linux-kernel - Re: [PATCH v4 2/3] dt-bindings: fpga: xlnx,fpga-selectmap: add DT schema

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Date: Mon, 4 Mar 2024 08:30:16 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Charles Perry <charles.perry@...oirfairelinux.com>,
 Rob Herring <robh+dt@...nel.org>, yilun xu <yilun.xu@...el.com>
Cc: mdf <mdf@...nel.org>, Allen VANDIVER <avandiver@...kem-imaje.com>,
 Brian CODY <bcody@...kem-imaje.com>, hao wu <hao.wu@...el.com>,
 Tom Rix <trix@...hat.com>,
 krzysztof kozlowski+dt <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Michal Simek <michal.simek@....com>,
 linux-fpga <linux-fpga@...r.kernel.org>,
 devicetree <devicetree@...r.kernel.org>,
 linux-kernel <linux-kernel@...r.kernel.org>,
 linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 2/3] dt-bindings: fpga: xlnx,fpga-selectmap: add DT
 schema

On 03/03/2024 18:21, Charles Perry wrote:
> On Feb 27, 2024, at 3:10 AM, Krzysztof Kozlowski krzysztof.kozlowski@...aro.org wrote:
> 
>> On 21/02/2024 20:50, Charles Perry wrote:
>>> Document the SelectMAP interface of Xilinx 7 series FPGA.
>>>
>>> Signed-off-by: Charles Perry <charles.perry@...oirfairelinux.com>
>>> ---
>>>  .../bindings/fpga/xlnx,fpga-selectmap.yaml    | 86 +++++++++++++++++++
>>>  1 file changed, 86 insertions(+)
>>>  create mode 100644
>>>  Documentation/devicetree/bindings/fpga/xlnx,fpga-selectmap.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/fpga/xlnx,fpga-selectmap.yaml
>>> b/Documentation/devicetree/bindings/fpga/xlnx,fpga-selectmap.yaml
>>> new file mode 100644
>>> index 0000000000000..08a5e92781657
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/fpga/xlnx,fpga-selectmap.yaml
>>> @@ -0,0 +1,86 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/fpga/xlnx,fpga-selectmap.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: Xilinx SelectMAP FPGA interface
>>> +
>>> +maintainers:
>>> +  - Charles Perry <charles.perry@...oirfairelinux.com>
>>> +
>>> +description: |
>>> +  Xilinx 7 Series FPGAs support a method of loading the bitstream over a
>>> +  parallel port named the SelectMAP interface in the documentation. Only
>>> +  the x8 mode is supported where data is loaded at one byte per rising edge of
>>> +  the clock, with the MSB of each byte presented to the D0 pin.
>>> +
>>> +  Datasheets:
>>> +
>>> https://www.xilinx.com/support/documentation/user_guides/ug470_7Series_Config.pdf
>>> +
>>> +allOf:
>>> +  - $ref: /schemas/memory-controllers/mc-peripheral-props.yaml#
>>> +
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - xlnx,fpga-xc7s-selectmap
>>> +      - xlnx,fpga-xc7a-selectmap
>>> +      - xlnx,fpga-xc7k-selectmap
>>> +      - xlnx,fpga-xc7v-selectmap
>>> +
>>> +  reg:
>>> +    description:
>>> +      At least 1 byte of memory mapped IO
>>> +    maxItems: 1
>>> +
>>> +  prog_b-gpios:
>>
>> I commented on this and still see underscore. Nothing in commit msg
>> explains why this should have underscore. Changelog is also vague -
>> describes that you brought back underscores, instead of explaining why
>> you did it.
>>
>> So the same comments as usual:
>>
>> No underscores in names.
>>
>> Best regards,
>> Krzysztof
> 
> Hello Krzysztof,
> 
> Yes, I've gone full circle on that issue. Here's what I tried so far:

And what part of the commit description allows me to understand this?

> 
>  1) Reuse the same gpio names: Duplicates errors of the past, Krzysztof
>     doesn't like it.
>  2) Different gpio names for new driver only: Makes the driver code
>     overly complicated, Yilun doesn't like it.

That's a new driver, right? So what is complicated here? You have new
code and you take prog-b or prog_b?

>  3) Change gpio names for both drivers, deprecate the old names: Makes
>     the DT binding and the driver code overly complicated, Rob doesn't
>     like it.

I don't think I proposed changing existing bindings.

> 
> I think that while the driver code shouldn't be the driving force for
> the DT spec, it can be a good indication that the spec is unpractical to
> implement.

What is impractical in implementing this? You just pass either A or B to
function requesting GPIO. Just choose proper name.

> 
> In this case, there are two interfaces on a chip that uses the same GPIO
> protocol, it would only make sense that they use the same names, this
> discards solution #2.

I don't understand this. You have devm_gpiod_get() in your new code. Why
is it difficult to use different name?



Best regards,
Krzysztof