linux-kernel - Re: [PATCH v2 06/16] arm64: dts: st: add LPDDR channel to stm32mp257f-dk board

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Message-ID: <ae960a16-65ad-4b22-b9fb-89efbffacd3e@foss.st.com>
Date: Tue, 15 Jul 2025 10:32:09 +0200
From: Clement LE GOFFIC <clement.legoffic@...s.st.com>
To: Rob Herring <robh@...nel.org>
CC: Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue
	<alexandre.torgue@...s.st.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Jonathan Corbet <corbet@....net>,
        Gatien Chevallier
	<gatien.chevallier@...s.st.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Gabriel Fernandez
	<gabriel.fernandez@...s.st.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Le
 Goffic <legoffic.clement@...il.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-perf-users@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>,
        <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v2 06/16] arm64: dts: st: add LPDDR channel to
 stm32mp257f-dk board

Hi Rob,

Thanks for the review !

On 7/15/25 05:20, Rob Herring wrote:
> On Fri, Jul 11, 2025 at 04:48:58PM +0200, Clément Le Goffic wrote:
>> Add 32bits LPDDR4 channel to the stm32mp257f-dk board.
>>
>> Signed-off-by: Clément Le Goffic <clement.legoffic@...s.st.com>
>> ---
>>   arch/arm64/boot/dts/st/stm32mp257f-dk.dts | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/arch/arm64/boot/dts/st/stm32mp257f-dk.dts b/arch/arm64/boot/dts/st/stm32mp257f-dk.dts
>> index a278a1e3ce03..a97b41f14ecc 100644
>> --- a/arch/arm64/boot/dts/st/stm32mp257f-dk.dts
>> +++ b/arch/arm64/boot/dts/st/stm32mp257f-dk.dts
>> @@ -54,6 +54,13 @@ led-blue {
>>   		};
>>   	};
>>   
>> +	lpddr_channel: lpddr4-channel {
>> +		#address-cells = <1>;
>> +		#size-cells = <0>;
>> +		compatible = "jedec,lpddr4-channel";
> 
> Not tested because this doesn't match the binding.

Hmm, I've tested with make dtbs_check and dt_binding_check and it didn't 
complain on my side.
What I have miss ?


> 
>> +		io-width = <32>;
>> +	};
> 
> What would multiple channels look like? I think this needs some work.
> Like it should perhaps be within the memory node. It's a lot to just say
> 32-bit LPDDR4 x1.

I guess something like two channels node following each other in the DT.
It can be in the memory node I don't know what are the stakes here.
I was inspired by the lpddr node here:
arch/arm/boot/dts/samsung/exynos5422-odroid-core.dtsi:336

Best regard,
Clément