1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Multiplex several IPIs over a single HW IPI.
4 *
5 * Copyright (c) 2022 Ventana Micro Systems Inc.
6 */
7
8 #define pr_fmt(fmt) "riscv: " fmt
9 #include <linux/cpu.h>
10 #include <linux/init.h>
11 #include <linux/irq.h>
12 #include <linux/irqchip/chained_irq.h>
13 #include <linux/irqdomain.h>
14 #include <asm/sbi.h>
15
16 DEFINE_STATIC_KEY_FALSE(riscv_sbi_for_rfence);
17 EXPORT_SYMBOL_GPL(riscv_sbi_for_rfence);
18
19 static int sbi_ipi_virq;
20
21 static void sbi_ipi_handle(struct irq_desc *desc)
22 {
23 struct irq_chip *chip = irq_desc_get_chip(desc);
24
25 chained_irq_enter(chip, desc);
26
27 csr_clear(CSR_IP, IE_SIE);
28 ipi_mux_process();
29
30 chained_irq_exit(chip, desc);
31 }
32
33 static int sbi_ipi_starting_cpu(unsigned int cpu)
34 {
35 enable_percpu_irq(sbi_ipi_virq, irq_get_trigger_type(sbi_ipi_virq));
36 return 0;
37 }
38
39 void __init sbi_ipi_init(void)
40 {
41 int virq;
42 struct irq_domain *domain;
43
44 if (riscv_ipi_have_virq_range())
45 return;
46
47 domain = irq_find_matching_fwnode(riscv_get_intc_hwnode(),
48 DOMAIN_BUS_ANY);
49 if (!domain) {
50 pr_err("unable to find INTC IRQ domain\n");
51 return;
52 }
53
54 sbi_ipi_virq = irq_create_mapping(domain, RV_IRQ_SOFT);
55 if (!sbi_ipi_virq) {
56 pr_err("unable to create INTC IRQ mapping\n");
57 return;
58 }
59
60 virq = ipi_mux_create(BITS_PER_BYTE, sbi_send_ipi);
61 if (virq <= 0) {
62 pr_err("unable to create muxed IPIs\n");
63 irq_dispose_mapping(sbi_ipi_virq);
64 return;
65 }
66
67 irq_set_chained_handler(sbi_ipi_virq, sbi_ipi_handle);
68
69 /*
70 * Don't disable IPI when CPU goes offline because
71 * the masking/unmasking of virtual IPIs is done
72 * via generic IPI-Mux
73 */
74 cpuhp_setup_state(CPUHP_AP_IRQ_RISCV_SBI_IPI_STARTING,
75 "irqchip/sbi-ipi:starting",
76 sbi_ipi_starting_cpu, NULL);
77
78 riscv_ipi_set_virq_range(virq, BITS_PER_BYTE);
79 pr_info("providing IPIs using SBI IPI extension\n");
80
81 /*
82 * Use the SBI remote fence extension to avoid
83 * the extra context switch needed to handle IPIs.
84 */
85 static_branch_enable(&riscv_sbi_for_rfence);
86 }
87
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