linux-kernel - Re: [PATCH v2 4/6] arm64: dts: axiado: Add initial support for AX3000 SoC and eval board

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Message-ID: <5163d9d8-d106-47f3-a0f9-0eaa01f15498@kernel.org>
Date: Sun, 22 Jun 2025 11:49:44 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Harshit Shah <hshah@...ado.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Linus Walleij <linus.walleij@...aro.org>,
 Bartosz Golaszewski <brgl@...ev.pl>, Arnd Bergmann <arnd@...db.de>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
Cc: "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
 "soc@...ts.linux.dev" <soc@...ts.linux.dev>
Subject: Re: [PATCH v2 4/6] arm64: dts: axiado: Add initial support for AX3000
 SoC and eval board

On 20/06/2025 23:18, Harshit Shah wrote:
> On 6/19/2025 11:08 PM, Krzysztof Kozlowski wrote:
>>>>> +
>>>>> +             spi_clk: spi_clk {
>>>>> +                     compatible = "fixed-clock";
>>>>> +                     #clock-cells = <0>;
>>>>> +                     clock-frequency = <25000000>;
>>>>> +             };
>>>>> +
>>>>> +             apb_pclk: apb_pclk {
>>>> No underscores in node names, but all these look incorrect - don't you
>>>> have clock controller?
>>> Noted, we will remove the "_" from the nodes. We do have clock
>>> controller however that is being accessed by other CPU before Linux will
>>> come-up.
>> What does it mean? Is the clock controller not available at all for
>> Linux or any other OS?
> 
> Apologies for the confusion. Yes, clock controller is available however 
> it is only accessible by another CPU which boots up before Linux comes up.
> 
> This another CPU is setting up the various output clocks (& PLLs) before 
> the Linux comes up.
> 
> So, that's the reason haven not added the clock controller in this DTS 
> but only will add fixed clocks.

And what happens if that other part decides to change frequencies?

Best regards,
Krzysztof