irq-sifive-plic.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2017 SiFive
 * Copyright (C) 2018 Christoph Hellwig
 */
#define pr_fmt(fmt) "plic: " fmt
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/irqchip.h>
#include <linux/irqdomain.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <asm/smp.h>

/*
 * This driver implements a version of the RISC-V PLIC with the actual layout
 * specified in chapter 8 of the SiFive U5 Coreplex Series Manual:
 *
 *     https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf
 *
 * The largest number supported by devices marked as 'sifive,plic-1.0.0', is
 * 1024, of which device 0 is defined as non-existent by the RISC-V Privileged
 * Spec.
 */

#define MAX_DEVICES			1024
#define MAX_CONTEXTS			15872

/*
 * Each interrupt source has a priority register associated with it.
 * We always hardwire it to one in Linux.
 */
#define PRIORITY_BASE			0
#define     PRIORITY_PER_ID		4

/*
 * Each hart context has a vector of interrupt enable bits associated with it.
 * There's one bit for each interrupt source.
 */
#define ENABLE_BASE			0x2000
#define     ENABLE_PER_HART		0x80

/*
 * Each hart context has a set of control registers associated with it.  Right
 * now there's only two: a source priority threshold over which the hart will
 * take an interrupt, and a register to claim interrupts.
 */
#define CONTEXT_BASE			0x200000
#define     CONTEXT_PER_HART		0x1000
#define     CONTEXT_THRESHOLD		0x00
#define     CONTEXT_CLAIM		0x04

static void __iomem *plic_regs;

struct plic_handler {
	bool			present;
	void __iomem		*hart_base;
	/*
	 * Protect mask operations on the registers given that we can't
	 * assume atomic memory operations work on them.
	 */
	raw_spinlock_t		enable_lock;
	void __iomem		*enable_base;
};
static DEFINE_PER_CPU(struct plic_handler, plic_handlers);

static inline void plic_toggle(struct plic_handler *handler,
				int hwirq, int enable)
{
	u32 __iomem *reg = handler->enable_base + (hwirq / 32) * sizeof(u32);
	u32 hwirq_mask = 1 << (hwirq % 32);

	raw_spin_lock(&handler->enable_lock);
	if (enable)
		writel(readl(reg) | hwirq_mask, reg);
	else
		writel(readl(reg) & ~hwirq_mask, reg);
	raw_spin_unlock(&handler->enable_lock);
}

static inline void plic_irq_toggle(const struct cpumask *mask,
				   int hwirq, int enable)
{
	int cpu;

	writel(enable, plic_regs + PRIORITY_BASE + hwirq * PRIORITY_PER_ID);
	for_each_cpu(cpu, mask) {
		struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);

		if (handler->present)
			plic_toggle(handler, hwirq, enable);
	}
}

static void plic_irq_enable(struct irq_data *d)
{
	unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d),
					   cpu_online_mask);
	if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
		return;
	plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1);
}

static void plic_irq_disable(struct irq_data *d)
{
	plic_irq_toggle(cpu_possible_mask, d->hwirq, 0);
}

#ifdef CONFIG_SMP
static int plic_set_affinity(struct irq_data *d,
			     const struct cpumask *mask_val, bool force)
{
	unsigned int cpu;

	if (force)
		cpu = cpumask_first(mask_val);
	else
		cpu = cpumask_any_and(mask_val, cpu_online_mask);

	if (cpu >= nr_cpu_ids)
		return -EINVAL;

	if (!irqd_irq_disabled(d)) {
		plic_irq_toggle(cpu_possible_mask, d->hwirq, 0);
		plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1);
	}

	irq_data_update_effective_affinity(d, cpumask_of(cpu));

	return IRQ_SET_MASK_OK_DONE;
}
#endif

static struct irq_chip plic_chip = {
	.name		= "SiFive PLIC",
	/*
	 * There is no need to mask/unmask PLIC interrupts.  They are "masked"
	 * by reading claim and "unmasked" when writing it back.
	 */
	.irq_enable	= plic_irq_enable,
	.irq_disable	= plic_irq_disable,
#ifdef CONFIG_SMP
	.irq_set_affinity = plic_set_affinity,
#endif
};

static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq,
			      irq_hw_number_t hwirq)
{
	irq_set_chip_and_handler(irq, &plic_chip, handle_simple_irq);
	irq_set_chip_data(irq, NULL);
	irq_set_noprobe(irq);
	return 0;
}

static const struct irq_domain_ops plic_irqdomain_ops = {
	.map		= plic_irqdomain_map,
	.xlate		= irq_domain_xlate_onecell,
};

static struct irq_domain *plic_irqdomain;

