nvidia.com>
>>>> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
>>>> ---
>>>> Changes in v2:
>>>> - Replace hte with hardware-timestamp for property names
>>>> - Renamed file
>>>> - Removed example from the common dt binding file.
>>>>
>>>> Changes in v3:
>>>> - Addressed grammatical errors.
>>>> - Removed double plural from the respective properties.
>>>> - Added dual license.
>>>> - Prefixed "nvidia" in nvidia specific properties.
>>>>
>>>> Changes in v4:
>>>> - Corrected make dt_binding_check error.
>>>>
>>>> Changes in v5:
>>>> - Addressed review comments.
>>>>
>>>>  .../hte/hardware-timestamps-common.yaml       | 29 +++++++
>>>>  .../devicetree/bindings/hte/hte-consumer.yaml | 43 ++++++++++
>>>>  .../bindings/hte/nvidia,tegra194-hte.yaml     | 82 +++++++++++++++++++
>>>>  3 files changed, 154 insertions(+)
>>>>  create mode 100644 Documentation/devicetree/bindings/hte/hardware-timestamps-common.yaml
>>>>  create mode 100644 Documentation/devicetree/bindings/hte/hte-consumer.yaml
>>>>  create mode 100644 Documentation/devicetree/bindings/hte/nvidia,tegra194-hte.yaml
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/hte/hardware-timestamps-common.yaml b/Documentation/devicetree/bindings/hte/hardware-timestamps-common.yaml
>>>> new file mode 100644
>>>> index 000000000000..e8a69ceccd56
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/hte/hardware-timestamps-common.yaml
>>>> @@ -0,0 +1,29 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevicetree.org%2Fschemas%2Fhte%2Fhardware-timestamps-common.yaml%23&amp;data=04%7C01%7Cdipenp%40nvidia.com%7C0e094f6ae7b642c970f308da125c64d4%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637842485301457320%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=4UcTV375zNF44HeIpQcDV%2Bp3VJXdtjomZYGWWsUJf%2FA%3D&amp;reserved=0
>>>> +$schema: https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevicetree.org%2Fmeta-schemas%2Fcore.yaml%23&amp;data=04%7C01%7Cdipenp%40nvidia.com%7C0e094f6ae7b642c970f308da125c64d4%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637842485301457320%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=fGoLuKpVFMNOsh%2BbJ6dLhpky63Y6zQ1oNkiOHDQ%2Bud0%3D&amp;reserved=0
>>>> +
>>>> +title: Hardware timestamp providers
>>>> +
>>>> +maintainers:
>>>> +  - Dipen Patel <dipenp@nvidia.com>
>>>> +
>>>> +description:
>>>> +  Some devices/SoCs have hardware time stamping engines which can use hardware
>>>> +  means to timestamp entity in realtime. The entity could be anything from
>>>> +  GPIOs, IRQs, Bus and so on. The hardware timestamp engine (HTE) present
>>>> +  itself as a provider with the bindings described in this document.
>>>> +
>>>> +properties:
>>>> +  $nodename:
>>>> +    pattern: "^hardware-timestamp(@.*|-[0-9a-f])?$"
>>>> +
>>>> +  "#hardware-timestamp-cells":
>>>> +    description:
>>>> +      Number of cells in a HTE specifier.
>>>> +
>>>> +required:
>>>> +  - "#hardware-timestamp-cells"
>>>> +
>>>> +additionalProperties: true
>>>> diff --git a/Documentation/devicetree/bindings/hte/hte-consumer.yaml b/Documentation/devicetree/bindings/hte/hte-consumer.yaml
>>>> new file mode 100644
>>>> index 000000000000..be69f63aa8c3
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/hte/hte-consumer.yaml
>>>> @@ -0,0 +1,43 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevicetree.org%2Fschemas%2Fhte%2Fhte-consumer.yaml%23&amp;data=04%7C01%7Cdipenp%40nvidia.com%7C0e094f6ae7b642c970f308da125c64d4%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637842485301457320%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=E3fspCvDDE5%2F6opK%2FdtpaY5%2FscsPURvDV7O7%2B%2FdbtEQ%3D&amp;reserved=0
>>>> +$schema: https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fdevicetree.org%2Fmeta-schemas%2Fcore.yaml%23&amp;data=04%7C01%7Cdipenp%40nvidia.com%7C0e094f6ae7b642c970f308da125c64d4%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637842485301457320%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=fGoLuKpVFMNOsh%2BbJ6dLhpky63Y6zQ1oNkiOHDQ%2Bud0%3D&amp;reserved=0
>>>> +
>>>> +title: HTE Consumer Device Tree Bindings
>>>> +
>>>> +maintainers:
>>>> +  - Dipen Patel <dipenp@nvidia.com>
>>>> +
>>>> +select: true
>>>> +
>>>> +description:
>>>> +  HTE properties should be named "hardware-timestamps". The exact meaning of
>>>> +  each hardware-timestamps property must be documented in the device tree
>>> The meaning of the cells needs to be documented. You are documenting the 
>>> meaning of 'hardware-timestamps' here.
>> This is for the consumer side, meaning of the cells will be documented in the provider
>>
>> binding document.
> Right cells are opaque to the consumer. What bothered me is 
> hardware-timestamps already has an 'exact meaning'. You need to me more 
> exact as to what should be documented. We don't want what 
> 'hardware-timestamps' is described again. What needs to be documented is 
> how many entries, what each entry is (for the consumer), and the order.
>
>
>>>> +  binding for each device. An optional property "hardware-timestamp-names" may
>>>> +  contain a list of strings to label each of the HTE devices listed in the
>>>> +  "hardware-timestamps" property.
>>>> +
>>>> +properties:
>>>> +  hardware-timestamps:
>>> I'm wondering if we should just drop 'hardware'. What other kind of 
>>> timestamps are we going to have in DT? software-timestamps? No.
>> I believe this makes it explicit and leaves no room for second guess. If
>>
>> only timestamps, ambiguity then will be which timestamp it is i.e. through hardware
>>
>> engine, pps, ptp and so on...
> Those aren't hardware timestamps, too? If those needed a similar 
> binding, couldn't they use this binding? PTP at least is sometimes an 
> separate, external chip IIRC.

I am fine with this idea of dropping "hardware" prefix, will update the patch.

I believe this will be applicable to all other properties for example hardware-timestamp-cell

as well, right?

>
> Rob