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Subject[PATCH v5 3/6] irqchip: RISC-V per-HART local interrupt controller driver
Date
The RISC-V per-HART local interrupt controller manages software
interrupts, timer interrupts, external interrupts (which are routed
via the platform level interrupt controller) and other per-HART
local interrupts.

This patch adds a driver for the RISC-V local interrupt controller.
It is a major re-write over perviously submitted version.
(Refer, https://www.spinics.net/lists/devicetree/msg241230.html)

Few advantages of this new driver over previous one are:
1. All local interrupts are registered as per-CPU interrupts
2. The RISC-V timer driver can register timer interrupt handler
using kernel irq subsystem without relying on arch/riscv to
explicitly call it's interrupt handler
3. The KVM RISC-V can use this driver to implement interrupt
handler for per-HART guest external interrupt defined by
the RISC-V H-Extension
4. In future, we can develop drivers for devices with per-HART
interrupts without changing arch code or this driver (example,
CLINT timer driver for RISC-V M-mode kernel)

The RISC-V INTC driver is compliant with RISC-V Hart-Level Interrupt
Controller DT bindings located at:
Documentation/devicetree/bindings/interrupt-controller/riscv,cpu-intc.txt

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/irq.h | 2 -
arch/riscv/kernel/irq.c | 33 +-----
arch/riscv/kernel/traps.c | 2 -
drivers/irqchip/Kconfig | 13 ++
drivers/irqchip/Makefile | 1 +
drivers/irqchip/irq-riscv-intc.c | 158 +++++++++++++++++++++++++
drivers/irqchip/irq-sifive-plic.c | 38 +++++-
include/linux/cpuhotplug.h | 1 +
include/linux/irqchip/irq-riscv-intc.h | 20 ++++
10 files changed, 229 insertions(+), 40 deletions(-)
create mode 100644 drivers/irqchip/irq-riscv-intc.c
create mode 100644 include/linux/irqchip/irq-riscv-intc.h

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 90a008e28f7e..822cb0e1a380 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -40,6 +40,7 @@ config RISCV
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
select HAVE_SYSCALL_TRACEPOINTS
+ select HANDLE_DOMAIN_IRQ
select IRQ_DOMAIN
select SPARSE_IRQ
select SYSCTL_EXCEPTION_TRACE
diff --git a/arch/riscv/include/asm/irq.h b/arch/riscv/include/asm/irq.h
index 0183e15ace66..a9e5f07a7e9c 100644
--- a/arch/riscv/include/asm/irq.h
+++ b/arch/riscv/include/asm/irq.h
@@ -10,8 +10,6 @@
#include <linux/interrupt.h>
#include <linux/linkage.h>

-#define NR_IRQS 0
-
void riscv_timer_interrupt(void);

#include <asm-generic/irq.h>
diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
index bb0bfcd537e7..eb8777642ce6 100644
--- a/arch/riscv/kernel/irq.c
+++ b/arch/riscv/kernel/irq.c
@@ -7,7 +7,6 @@

#include <linux/interrupt.h>
#include <linux/irqchip.h>
-#include <linux/irqdomain.h>
#include <linux/seq_file.h>
#include <asm/smp.h>

@@ -19,39 +18,13 @@ int arch_show_interrupts(struct seq_file *p, int prec)

asmlinkage __visible void __irq_entry do_IRQ(struct pt_regs *regs)
{
- struct pt_regs *old_regs;
-
- switch (regs->cause & ~CAUSE_IRQ_FLAG) {
- case RV_IRQ_TIMER:
- old_regs = set_irq_regs(regs);
- irq_enter();
- riscv_timer_interrupt();
- irq_exit();
- set_irq_regs(old_regs);
- break;
-#ifdef CONFIG_SMP
- case RV_IRQ_SOFT:
- /*
- * We only use software interrupts to pass IPIs, so if a non-SMP
- * system gets one, then we don't know what to do.
- */
- handle_IPI(regs);
- break;
-#endif
- case RV_IRQ_EXT:
- old_regs = set_irq_regs(regs);
- irq_enter();
+ if (handle_arch_irq)
handle_arch_irq(regs);
- irq_exit();
- set_irq_regs(old_regs);
- break;
- default:
- pr_alert("unexpected interrupt cause 0x%lx", regs->cause);
- BUG();
- }
}

