linux-kernel - Re: [PATCH v5 1/2] arm64: dts: marvell: Add Armada 98DX2530 SoC and RD-AC5X board

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Date:   Tue, 10 May 2022 04:14:31 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will@...nel.org" <will@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "gregory.clement@...tlin.com" <gregory.clement@...tlin.com>,
        "sebastian.hesselbarth@...il.com" <sebastian.hesselbarth@...il.com>,
        "kostap@...vell.com" <kostap@...vell.com>,
        "robert.marko@...tura.hr" <robert.marko@...tura.hr>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 1/2] arm64: dts: marvell: Add Armada 98DX2530 SoC and
 RD-AC5X board

(resend without the html)


On 5/05/22 21:19, Krzysztof Kozlowski wrote:
>> +	core_clock: core_clock {
> No underscores in node names.
>
> All these clocks do not look like real clocks. Where are they if outside
> of SoC? These should be fed from clock controllers, shouldn't they? If
> they are provided by boards, don't put them into SoC...
>
>> +		compatible = "fixed-clock";
>> +		#clock-cells = <0>;
>> +		clock-frequency = <400000000>;
>> +	};
>> +
>> +	axi_clock: axi_clock {
>> +		compatible = "fixed-clock";
>> +		#clock-cells = <0>;
>> +		clock-frequency = <325000000>;
>> +	};
>> +
>> +	spi_clock: spi_clock {
>> +		compatible = "fixed-clock";
>> +		#clock-cells = <0>;
>> +		clock-frequency = <200000000>;
>> +	};

Based on the information I have (which isn't much) there is a ref_clk 
input that is connected to a 25MHz oscillator and then I'm assuming 
these are all generated from that with various dividers. 25MHz is the 
only documented option.

There doesn't appear to be any documented register where I can read out 
the divider ratios. It might be nice I could have the fixed osc node and 
have these 3 clocks derived with fixed divisors but I don't see any what 
of achieving that.