[PATCH v8 07/18] irqchip: RISC-V Local Interrupt Controller Driver

Palmer Dabbelt
2017-09-12T21:57:53Z

This patch adds a driver that manages the local interrupts on each
RISC-V hart, as specifiec by the RISC-V supervisor level ISA manual.
The local interrupt controller manages software interrupts, timer
interrupts, and hardware interrupts (which are routed via the
platform level interrupt controller). Per-hart local interrupt
controllers are found on all RISC-V systems.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
---
drivers/irqchip/Kconfig | 14 +++
drivers/irqchip/Makefile | 1 +
drivers/irqchip/irq-riscv-intc.c | 210 +++++++++++++++++++++++++++++++++++++++
3 files changed, 225 insertions(+)
create mode 100644 drivers/irqchip/irq-riscv-intc.c

diff --git a/drivers/irqchip/Kconfig b/drivers/irqchip/Kconfig
index f1fd5f44d1d4..7923d3fa8fae 100644
--- a/drivers/irqchip/Kconfig
+++ b/drivers/irqchip/Kconfig
@@ -306,3 +306,17 @@ config QCOM_IRQ_COMBINER
help
Say yes here to add support for the IRQ combiner devices embedded
in Qualcomm Technologies chips.
+
+config RISCV_INTC
+ def_bool y if RISCV
+ #bool "RISC-V Interrupt Controller"
+ depends on RISCV
+ default y
+ help
+ This enables support for the local interrupt controller found in
+ standard RISC-V systems. The local interrupt controller handles
+ timer interrupts, software interrupts, and hardware interrupts.
+ Without a local interrupt controller the system will be unable to
+ handle any interrupts, including those passed via the PLIC.
+
+ If you don't know what to do here, say Y.
diff --git a/drivers/irqchip/Makefile b/drivers/irqchip/Makefile
index e88d856cc09c..b1aa9114afc4 100644
--- a/drivers/irqchip/Makefile
+++ b/drivers/irqchip/Makefile
@@ -78,3 +78,4 @@ obj-$(CONFIG_EZNPS_GIC) += irq-eznps.o
obj-$(CONFIG_ARCH_ASPEED) += irq-aspeed-vic.o irq-aspeed-i2c-ic.o
obj-$(CONFIG_STM32_EXTI) += irq-stm32-exti.o
obj-$(CONFIG_QCOM_IRQ_COMBINER) += qcom-irq-combiner.o
+obj-$(CONFIG_RISCV_INTC) += irq-riscv-intc.o
diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
new file mode 100644
index 000000000000..d019bd3a4ae3
--- /dev/null
+++ b/drivers/irqchip/irq-riscv-intc.c
@@ -0,0 +1,210 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, version 2.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/irq.h>
+#include <linux/irqchip.h>
+#include <linux/irqdomain.h>
+#include <linux/interrupt.h>
+#include <linux/ftrace.h>
+#include <linux/of.h>
+#include <linux/seq_file.h>
+
+#include <asm/ptrace.h>
+#include <asm/sbi.h>
+#include <asm/smp.h>
+
+#define PTR_BITS (8 * sizeof(uintptr_t))
+
+struct riscv_irq_data {
+ struct irq_chip chip;
+ struct irq_domain *domain;
+ int hart;
+ char name[20];
+};
+DEFINE_PER_CPU(struct riscv_irq_data, riscv_irq_data);
+
+static void riscv_software_interrupt(void)
+{
+#ifdef CONFIG_SMP
+ irqreturn_t ret;
+
+ ret = handle_ipi();
+
+ WARN_ON(ret == IRQ_NONE);
+#else
+ /*
+ * We currently only use software interrupts to pass inter-processor
+ * interrupts, so if a non-SMP system gets a software interrupt then we
+ * don't know what to do.
+ */
+ pr_warning("Software Interrupt without CONFIG_SMP\n");
+#endif
+}
+
+asmlinkage void __irq_entry do_IRQ(unsigned int cause, struct pt_regs *regs)
+{
+ struct pt_regs *old_regs = set_irq_regs(regs);
+ struct irq_domain *domain;
+
+ irq_enter();
+
+ /*
+ * There are three classes of interrupt: timer, software, and
+ * external devices. We dispatch between them here. External
+ * device interrupts use the generic IRQ mechanisms.
+ */
+ switch (cause) {
+ case INTERRUPT_CAUSE_TIMER:
+ riscv_timer_interrupt();
+ break;
+ case INTERRUPT_CAUSE_SOFTWARE:
+ riscv_software_interrupt();
+ break;
+ default:
