linux-kernel - Re: [PATCH] dt-bindings: spi: xilinx: Add clocks & clock-names properties

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Message-ID: <1195de0e-4a14-446f-bd1f-0116d4abf18b@kernel.org>
Date: Thu, 3 Oct 2024 09:01:29 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: "Mahapatra, Amit Kumar" <amit.kumar-mahapatra@....com>,
 Conor Dooley <conor@...nel.org>
Cc: "broonie@...nel.org" <broonie@...nel.org>,
 "robh@...nel.org" <robh@...nel.org>, "krzk+dt@...nel.org"
 <krzk+dt@...nel.org>, "conor+dt@...nel.org" <conor+dt@...nel.org>,
 "Simek, Michal" <michal.simek@....com>,
 "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
 "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "git (AMD-Xilinx)" <git@....com>,
 "amitrkcian2002@...il.com" <amitrkcian2002@...il.com>
Subject: Re: [PATCH] dt-bindings: spi: xilinx: Add clocks & clock-names
 properties

On 03/10/2024 08:23, Mahapatra, Amit Kumar wrote:
> Hello Conor,
> 
>> -----Original Message-----
>> From: Conor Dooley <conor@...nel.org>
>> Sent: Monday, September 30, 2024 10:10 PM
>> To: Mahapatra, Amit Kumar <amit.kumar-mahapatra@....com>
>> Cc: Krzysztof Kozlowski <krzk@...nel.org>; broonie@...nel.org; robh@...nel.org;
>> krzk+dt@...nel.org; conor+dt@...nel.org; Simek, Michal
>> <michal.simek@....com>; linux-spi@...r.kernel.org; devicetree@...r.kernel.org;
>> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; git (AMD-Xilinx)
>> <git@....com>; amitrkcian2002@...il.com
>> Subject: Re: [PATCH] dt-bindings: spi: xilinx: Add clocks & clock-names properties
>>
>> On Mon, Sep 30, 2024 at 03:44:47PM +0000, Mahapatra, Amit Kumar wrote:
>>> Hello Conor,
>>>
>>>>>>>>> Subject: Re: [PATCH] dt-bindings: spi: xilinx: Add clocks &
>>>>>>>>> clock-names properties
>>>>>>>>>
>>>>>>>>> On Mon, Sep 23, 2024 at 06:02:42PM +0530, Amit Kumar Mahapatra
>> wrote:
>>>>>>>>>> Include the 'clocks' and 'clock-names' properties in the AXI
>>>>>>>>>> Quad-SPI bindings. When the AXI4-Lite interface is enabled,
>>>>>>>>>> the core operates in legacy mode, maintaining backward
>>>>>>>>>> compatibility with version 1.00, and uses 's_axi_aclk' and
>>>>>>>>>> 'ext_spi_clk'. For the AXI interface, it uses 's_axi4_aclk' and
>> 'ext_spi_clk'.
>>>>
>>>>>>>>>> +      properties:
>>>>>>>>>> +        clock-names:
>>>>>>>>>> +          items:
>>>>>>>>>> +            - const: s_axi_aclk
>>>>>>>>>> +            - const: ext_spi_clk
>>>>>>>>>
>>>>>>>>> These are all clocks, there should be no need to have "clk" in the names.
>>>>>>>>
>>>>>>>> These are the names exported by the IP and used by the DTG.
>>>>>>>
>>>>>>> So? This is a binding, not a verilog file.
>>>>>>
>>>>>> Axi Quad SPI is an FPGA-based IP, and the clock names are
>>>>>> derived from the IP signal names as specified in the IP documentation [1].
>>>>>> We chose these names to ensure alignment with the I/O signal
>>>>>> names listed in Table 2-2 on page 19 of [1].
>>>>>>
>>>>>> [1]
>>>>>> chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://www.amd.
>>>>>> com/content/dam/xilinx/support/documents/ip_documentation/axi_qu
>>>>>> ad_s
>>>>>> pi/v3_2/pg153-axi-quad-spi.pdf
>>>>>
>>>>> So if hardware engineers call them "pink_pony_clk_aclk_really_clk"
>>>>> we should follow...
>>>>>
>>>>>  - bus or axi
>>>>>  - ext_spi or spi
>>>>>
>>>>> You have descriptions of each item to reference real signals.
>>>>> Conor's comment is valid - do no make it verilog file.
>>>>>
>>>>>>
>>>>>>>
>>>>>>>>>> +
>>>>>>>>>> +    else:
>>>>>>>>>> +      properties:
>>>>>>>>>> +        clock-names:
>>>>>>>>>> +          items:
>>>>>>>>>> +            - const: s_axi4_aclk
>>>>>>>>>> +            - const: ext_spi_clk
>>>>>
>>>>> Nah, these are the same.
>>>>
>>>> They may be different, depending on whether or not the driver has to
>>>> handle "axi4- lite" versus "axi" differently. That said, I find the
>>>> commit message kinda odd in that it states that axi4-lite goes with the s_axi_aclk
>> clock and axi goes with s_axi4_aclk.
>>>
>>> Apologies for the typo. When the AXI4 interface is enabled, it uses
>>> s_axi4_aclk, and when the AXI4-Lite interface is enabled, it uses s_axi_aclk.
>>>
>>> In my next series I will update my commit message & change the
>>> clock-names 's_axi4_aclk', 's_axi_aclk' & 'ext_spi_clk' to 'axi4',
>>> 'axi' & 'ref' respectively
>>
>> There's no driver here, so it is hard to know (why isn't there?) - are you using the axi
> 
> We are working on the driver. Once it is ready we will send it to upstream.

Why would you send separate binding from driver? That's only making
everything more difficult...

> 
>> v axi4 to do some sort of differentiation in the driver?
> In the driver we don't do any different operations based on the clocks , 
> we simply enable the available clocks in the driver.

So it is the same clock?

Best regards,
Krzysztof