linux-kernel - Re: [PATCH 03/11] dt-bindings: usb: Add binding for Cypress cypd4226 I2C driver

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Date:   Fri, 28 Oct 2022 13:42:36 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     Wayne Chang <waynec@...dia.com>, gregkh@...uxfoundation.org,
        treding@...dia.com, heikki.krogerus@...ux.intel.com,
        ajayg@...dia.com, kishon@...com, vkoul@...nel.org,
        p.zabel@...gutronix.de, balbi@...nel.org, mathias.nyman@...el.com,
        jckuo@...dia.com, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        singhanc@...dia.com, linux-i2c@...r.kernel.org,
        linux-phy@...ts.infradead.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH 03/11] dt-bindings: usb: Add binding for Cypress cypd4226
 I2C driver


On 28/10/2022 13:31, Thierry Reding wrote:
> On Wed, Oct 26, 2022 at 08:13:57AM +0100, Jon Hunter wrote:
>>
>> On 24/10/2022 08:41, Wayne Chang wrote:
>>> add device-tree binding documentation for Cypress cypd4226 type-C
>>> controller's I2C interface. It is a standard i2c slave with GPIO
>>> input as IRQ interface.
>>>
>>> Signed-off-by: Wayne Chang <waynec@...dia.com>
>>> ---
>>>    .../bindings/usb/cypress,cypd4226.yaml        | 86 +++++++++++++++++++
>>>    1 file changed, 86 insertions(+)
>>>    create mode 100644 Documentation/devicetree/bindings/usb/cypress,cypd4226.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/usb/cypress,cypd4226.yaml b/Documentation/devicetree/bindings/usb/cypress,cypd4226.yaml
>>> new file mode 100644
>>> index 000000000000..5ac28ab4e7a1
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/usb/cypress,cypd4226.yaml
>>> @@ -0,0 +1,86 @@
>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/usb/cypress,cypd4226.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: Cypress cypd4226 UCSI I2C Type-C Controller
>>> +
>>> +maintainers:
>>> +  - Wayne Chang <waynec@...dia.com>
>>> +
>>> +description: |
>>> +  The Cypress cypd4226 UCSI I2C type-C controller is a I2C interface type-C
>>> +  controller.
>>> +
>>> +properties:
>>> +  compatible:
>>> +    const: cypress,cypd4226
>>> +
>>> +  '#address-cells':
>>> +    const: 1
>>> +
>>> +  '#size-cells':
>>> +    const: 0
>>> +
>>> +  reg:
>>> +    const: 0x08
>>> +
>>> +  interrupts:
>>> +    maxItems: 1
>>> +
>>> +  cypress,firmware-build:
>>> +    enum:
>>> +      - nv
>>> +      - gn
>>> +    description: |
>>> +      the name of the CCGx firmware built for product series.
>>> +      should be set one of following:
>>> +      - "nv" for the RTX product series
>>
>> Please add 'NVIDIA' so that it is 'for the NVIDIA RTX product series'
>>
>>> +      - "gn" for the Jetson product series
>>
>> Same here please add 'NVIDIA' so that it is 'for the NVIDIA Jetson product
>> series'.
>>
>> Rob, any concerns about this property in general? Unfortunately, ACPI choose
>> a 16-bit type for this and used 'nv' for the RTX product. I don't find 'gn'
>> for Jetson very descriptive but we need a way to differentiate from RTX.
>>
>> This is needed in the Cypress CCGX driver for the following ...
>>
>> https://lore.kernel.org/lkml/20220928150840.3804313-1-waynec@nvidia.com/
>>
>> Ideally, this should have been included in this series but was sent before.
>> We can always re-work/update the above patch even though it has been queued
>> up now.
> 
> The driver seems to use this 16-bit value only to compare with a
> corresponding field in the firmware headers. How exactly we obtain this
> value is therefore not important. However, since this 16-bit value is
> embedded in firmware images, we also cannot substitute them with
> something more sensible.

I am actually wondering if this is actually embedded in any images 
because I see it populated by the i2c-nvidia-gpu.c driver [0]. So I am 
wondering if we can use PROPERTY_ENTRY_STRING() for this driver instead 
and have a more descriptive name such as 'nvidia,rtx'?

Jon

[0] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/i2c/busses/i2c-nvidia-gpu.c#n261
-- 
nvpublic