linux-kernel - Re: [PATCH 1/3] spi: dt-bindings: add doc for Amlogic A113L2 SFC

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Message-ID: <d8248069-c12e-4f72-a625-c4f68aa42f1f@kernel.org>
Date: Sun, 17 Aug 2025 09:20:54 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Xianwei Zhao <xianwei.zhao@...ogic.com>
Cc: Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Liang Yang <liang.yang@...ogic.com>,
 Feng Chen <feng.chen@...ogic.com>, linux-spi@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-amlogic@...ts.infradead.org
Subject: Re: [PATCH 1/3] spi: dt-bindings: add doc for Amlogic A113L2 SFC

On 14/08/2025 08:38, Xianwei Zhao wrote:
> Hi Krzysztof,
>     Thanks for your reply.
> 
> On 2025/8/14 00:19, Krzysztof Kozlowski wrote:
>> [ EXTERNAL EMAIL ]
>>
>> On 13/08/2025 11:34, Xianwei Zhao wrote:
>>> Hi Krzysztof,
>>>      Thanks  for your reply.
>>>
>>> On 2025/8/13 15:36, Krzysztof Kozlowski wrote:
>>>> [ EXTERNAL EMAIL ]
>>>>
>>>> On 13/08/2025 08:13, Xianwei Zhao wrote:
>>>>>>> +allOf:
>>>>>>> +  - $ref: /schemas/spi/spi-controller.yaml#
>>>>>>> +
>>>>>>> +properties:
>>>>>>> +  compatible:
>>>>>>> +    const: amlogic,a4-spifc
>>>>>>> +
>>>>>>> +  reg:
>>>>>>> +    items:
>>>>>>> +      - description: core registers
>>>>>>> +      - description: parent clk control registers
>>>>>>
>>>>>> Why are you poking to parent node or to clock registers? This looks like
>>>>>> mixing up device address spaces.
>>>>>>
>>>>>
>>>>> The SPIFC bus clock multiplexes EMMC modules, so the corresponding
>>>>> frequency division register is also in EMMC module. The SPIFC and the
>>>>> EMMC modules cannot be used simultaneously.
>>>>
>>>> Then obviously you cannot put here EMMC or parent registers.
>>>>
>>>> It looks really like you miss proper hardware representation.
>>>>
>>>
>>> It does seem a bit unusual. However, in our hardware design, EMMC and
>>> SFC modules are integrated, and they share common resources such as the
>>> clock and I/O pins .They are mutually exclusive.
>>>
>>
>> How did you express it in DT? This looks similar to serial engines and
>> such are not implemented independently.
>>
> 
> The hardware design provides this clock for both modules — EMMC and 
> SPIFC. A control bit (bit 31: Cfg_NAND, where 0 = Port C only, 1 = NAND) 
> is used to determine which module uses the clock.
> 
> It's not that NAND is using EMMC’s resources; rather, the configuration 
> register controlling this selection is located within the EMMC module, 
> which makes the setup appear somewhat unusual.

No, how did you express in DT that they are mutually exclusive?

> 
> In the device tree (DT), I'll just refer directly to the clock frequency 
> division control register.

This does not solve the exclusive usage...


Best regards,
Krzysztof