void __init init_IRQ(void)
{
irqchip_init();
+ if (!handle_arch_irq)
+ panic("No interrupt controller found.");
}
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 7f58fa53033f..f48c76aadbf3 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -178,6 +178,4 @@ void trap_init(void)
csr_write(CSR_SCRATCH, 0);
/* Set the exception vector address */
csr_write(CSR_TVEC, &handle_exception);
- /* Enable interrupts */
- csr_write(CSR_IE, IE_SIE);
}
diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index a85aada04a64..95d6137a8117 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -493,6 +493,19 @@ config TI_SCI_INTA_IRQCHIP
If you wish to use interrupt aggregator irq resources managed by the
TI System Controller, say Y here. Otherwise, say N.

+config RISCV_INTC
+ bool "RISC-V Local Interrupt Controller"
+ depends on RISCV
+ default y
+ help
+ This enables support for the per-HART local interrupt controller
+ found in standard RISC-V systems. The per-HART local interrupt
+ controller handles timer interrupts, software interrupts, and
+ hardware interrupts. Without a per-HART local interrupt controller,
+ a RISC-V system will be unable to handle any interrupts.
+
+ If you don't know what to do here, say Y.
+
config SIFIVE_PLIC
bool "SiFive Platform-Level Interrupt Controller"
depends on RISCV
diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
index 37bbe39bf909..b8319f045472 100644
--- a/drivers/irqchip/Makefile
+++ b/drivers/irqchip/Makefile
@@ -98,6 +98,7 @@ obj-$(CONFIG_NDS32) += irq-ativic32.o
obj-$(CONFIG_QCOM_PDC) += qcom-pdc.o
obj-$(CONFIG_CSKY_MPINTC) += irq-csky-mpintc.o
obj-$(CONFIG_CSKY_APB_INTC) += irq-csky-apb-intc.o
+obj-$(CONFIG_RISCV_INTC) += irq-riscv-intc.o
obj-$(CONFIG_SIFIVE_PLIC) += irq-sifive-plic.o
obj-$(CONFIG_IMX_IRQSTEER) += irq-imx-irqsteer.o
obj-$(CONFIG_IMX_INTMUX) += irq-imx-intmux.o
diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
new file mode 100644
index 000000000000..2f364e6a87f9
--- /dev/null
+++ b/drivers/irqchip/irq-riscv-intc.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017-2018 SiFive
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ */
+
+#define pr_fmt(fmt) "riscv-intc: " fmt
+#include <linux/atomic.h>
+#include <linux/bits.h>
+#include <linux/cpu.h>
+#include <linux/irq.h>
+#include <linux/irqchip.h>
+#include <linux/irqchip/irq-riscv-intc.h>
+#include <linux/irqdomain.h>
+#include <linux/interrupt.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/smp.h>
+
+static struct device_node *intc_domain_node;
+static struct irq_domain *intc_domain;
+
+static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
+{
+ struct pt_regs *old_regs;
+ unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;
+
+ if (unlikely(cause >= BITS_PER_LONG))
+ panic("unexpected interrupt cause");
+
+ switch (cause) {
+ case RV_IRQ_TIMER:
+ old_regs = set_irq_regs(regs);
+ irq_enter();
+ riscv_timer_interrupt();
+ irq_exit();
+ set_irq_regs(old_regs);
+ break;
+#ifdef CONFIG_SMP
+ case RV_IRQ_SOFT:
+ /*
+ * We only use software interrupts to pass IPIs, so if a
+ * non-SMP system gets one, then we don't know what to do.
+ */
+ handle_IPI(regs);
+ break;
+#endif
+ default:
+ handle_domain_irq(intc_domain, cause, regs);
+ break;
+ }
+}
+
+/*
+ * On RISC-V systems local interrupts are masked or unmasked by writing
+ * the SIE (Supervisor Interrupt Enable) CSR. As CSRs can only be written
+ * on the local hart, these functions can only be called on the hart that
+ * corresponds to the IRQ chip.
+ */
+
