1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright (C) 2012 Regents of the University of California
4  * Copyright (C) 2017-2018 SiFive
5  * Copyright (C) 2020 Western Digital Corporation or its affiliates.
6  */
7 
8 #define pr_fmt(fmt) "riscv-intc: " fmt
9 #include <linux/atomic.h>
10 #include <linux/bits.h>
11 #include <linux/cpu.h>
12 #include <linux/irq.h>
13 #include <linux/irqchip.h>
14 #include <linux/irqdomain.h>
15 #include <linux/interrupt.h>
16 #include <linux/module.h>
17 #include <linux/of.h>
18 #include <linux/smp.h>
19 
20 static struct irq_domain *intc_domain;
21 
22 static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
23 {
24 	unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;
25 
26 	if (unlikely(cause >= BITS_PER_LONG))
27 		panic("unexpected interrupt cause");
28 
29 	switch (cause) {
30 #ifdef CONFIG_SMP
31 	case RV_IRQ_SOFT:
32 		/*
33 		 * We only use software interrupts to pass IPIs, so if a
34 		 * non-SMP system gets one, then we don't know what to do.
35 		 */
36 		handle_IPI(regs);
37 		break;
38 #endif
39 	default:
40 		generic_handle_domain_irq(intc_domain, cause);
41 		break;
42 	}
43 }
44 
45 /*
46  * On RISC-V systems local interrupts are masked or unmasked by writing
47  * the SIE (Supervisor Interrupt Enable) CSR.  As CSRs can only be written
48  * on the local hart, these functions can only be called on the hart that
49  * corresponds to the IRQ chip.
50  */
51 
52 static void riscv_intc_irq_mask(struct irq_data *d)
53 {
54 	csr_clear(CSR_IE, BIT(d->hwirq));
55 }
56 
57 static void riscv_intc_irq_unmask(struct irq_data *d)
58 {
59 	csr_set(CSR_IE, BIT(d->hwirq));
60 }
61 
62 static int riscv_intc_cpu_starting(unsigned int cpu)
63 {
64 	csr_set(CSR_IE, BIT(RV_IRQ_SOFT));
65 	return 0;
66 }
67 
68 static int riscv_intc_cpu_dying(unsigned int cpu)
69 {
70 	csr_clear(CSR_IE, BIT(RV_IRQ_SOFT));
71 	return 0;
72 }
73 
74 static struct irq_chip riscv_intc_chip = {
75 	.name = "RISC-V INTC",
76 	.irq_mask = riscv_intc_irq_mask,
77 	.irq_unmask = riscv_intc_irq_unmask,
78 };
79 
80 static int riscv_intc_domain_map(struct irq_domain *d, unsigned int irq,
81 				 irq_hw_number_t hwirq)
82 {
83 	irq_set_percpu_devid(irq);
84 	irq_domain_set_info(d, irq, hwirq, &riscv_intc_chip, d->host_data,
85 			    handle_percpu_devid_irq, NULL, NULL);
86 
87 	return 0;
88 }
89 
90 static const struct irq_domain_ops riscv_intc_domain_ops = {
91 	.map	= riscv_intc_domain_map,
92 	.xlate	= irq_domain_xlate_onecell,
93 };
94 
95 static int __init riscv_intc_init(struct device_node *node,
96 				  struct device_node *parent)
97 {
98 	int rc;
99 	unsigned long hartid;
100 
101 	rc = riscv_of_parent_hartid(node, &hartid);
102 	if (rc < 0) {
103 		pr_warn("unable to find hart id for %pOF\n", node);
104 		return 0;
105 	}
106 
107 	/*
108 	 * The DT will have one INTC DT node under each CPU (or HART)
109 	 * DT node so riscv_intc_init() function will be called once
110 	 * for each INTC DT node. We only need to do INTC initialization
111 	 * for the INTC DT node belonging to boot CPU (or boot HART).
112 	 */
113 	if (riscv_hartid_to_cpuid(hartid) != smp_processor_id())
114 		return 0;
115 
116 	intc_domain = irq_domain_add_linear(node, BITS_PER_LONG,
117 					    &riscv_intc_domain_ops, NULL);
118 	if (!intc_domain) {
119 		pr_err("unable to add IRQ domain\n");
120 		return -ENXIO;
121 	}
122 
123 	rc = set_handle_irq(&riscv_intc_irq);
124 	if (rc) {
125 		pr_err("failed to set irq handler\n");
126 		return rc;
127 	}
128 
129 	cpuhp_setup_state(CPUHP_AP_IRQ_RISCV_STARTING,
130 			  "irqchip/riscv/intc:starting",
131 			  riscv_intc_cpu_starting,
132 			  riscv_intc_cpu_dying);
133 
134 	pr_info("%d local interrupts mapped\n", BITS_PER_LONG);
135 
136 	return 0;
137 }
138 
139 IRQCHIP_DECLARE(riscv, "riscv,cpu-intc", riscv_intc_init);
140