1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 2017 SiFive
4 * Copyright (C) 2018 Christoph Hellwig
6 #define pr_fmt(fmt) "plic: " fmt
7 #include <linux/interrupt.h>
10 #include <linux/irqchip.h>
11 #include <linux/irqdomain.h>
12 #include <linux/module.h>
14 #include <linux/of_address.h>
15 #include <linux/of_irq.h>
16 #include <linux/platform_device.h>
17 #include <linux/spinlock.h>
21 * This driver implements a version of the RISC-V PLIC with the actual layout
22 * specified in chapter 8 of the SiFive U5 Coreplex Series Manual:
24 * https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf
26 * The largest number supported by devices marked as 'sifive,plic-1.0.0', is
27 * 1024, of which device 0 is defined as non-existent by the RISC-V Privileged
31 #define MAX_DEVICES 1024
32 #define MAX_CONTEXTS 15872
35 * Each interrupt source has a priority register associated with it.
36 * We always hardwire it to one in Linux.
38 #define PRIORITY_BASE 0
39 #define PRIORITY_PER_ID 4
42 * Each hart context has a vector of interrupt enable bits associated with it.
43 * There's one bit for each interrupt source.
45 #define ENABLE_BASE 0x2000
46 #define ENABLE_PER_HART 0x80
49 * Each hart context has a set of control registers associated with it. Right
50 * now there's only two: a source priority threshold over which the hart will
51 * take an interrupt, and a register to claim interrupts.
53 #define CONTEXT_BASE 0x200000
54 #define CONTEXT_PER_HART 0x1000
55 #define CONTEXT_THRESHOLD 0x00
56 #define CONTEXT_CLAIM 0x04
58 static void __iomem *plic_regs;
64 static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
66 static inline void __iomem *plic_hart_offset(int ctxid)
68 return plic_regs + CONTEXT_BASE + ctxid * CONTEXT_PER_HART;
71 static inline u32 __iomem *plic_enable_base(int ctxid)
73 return plic_regs + ENABLE_BASE + ctxid * ENABLE_PER_HART;
77 * Protect mask operations on the registers given that we can't assume that
78 * atomic memory operations work on them.
80 static DEFINE_RAW_SPINLOCK(plic_toggle_lock);
82 static inline void plic_toggle(int ctxid, int hwirq, int enable)
84 u32 __iomem *reg = plic_enable_base(ctxid) + (hwirq / 32);
85 u32 hwirq_mask = 1 << (hwirq % 32);
87 raw_spin_lock(&plic_toggle_lock);
89 writel(readl(reg) | hwirq_mask, reg);
91 writel(readl(reg) & ~hwirq_mask, reg);
92 raw_spin_unlock(&plic_toggle_lock);
95 static inline void plic_irq_toggle(struct irq_data *d, int enable)
99 writel(enable, plic_regs + PRIORITY_BASE + d->hwirq * PRIORITY_PER_ID);
100 for_each_cpu(cpu, irq_data_get_affinity_mask(d)) {
101 struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);
103 if (handler->present)
104 plic_toggle(handler->ctxid, d->hwirq, enable);
108 static void plic_irq_enable(struct irq_data *d)
110 plic_irq_toggle(d, 1);
113 static void plic_irq_disable(struct irq_data *d)
115 plic_irq_toggle(d, 0);
118 static struct irq_chip plic_chip = {
119 .name = "SiFive PLIC",
121 * There is no need to mask/unmask PLIC interrupts. They are "masked"
122 * by reading claim and "unmasked" when writing it back.
124 .irq_enable = plic_irq_enable,
125 .irq_disable = plic_irq_disable,
128 static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq,
129 irq_hw_number_t hwirq)
131 irq_set_chip_and_handler(irq, &plic_chip, handle_simple_irq);
132 irq_set_chip_data(irq, NULL);
133 irq_set_noprobe(irq);
137 static const struct irq_domain_ops plic_irqdomain_ops = {
138 .map = plic_irqdomain_map,
139 .xlate = irq_domain_xlate_onecell,
142 static struct irq_domain *plic_irqdomain;
145 * Handling an interrupt is a two-step process: first you claim the interrupt
146 * by reading the claim register, then you complete the interrupt by writing
147 * that source ID back to the same claim register. This automatically enables
148 * and disables the interrupt, so there's nothing else to do.
150 static void plic_handle_irq(struct pt_regs *regs)
152 struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
153 void __iomem *claim = plic_hart_offset(handler->ctxid) + CONTEXT_CLAIM;
154 irq_hw_number_t hwirq;
156 WARN_ON_ONCE(!handler->present);
158 csr_clear(sie, SIE_SEIE);
159 while ((hwirq = readl(claim))) {
160 int irq = irq_find_mapping(plic_irqdomain, hwirq);
162 if (unlikely(irq <= 0))
163 pr_warn_ratelimited("can't find mapping for hwirq %lu\n",
166 generic_handle_irq(irq);
167 writel(hwirq, claim);
169 csr_set(sie, SIE_SEIE);
173 * Walk up the DT tree until we find an active RISC-V core (HART) node and
174 * extract the cpuid from it.
176 static int plic_find_hart_id(struct device_node *node)
178 for (; node; node = node->parent) {
179 if (of_device_is_compatible(node, "riscv"))
180 return riscv_of_processor_hartid(node);
186 static int __init plic_init(struct device_node *node,
187 struct device_node *parent)
189 int error = 0, nr_handlers, nr_mapped = 0, i;
193 pr_warn("PLIC already present.\n");
197 plic_regs = of_iomap(node, 0);
198 if (WARN_ON(!plic_regs))
202 of_property_read_u32(node, "riscv,ndev", &nr_irqs);
203 if (WARN_ON(!nr_irqs))
206 nr_handlers = of_irq_count(node);
207 if (WARN_ON(!nr_handlers))
209 if (WARN_ON(nr_handlers < num_possible_cpus()))
213 plic_irqdomain = irq_domain_add_linear(node, nr_irqs + 1,
214 &plic_irqdomain_ops, NULL);
215 if (WARN_ON(!plic_irqdomain))
218 for (i = 0; i < nr_handlers; i++) {
219 struct of_phandle_args parent;
220 struct plic_handler *handler;
221 irq_hw_number_t hwirq;
224 if (of_irq_parse_one(node, i, &parent)) {
225 pr_err("failed to parse parent for context %d.\n", i);
229 /* skip context holes */
230 if (parent.args[0] == -1)
233 hartid = plic_find_hart_id(parent.np);
235 pr_warn("failed to parse hart ID for context %d.\n", i);
239 cpu = riscv_hartid_to_cpuid(hartid);
240 handler = per_cpu_ptr(&plic_handlers, cpu);
241 handler->present = true;
244 /* priority must be > threshold to trigger an interrupt */
245 writel(0, plic_hart_offset(i) + CONTEXT_THRESHOLD);
246 for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
247 plic_toggle(i, hwirq, 0);
251 pr_info("mapped %d interrupts to %d (out of %d) handlers.\n",
252 nr_irqs, nr_mapped, nr_handlers);
253 set_handle_irq(plic_handle_irq);
261 IRQCHIP_DECLARE(sifive_plic, "sifive,plic-1.0.0", plic_init);
262 IRQCHIP_DECLARE(riscv_plic0, "riscv,plic0", plic_init); /* for legacy systems */