+static void riscv_intc_irq_mask(struct irq_data *d)
+{
+ csr_clear(CSR_IE, 1 << (long)d->hwirq);
+}
+
+static void riscv_intc_irq_unmask(struct irq_data *d)
+{
+ csr_set(CSR_IE, 1 << (long)d->hwirq);
+}
+
+static int riscv_intc_cpu_starting(unsigned int cpu)
+{
+ csr_write(CSR_IE, 1UL << RV_IRQ_SOFT);
+ csr_write(CSR_IP, 0);
+ return 0;
+}
+
+static int riscv_intc_cpu_dying(unsigned int cpu)
+{
+ csr_clear(CSR_IE, 1UL << RV_IRQ_SOFT);
+ return 0;
+}
+
+static struct irq_chip riscv_intc_chip = {
+ .name = "RISC-V INTC",
+ .irq_mask = riscv_intc_irq_mask,
+ .irq_unmask = riscv_intc_irq_unmask,
+};
+
+static int riscv_intc_domain_map(struct irq_domain *d, unsigned int irq,
+ irq_hw_number_t hwirq)
+{
+ irq_set_percpu_devid(irq);
+ irq_domain_set_info(d, irq, hwirq, &riscv_intc_chip, d->host_data,
+ handle_percpu_devid_irq, NULL, NULL);
+ irq_set_status_flags(irq, IRQ_NOAUTOEN);
+
+ return 0;
+}
+
+static const struct irq_domain_ops riscv_intc_domain_ops = {
+ .map = riscv_intc_domain_map,
+ .xlate = irq_domain_xlate_onecell,
+};
+
+/* Get the OF device node used by INTC irq domain */
+struct device_node *riscv_of_intc_domain_node(void)
+{
+ return intc_domain_node;
+}
+EXPORT_SYMBOL_GPL(riscv_of_intc_domain_node);
+
+static int __init riscv_intc_init(struct device_node *node,
+ struct device_node *parent)
+{
+ int hartid;
+
+ /*
+ * The DT will have one INTC DT node under each CPU (or HART)
+ * DT node so riscv_intc_init() function will be called once
+ * for each INTC DT node. We only need INTC initialization for
+ * the INTC DT node belonging to boot CPU (or boot HART).
+ */
+ hartid = riscv_of_parent_hartid(node);
+ if (hartid < 0)
+ return 0;
+ if (riscv_hartid_to_cpuid(hartid) != smp_processor_id())
+ return 0;
+
+ intc_domain = irq_domain_add_linear(node, BITS_PER_LONG,
+ &riscv_intc_domain_ops, NULL);
+ if (!intc_domain)
+ goto error_add_linear;
+
+ /*
+ * We save the DT node used for creating irq domain and provide
+ * it to other drivers using iscv_of_intc_domain_node() function.
+ */
+ intc_domain_node = of_node_get(node);
+
+ set_handle_irq(&riscv_intc_irq);
+
+ cpuhp_setup_state(CPUHP_AP_IRQ_RISCV_STARTING,
+ "irqchip/riscv/intc:starting",
+ riscv_intc_cpu_starting,
+ riscv_intc_cpu_dying);
+
+ pr_info("%lu local interrupts mapped\n", (long)BITS_PER_LONG);
+
+ return 0;
+
+error_add_linear:
+ pr_warn("unable to add IRQ domain\n");
+ return -ENXIO;
+}
+
+IRQCHIP_DECLARE(riscv, "riscv,cpu-intc", riscv_intc_init);
diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
index 16d31d114c30..4f9b2877aa9d 100644
--- a/drivers/irqchip/irq-sifive-plic.c
+++ b/drivers/irqchip/irq-sifive-plic.c
@@ -9,6 +9,8 @@
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/irqchip.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/irqchip/irq-riscv-intc.h>
#include <linux/irqdomain.h>
#include <linux/module.h>
#include <linux/of.h>
@@ -60,6 +62,7 @@
#define PLIC_ENABLE_THRESHOLD 0

struct plic_priv {
+ int parent_irq;
struct cpumask lmask;
struct irq_domain *irqdomain;
void __iomem *regs;
@@ -219,15 +222,17 @@ static const struct irq_domain_ops plic_irqdomain_ops = {
* that source ID back to the same claim register. This automatically enables
* and disables the interrupt, so there's nothing else to do.
*/
-static void plic_handle_irq(struct pt_regs *regs)
+static void plic_handle_irq(struct irq_desc *desc)
{
struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
+ struct irq_chip *chip = irq_desc_get_chip(desc);
void __iomem *claim = handler->hart_base + CONTEXT_CLAIM;
irq_hw_number_t hwirq;

