Message-ID: <04abc8d6d8a9200e593f3f667a31ea0d3674c64b.camel@icenowy.me>
Date:   Mon, 05 Dec 2022 16:17:59 +0800
From:   Icenowy Zheng <uwu@...nowy.me>
To:     Samuel Holland <samuel@...lland.org>,
        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

在 2022-11-30星期三的 01:21 -0600，Samuel Holland写道：
> 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.

They're accessible but their interrupts are not, and I think this is
called d0_uart or uart3, but not uart0 at all.

> 
> > +                       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";

Using a single c900-plic here needs more discussion, I think.

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