/*
 * Handling an interrupt is a two-step process: first you claim the interrupt
 * by reading the claim register, then you complete the interrupt by writing
 * 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)
{
	struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
	void __iomem *claim = handler->hart_base + CONTEXT_CLAIM;
	irq_hw_number_t hwirq;

	WARN_ON_ONCE(!handler->present);

	csr_clear(sie, SIE_SEIE);
	while ((hwirq = readl(claim))) {
		int irq = irq_find_mapping(plic_irqdomain, hwirq);

		if (unlikely(irq <= 0))
			pr_warn_ratelimited("can't find mapping for hwirq %lu\n",
					hwirq);
		else
			generic_handle_irq(irq);
		writel(hwirq, claim);
	}
	csr_set(sie, SIE_SEIE);
}

/*
 * Walk up the DT tree until we find an active RISC-V core (HART) node and
 * extract the cpuid from it.
 */
static int plic_find_hart_id(struct device_node *node)
{
	for (; node; node = node->parent) {
		if (of_device_is_compatible(node, "riscv"))
			return riscv_of_processor_hartid(node);
	}

	return -1;
}

static int __init plic_init(struct device_node *node,
		struct device_node *parent)
{
	int error = 0, nr_contexts, nr_handlers = 0, i;
	u32 nr_irqs;

	if (plic_regs) {
		pr_warn("PLIC already present.\n");
		return -ENXIO;
	}

	plic_regs = of_iomap(node, 0);
	if (WARN_ON(!plic_regs))
		return -EIO;

	error = -EINVAL;
	of_property_read_u32(node, "riscv,ndev", &nr_irqs);
	if (WARN_ON(!nr_irqs))
		goto out_iounmap;

	nr_contexts = of_irq_count(node);
	if (WARN_ON(!nr_contexts))
		goto out_iounmap;
	if (WARN_ON(nr_contexts < num_possible_cpus()))
		goto out_iounmap;

	error = -ENOMEM;
	plic_irqdomain = irq_domain_add_linear(node, nr_irqs + 1,
			&plic_irqdomain_ops, NULL);
	if (WARN_ON(!plic_irqdomain))
		goto out_iounmap;

	for (i = 0; i < nr_contexts; i++) {
		struct of_phandle_args parent;
		struct plic_handler *handler;
		irq_hw_number_t hwirq;
		int cpu, hartid;

		if (of_irq_parse_one(node, i, &parent)) {
			pr_err("failed to parse parent for context %d.\n", i);
			continue;
		}

		/* skip context holes */
		if (parent.args[0] == -1)
			continue;

		hartid = plic_find_hart_id(parent.np);
		if (hartid < 0) {
			pr_warn("failed to parse hart ID for context %d.\n", i);
			continue;
		}

		cpu = riscv_hartid_to_cpuid(hartid);
		if (cpu < 0) {
			pr_warn("Invalid cpuid for context %d\n", i);
			continue;
		}

		handler = per_cpu_ptr(&plic_handlers, cpu);
		if (handler->present) {
			pr_warn("handler already present for context %d.\n", i);
			continue;
		}

		handler->present = true;
		handler->hart_base =
			plic_regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
		raw_spin_lock_init(&handler->enable_lock);
		handler->enable_base =
			plic_regs + ENABLE_BASE + i * ENABLE_PER_HART;

		/* priority must be > threshold to trigger an interrupt */
		writel(0, handler->hart_base + CONTEXT_THRESHOLD);
		for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
			plic_toggle(handler, hwirq, 0);
		nr_handlers++;
	}

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

out_iounmap:
	iounmap(plic_regs);
	return error;
}

IRQCHIP_DECLARE(sifive_plic, "sifive,plic-1.0.0", plic_init);
IRQCHIP_DECLARE(riscv_plic0, "riscv,plic0", plic_init); /* for legacy systems */