WARN_ON_ONCE(!handler->present);

- csr_clear(CSR_IE, IE_EIE);
+ chained_irq_enter(chip, desc);
+
while ((hwirq = readl(claim))) {
int irq = irq_find_mapping(handler->priv->irqdomain, hwirq);

@@ -237,7 +242,8 @@ static void plic_handle_irq(struct pt_regs *regs)
else
generic_handle_irq(irq);
}
- csr_set(CSR_IE, IE_EIE);
+
+ chained_irq_exit(chip, desc);
}

static void plic_set_threshold(struct plic_handler *handler, u32 threshold)
@@ -250,7 +256,8 @@ static int plic_dying_cpu(unsigned int cpu)
{
struct plic_handler *handler = this_cpu_ptr(&plic_handlers);

- csr_clear(CSR_IE, IE_EIE);
+ if (handler->priv->parent_irq)
+ disable_percpu_irq(handler->priv->parent_irq);
plic_set_threshold(handler, PLIC_DISABLE_THRESHOLD);

return 0;
@@ -259,8 +266,10 @@ static int plic_dying_cpu(unsigned int cpu)
static int plic_starting_cpu(unsigned int cpu)
{
struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
+ int pirq = handler->priv->parent_irq;

- csr_set(CSR_IE, IE_EIE);
+ if (pirq)
+ enable_percpu_irq(pirq, irq_get_trigger_type(pirq));
plic_set_threshold(handler, PLIC_ENABLE_THRESHOLD);

return 0;
@@ -273,6 +282,7 @@ static int __init plic_init(struct device_node *node,
u32 nr_irqs;
struct plic_priv *priv;
struct plic_handler *handler;
+ struct of_phandle_args intc_args;

priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (!priv)
@@ -354,6 +364,23 @@ static int __init plic_init(struct device_node *node,
nr_handlers++;
}

+ /*
+ * We can have multiple PLIC instances so setup chained handler
+ * for all PLIC instances.
+ */
+ intc_args.np = riscv_of_intc_domain_node();
+ intc_args.args_count = 1;
+ intc_args.args[0] = RV_IRQ_EXT;
+ priv->parent_irq = irq_create_of_mapping(&intc_args);
+ if (priv->parent_irq)
+ irq_set_chained_handler(priv->parent_irq,
+ plic_handle_irq);
+ else {
+ pr_err("%pOFP: intc mapping failed\n", node);
+ error = -ENODEV;
+ goto out_iounmap;
+ }
+
/*
* We can have multiple PLIC instances so setup cpuhp state only
* when context handler for current/boot CPU is present.
@@ -368,7 +395,6 @@ static int __init plic_init(struct device_node *node,

pr_info("%pOFP: mapped %d interrupts with %d handlers for"
" %d contexts.\n", node, nr_irqs, nr_handlers, nr_contexts);
- set_handle_irq(plic_handle_irq);
return 0;

out_iounmap:
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 77d70b633531..57b1f8f777d9 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -102,6 +102,7 @@ enum cpuhp_state {
CPUHP_AP_IRQ_ARMADA_XP_STARTING,
CPUHP_AP_IRQ_BCM2836_STARTING,
CPUHP_AP_IRQ_MIPS_GIC_STARTING,
+ CPUHP_AP_IRQ_RISCV_STARTING,
CPUHP_AP_IRQ_SIFIVE_PLIC_STARTING,
CPUHP_AP_ARM_MVEBU_COHERENCY,
CPUHP_AP_MICROCODE_LOADER,
diff --git a/include/linux/irqchip/irq-riscv-intc.h b/include/linux/irqchip/irq-riscv-intc.h
new file mode 100644
index 000000000000..b11d38353099
--- /dev/null
+++ b/include/linux/irqchip/irq-riscv-intc.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ */
+
+#ifndef __INCLUDE_LINUX_IRQCHIP_IRQ_RISCV_INTC_H
+#define __INCLUDE_LINUX_IRQCHIP_IRQ_RISCV_INTC_H
+
+struct device_node;
+
+#ifdef CONFIG_RISCV_INTC
+struct device_node *riscv_of_intc_domain_node(void);
+#else
+static inline struct device_node *riscv_of_intc_domain_node(void)
+{
+ return NULL;
+}
+#endif
+
+#endif
--
2.25.1
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