+ domain = per_cpu(riscv_irq_data, smp_processor_id()).domain;
+ generic_handle_irq(irq_find_mapping(domain, cause));
+ break;
+ }
+
+ irq_exit();
+ set_irq_regs(old_regs);
+}
+
+static int riscv_irqdomain_map(struct irq_domain *d, unsigned int irq,
+ irq_hw_number_t hwirq)
+{
+ struct riscv_irq_data *data = d->host_data;
+
+ irq_set_chip_and_handler(irq, &data->chip, handle_simple_irq);
+ irq_set_chip_data(irq, data);
+ irq_set_noprobe(irq);
+ irq_set_affinity(irq, cpumask_of(data->hart));
+
+ return 0;
+}
+
+static const struct irq_domain_ops riscv_irqdomain_ops = {
+ .map = riscv_irqdomain_map,
+ .xlate = irq_domain_xlate_onecell,
+};
+
+/*
+ * 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. They are only called internally to this module, so they BUG_ON if
+ * this condition is violated rather than attempting to handle the error by
+ * forwarding to the target hart, as that's already expected to have been done.
+ */
+static void riscv_irq_mask(struct irq_data *d)
+{
+ struct riscv_irq_data *data = irq_data_get_irq_chip_data(d);
+
+ BUG_ON(smp_processor_id() != data->hart);
+ csr_clear(sie, 1 << (long)d->hwirq);
+}
+
+static void riscv_irq_unmask(struct irq_data *d)
+{
+ struct riscv_irq_data *data = irq_data_get_irq_chip_data(d);
+
+ BUG_ON(smp_processor_id() != data->hart);
+ csr_set(sie, 1 << (long)d->hwirq);
+}
+
+/* Callbacks for twiddling SIE on another hart. */
+static void riscv_irq_enable_helper(void *d)
+{
+ riscv_irq_unmask(d);
+}
+
+static void riscv_irq_disable_helper(void *d)
+{
+ riscv_irq_mask(d);
+}
+
+static void riscv_remote_ctrl(unsigned int cpu, void (*fn)(void *d),
+ struct irq_data *data)
+{
+ smp_call_function_single(cpu, fn, data, true);
+}
+
+static void riscv_irq_enable(struct irq_data *d)
+{
+ struct riscv_irq_data *data = irq_data_get_irq_chip_data(d);
+
+ /*
+ * It's only possible to write SIE on the current hart. This jumps
+ * over to the target hart if it's not the current one. It's invalid
+ * to write SIE on a hart that's not currently running.
+ */
+ if (data->hart == smp_processor_id())
+ riscv_irq_unmask(d);
+ else if (cpu_online(data->hart))
+ riscv_remote_ctrl(data->hart, riscv_irq_enable_helper, d);
+ else
+ WARN_ON_ONCE(1);
+}
+
+static void riscv_irq_disable(struct irq_data *d)
+{
+ struct riscv_irq_data *data = irq_data_get_irq_chip_data(d);
+
+ /*
+ * It's only possible to write SIE on the current hart. This jumps
+ * over to the target hart if it's not the current one. It's invalid
+ * to write SIE on a hart that's not currently running.
+ */
+ if (data->hart == smp_processor_id())
+ riscv_irq_mask(d);
+ else if (cpu_online(data->hart))
+ riscv_remote_ctrl(data->hart, riscv_irq_disable_helper, d);
+ else
+ WARN_ON_ONCE(1);
+}
+
+static int riscv_intc_init(struct device_node *node, struct device_node *parent)
+{
+ int hart;
+ struct riscv_irq_data *data;
+
+ if (parent)
+ return 0;
+
+ hart = riscv_of_processor_hart(node->parent);
+ if (hart < 0)
+ return -EIO;
+
+ data = &per_cpu(riscv_irq_data, hart);
+ snprintf(data->name, sizeof(data->name), "riscv,cpu_intc,%d", hart);
+ data->hart = hart;
+ data->chip.name = data->name;
+ data->chip.irq_mask = riscv_irq_mask;
+ data->chip.irq_unmask = riscv_irq_unmask;
+ data->chip.irq_enable = riscv_irq_enable;
+ data->chip.irq_disable = riscv_irq_disable;
+ data->domain = irq_domain_add_linear(node, PTR_BITS,
+ &riscv_irqdomain_ops, data);
+ if (!data->domain)
+ goto error_add_linear;
+ pr_info("%s: %d local interrupts mapped\n", data->name, PTR_BITS);
+ return 0;
+
+error_add_linear:
+ pr_warning("%s: unable to add IRQ domain\n",
+ data->name);
+ return -ENXIO;
+}
+
+IRQCHIP_DECLARE(riscv, "riscv,cpu-intc", riscv_intc_init);
--
2.13.5