linux-kernel - Re: [PATCH 2/3] dt-bindings: interrupt-controller: RISC-V local interrupt controller docs

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Date:   Mon, 25 Jun 2018 22:04:48 +0200
From:   Christoph Böhmwalder <christoph@...hmwalder.at>
To:     Palmer Dabbelt <palmer@...ive.com>
Cc:     tglx@...utronix.de, jason@...edaemon.net, marc.zyngier@....com,
        robh+dt@...nel.org, mark.rutland@....com,
        devicetree@...r.kernel.org, aou@...s.berkeley.edu,
        linux-kernel@...r.kernel.org, Palmer Dabbelt <palmer@...belt.com>,
        linux-riscv@...ts.infradead.org, shorne@...il.com
Subject: Re: [PATCH 2/3] dt-bindings: interrupt-controller: RISC-V local
 interrupt controller docs

On Fri, Jun 22, 2018 at 04:20:05PM -0700, Palmer Dabbelt wrote:
> From: Palmer Dabbelt <palmer@...belt.com>
> 
> This patch adds documentation on the RISC-V local interrupt controller,
> which is a per-hart interrupt controller that manages all interrupts
> entering a RISC-V hart.  This interrupt controller is present on all
> RISC-V systems.
> 
> Signed-off-by: Palmer Dabbelt <palmer@...belt.com>
> ---
>  .../interrupt-controller/riscv,cpu-intc.txt        | 41 ++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/interrupt-controller/riscv,cpu-intc.txt
> 
> diff --git a/Documentation/devicetree/bindings/interrupt-controller/riscv,cpu-intc.txt b/Documentation/devicetree/bindings/interrupt-controller/riscv,cpu-intc.txt
> new file mode 100644
> index 000000000000..61900e2e3868
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/interrupt-controller/riscv,cpu-intc.txt
> @@ -0,0 +1,41 @@
> +RISC-V Hart-Level Interrupt Controller (HLIC)
> +---------------------------------------------
> +
> +RISC-V cores include Control Status Registers (CSRs) which are local to each
> +hart and can be read or written by software. Some of these CSRs are used to
> +control local interrupts connected to the core.  Every interrupt is ultimately
> +routed through a hart's HLIC before it interrupts that hart.
> +
> +The RISC-V supervisor ISA manual specifies three interrupt sources that are
> +attached to every HLIC: software interrupts, the timer interrupt, and external
> +interrupts.  Software interrupts are used to send IPIs between cores.  The
> +timer interrupt comes from an architecturally mandated real-time timer that is
> +controller via SBI calls and CSR reads.  External interrupts connect all other
> +device interrupts to the HLIC, which are routed via the platform-level
> +interrupt controller (PLIC).
> +
> +All RISC-V systems that conform to the supervisor ISA specification are
> +required to have a HLIC with these three interrupt sources present.  Since the
> +interrupt map is defined by the ISA it's not listed in the HLIC's device tree
> +entry, though external interrupt controllers (like the PLIC, for example) will
> +need to define how their interrupts map to the relevant HLICs.
> +
> +Required properties:
> +- compatible : "riscv,cpu-intc"
> +- #interrupt-cells : should be <1>
> +- interrupt-controller : Identifies the node as an interrupt controller
> +
> +Furthermore, this interrupt-controller MUST be embedded inside the cpu
> +definition of the hart whose CSRs control these local interrupts.
> +
> +An example device tree entry for a HLIC is show below.

Spotted a typo here, "show" -> "shown".

> +
> +	cpu1: cpu@1 {
> +		compatible = "riscv";
> +		...
> +		cpu1-intc: interrupt-controller {
> +			#interrupt-cells = <1>;
> +			compatible = "riscv,cpu-intc";
> +			interrupt-controller;
> +		};
> +	};
> -- 
> 2.16.4

Also, I've noticed that double spaces after punctuation are used pretty
inconsistently throughout the document. Is that intended?

--
Regards,
Christoph