linux-kernel - [PATCH v8 03/18] dt-bindings: interrupt-controller: RISC-V local interrupt controller docs

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Date:   Tue, 12 Sep 2017 14:57:00 -0700
From:   Palmer Dabbelt <palmer@...belt.com>
To:     peterz@...radead.org, tglx@...utronix.de, jason@...edaemon.net,
        marc.zyngier@....com, Arnd Bergmann <arnd@...db.de>,
        dmitriy@...-tech.org
Cc:     yamada.masahiro@...ionext.com, mmarek@...e.com, albert@...ive.com,
        will.deacon@....com, boqun.feng@...il.com, oleg@...hat.com,
        mingo@...hat.com, daniel.lezcano@...aro.org,
        gregkh@...uxfoundation.org, jslaby@...e.com, davem@...emloft.net,
        mchehab@...nel.org, hverkuil@...all.nl, rdunlap@...radead.org,
        viro@...iv.linux.org.uk, mhiramat@...nel.org, fweisbec@...il.com,
        mcgrof@...nel.org, dledford@...hat.com, bart.vanassche@...disk.com,
        sstabellini@...nel.org, mpe@...erman.id.au,
        rmk+kernel@...linux.org.uk, paul.gortmaker@...driver.com,
        nicolas.dichtel@...nd.com, linux@...ck-us.net,
        heiko.carstens@...ibm.com, schwidefsky@...ibm.com,
        geert@...ux-m68k.org, akpm@...ux-foundation.org,
        andriy.shevchenko@...ux.intel.com, jiri@...lanox.com,
        vgupta@...opsys.com, airlied@...hat.com, jk@...abs.org,
        chris@...is-wilson.co.uk, Jason@...c4.com,
        paulmck@...ux.vnet.ibm.com, ncardwell@...gle.com,
        linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        patches@...ups.riscv.org, Palmer Dabbelt <palmer@...belt.com>
Subject: [PATCH v8 03/18] dt-bindings: interrupt-controller: RISC-V local interrupt controller docs

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.
+
+	cpu1: cpu@1 {
+		compatible = "riscv";
+		...
+		cpu1-intc: interrupt-controller {
+			#interrupt-cells = <1>;
+			compatible = "riscv,cpu-intc";
+			interrupt-controller;
+		};
+	};
-- 
2.13.5