linux-kernel - Re: [PATCH v6 25/27] ARM: dts: at91: sam9x7: add device tree for SoC

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Message-ID: <a36c4d23-e2fe-4bf5-a262-5eb9828e6e7a@microchip.com>
Date: Wed, 28 Aug 2024 08:25:09 +0000
From: <Varshini.Rajendran@...rochip.com>
To: <krzk@...nel.org>, <robh@...nel.org>, <krzk+dt@...nel.org>,
	<conor+dt@...nel.org>, <Nicolas.Ferre@...rochip.com>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 25/27] ARM: dts: at91: sam9x7: add device tree for SoC

On 27/08/24 6:18 pm, Krzysztof Kozlowski wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On 27/08/2024 11:50, Varshini.Rajendran@...rochip.com wrote:
>> Hi Krzysztof,
>>
>> Apologies for the delay in response.
>>
>> On 31/07/24 2:00 pm, Krzysztof Kozlowski wrote:
>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>
>>> On 29/07/2024 09:09, Varshini Rajendran wrote:
>>>> Add device tree file for SAM9X7 SoC family.
>>>>
>>>> Co-developed-by: Nicolas Ferre <nicolas.ferre@...rochip.com>
>>>> Signed-off-by: Nicolas Ferre <nicolas.ferre@...rochip.com>
>>>> Signed-off-by: Varshini Rajendran <varshini.rajendran@...rochip.com>
>>>
>>> ...
>>>
>>>> +
>>>> +             can1: can@...04000 {
>>>> +                     compatible = "bosch,m_can";
>>>> +                     reg = <0xf8004000 0x100>, <0x300000 0xbc00>;
>>>> +                     reg-names = "m_can", "message_ram";
>>>> +                     interrupts = <30 IRQ_TYPE_LEVEL_HIGH 0>,
>>>> +                                  <69 IRQ_TYPE_LEVEL_HIGH 0>;
>>>> +                     interrupt-names = "int0", "int1";
>>>> +                     clocks = <&pmc PMC_TYPE_PERIPHERAL 30>, <&pmc PMC_TYPE_GCK 30>;
>>>> +                     clock-names = "hclk", "cclk";
>>>> +                     assigned-clocks = <&pmc PMC_TYPE_CORE PMC_UTMI>, <&pmc PMC_TYPE_GCK 30>;
>>>> +                     assigned-clock-rates = <480000000>, <40000000>;
>>>> +                     assigned-clock-parents = <&pmc PMC_TYPE_CORE PMC_UTMI>, <&pmc PMC_TYPE_CORE PMC_UTMI>;
>>>> +                     bosch,mram-cfg = <0x7800 0 0 64 0 0 32 32>;
>>>> +                     status = "disabled";
>>>> +             };
>>>> +
>>>> +             tcb: timer@...08000 {
>>>> +                     compatible = "microchip,sam9x7-tcb","atmel,sama5d2-tcb", "simple-mfd", "syscon";
>>>
>>> Why this is simple-mfd without children?
>>
>> The tcb node will have each TC (Timer Counter) Block as a child when it
>> is configured to be used as either one of the following modes Timer or
>> Counter / Capture / PWM.
> 
> And where are these children? What does it mean "will have", in context
> when? DTS is static, if you do not have here children then this is not a
> simple-mfd.
> 
I understand your concern. But the thing is that, each tc block is 
configured as a child and it can be configured in 3 different modes with 
different compatibles. In the current dts (i.e., sam9x75_curiosity 
board) we don't have a use case for the tcb, hence there are no child 
nodes defined. But there are instances where it can be defined in the 
dts, say for a custom board using sam9x7 SoC. In that case the 
simple-mfd usage is justified, if I am not wrong. If this justification 
doesn't suffice, then declaring child nodes with one mode as default 
which can be overridden in the dts and kept disabled in the dtsi should 
be the other plausible way. Please let me know your suggestions.

> Best regards,
> Krzysztof
> 

-- 
Thanks and Regards,
Varshini Rajendran.