linux-kernel - Re: [PATCH 06/12] riscv: dts: allwinner: Add the D1 SoC base devicetree

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Date:   Sat, 20 Aug 2022 17:29:19 +0000
From:   <Conor.Dooley@...rochip.com>
To:     <samuel@...lland.org>, <Conor.Dooley@...rochip.com>,
        <andre.przywara@....com>
CC:     <wens@...e.org>, <jernej.skrabec@...il.com>,
        <linux-sunxi@...ts.linux.dev>, <palmer@...belt.com>,
        <paul.walmsley@...ive.com>, <aou@...s.berkeley.edu>,
        <linux-riscv@...ts.infradead.org>, <robh+dt@...nel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <krzysztof.kozlowski+dt@...aro.org>
Subject: Re: [PATCH 06/12] riscv: dts: allwinner: Add the D1 SoC base
 devicetree

On 20/08/2022 18:24, Samuel Holland wrote:
> On 8/15/22 12:01 PM, Conor.Dooley@...rochip.com wrote:
>> On 15/08/2022 14:11, Andre Przywara wrote:
>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>>
>>> On Mon, 15 Aug 2022 00:08:09 -0500
>>> Samuel Holland <samuel@...lland.org> wrote:
>>>
>>> Hi,
>>>
>>> thanks for all the efforts in getting those SoC peripherals supported!
>>>
>>>> D1 is a SoC containing a single-core T-HEAD Xuantie C906 CPU, as well as
>>>> one HiFi 4 DSP. The SoC is based on a design that additionally contained
>>>> a pair of Cortex A7's. For that reason, some peripherals are duplicated.
>>>
>>> So because of this, the Allwinner R528 and T113 SoCs would share almost
>>> everything in this file. Would it be useful to already split this DT up?
>>> To have a base .dtsi, basically this file without /cpus and /soc/plic,
>>> then have a RISC-V specific file with just those, including the base?
>>> There is precedence for this across-arch(-directories) sharing with the
>>> Raspberry Pi and Allwinner H3/H5 SoCs.
>>
>> For those playing along at home, one example is the arm64 bananapi m2
>> dts which looks like:
>>> /dts-v1/;
>>> #include "sun50i-h5.dtsi"
>>> #include "sun50i-h5-cpu-opp.dtsi"
>>> #include <arm/sunxi-bananapi-m2-plus-v1.2.dtsi>
>>>
>>> / {
>>> 	model = "Banana Pi BPI-M2-Plus v1.2 H5";
>>> 	compatible = "bananapi,bpi-m2-plus-v1.2", "allwinner,sun50i-h5";
>>> };
>>
>> I think this is a pretty good idea, and putting in the modularity up
>> front seems logical to me, so when the arm one does eventually get
>> added it can be done by only touching a single arch.
> 
> This is not feasible, due to the different #interrupt-cells. See
> https://lore.kernel.org/linux-riscv/CAMuHMdXHSMcrVOH+vcrdRRF+i2TkMcFisGxHMBPUEa8nTMFpzw@mail.gmail.com/
> 
> Even if we share some file across architectures, you still have to update files
> in both places to get the interrupts properties correct.
> 
> I get the desire to deduplicate things, but we already deal with updating the
> same/similar nodes across several SoCs, so that is nothing new. I think it would
> be more confusing/complicated to have all of the interrupts properties
> overridden in a separate file.

Yeah, should maybe have circled back after that conversation, would have been
nice but if the DTC can't do it nicely then w/e.