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

From: Icenowy Zheng <uwu@icenowy.me>
To: Conor.Dooley@microchip.com, samuel@sholland.org, andre.przywara@arm.com
Cc: wens@csie.org, jernej.skrabec@gmail.com,
	linux-sunxi@lists.linux.dev, palmer@dabbelt.com,
	paul.walmsley@sifive.com, aou@eecs.berkeley.edu,
	linux-riscv@lists.infradead.org, robh+dt@kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	krzysztof.kozlowski+dt@linaro.org
Subject: Re: [PATCH 06/12] riscv: dts: allwinner: Add the D1 SoC base devicetree
Date: Sun, 21 Aug 2022 14:45:27 +0800	[thread overview]
Message-ID: <c6cba83ea9eea7fc41a9e78d0e45487b21f0f560.camel@icenowy.me> (raw)
In-Reply-To: <ff9e8bd3-c5f7-6319-060e-250151087a8e@microchip.com>

在 2022-08-20星期六的 17:29 +0000，Conor.Dooley@microchip.com写道：
> On 20/08/2022 18:24, Samuel Holland wrote:
> > On 8/15/22 12:01 PM, Conor.Dooley@microchip.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@sholland.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.

Well, maybe we can overuse the facility of C preprocessor?

e.g.

```
// For ARM
#define SOC_PERIPHERAL_IRQ(n) GIC_SPI n
// For RISC-V
#define SOC_PERIPHERAL_IRQ(n) n
```