linux-kernel - Re: [PATCH v2 6/9] riscv: dts: bouffalolab: add the bl808 SoC base device tree

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Date:   Wed, 30 Nov 2022 01:21:27 -0600
From:   Samuel Holland <samuel@...lland.org>
To:     Jisheng Zhang <jszhang@...nel.org>
Cc:     linux-riscv@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Conor Dooley <conor@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Subject: Re: [PATCH v2 6/9] riscv: dts: bouffalolab: add the bl808 SoC base
 device tree

On 11/27/22 07:24, Jisheng Zhang wrote:
> Add a baisc dtsi for the bouffalolab bl808 SoC.
> 
> Signed-off-by: Jisheng Zhang <jszhang@...nel.org>
> ---
>  arch/riscv/boot/dts/bouffalolab/bl808.dtsi | 74 ++++++++++++++++++++++
>  1 file changed, 74 insertions(+)
>  create mode 100644 arch/riscv/boot/dts/bouffalolab/bl808.dtsi
> 
> diff --git a/arch/riscv/boot/dts/bouffalolab/bl808.dtsi b/arch/riscv/boot/dts/bouffalolab/bl808.dtsi
> new file mode 100644
> index 000000000000..f4b170ccc32e
> --- /dev/null
> +++ b/arch/riscv/boot/dts/bouffalolab/bl808.dtsi
> @@ -0,0 +1,74 @@
> +// SPDX-License-Identifier: (GPL-2.0+ or MIT)
> +/*
> + * Copyright (C) 2022 Jisheng Zhang <jszhang@...nel.org>
> + */
> +
> +#include <dt-bindings/interrupt-controller/irq.h>
> +
> +/ {
> +	compatible = "bouffalolab,bl808";
> +	#address-cells = <1>;
> +	#size-cells = <1>;
> +
> +	cpus {
> +		timebase-frequency = <1000000>;
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +
> +		cpu0: cpu@0 {
> +			compatible = "thead,c906", "riscv";
> +			device_type = "cpu";
> +			reg = <0>;
> +			d-cache-block-size = <64>;
> +			d-cache-sets = <256>;
> +			d-cache-size = <32768>;
> +			i-cache-block-size = <64>;
> +			i-cache-sets = <128>;
> +			i-cache-size = <32768>;
> +			mmu-type = "riscv,sv39";
> +			riscv,isa = "rv64imafdc";
> +
> +			cpu0_intc: interrupt-controller {
> +				compatible = "riscv,cpu-intc";
> +				interrupt-controller;
> +				#address-cells = <0>;
> +				#interrupt-cells = <1>;
> +			};
> +		};
> +	};
> +
> +	xtal: xtal-clk {
> +		compatible = "fixed-clock";
> +		#clock-cells = <0>;
> +		/* This value must be overridden by the board */
> +		clock-frequency = <0>;
> +	};
> +
> +	soc {
> +		compatible = "simple-bus";
> +		ranges;
> +		interrupt-parent = <&plic>;
> +		dma-noncoherent;
> +		#address-cells = <1>;
> +		#size-cells = <1>;
> +
> +		uart0: serial@...02000 {

It's unfortunate that the SDK/documentation calls this peripheral both
UART0 and UART3. I don't know if we can/should put the "M0" and "D0" bus
peripherals in the same DT; it seems like most of the "M0" peripherals
are not accessible from the C906. But if we did, this would conflict
with the other UART0.

> +			compatible = "bouffalolab,bl808-uart";
> +			reg = <0x30002000 0x1000>;
> +			interrupts = <20 IRQ_TYPE_LEVEL_HIGH>;
> +			clocks = <&xtal>;

There's a clock controller with a mux and a gate between the crystal and
the UART. I'm not sure what the policy is about adding "fake" suppliers
before the real supplier has a binding defined.

Unfortunately, Bouffalolab threw everything and the kitchen sink into
the GLB register space, so that complicates defining the binding for the
clock/reset controller part.

> +			status = "disabled";
> +		};
> +
> +		plic: interrupt-controller@...00000 {
> +			compatible = "thead,c900-plic";
> +			reg = <0xe0000000 0x4000000>;
> +			interrupts-extended = <&cpu0_intc 0xffffffff>,

The C906 PLIC has an M-mode context, so 0xffffffff is not correct. This
should reference the M-mode external interrupt.

> +					      <&cpu0_intc 9>;
> +			interrupt-controller;
> +			#address-cells = <0>;
> +			#interrupt-cells = <2>;
> +			riscv,ndev = <64>;

The SDK/documentation lists IRQ numbers up to BL808_IRQ_PDS == 82, so
this value should be at least that.

Regards,
Samuel

> +		};
> +	};
> +};