sbi-ipi.c

 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
16DEFINE_STATIC_KEY_FALSE(riscv_sbi_for_rfence);
17EXPORT_SYMBOL_GPL(riscv_sbi_for_rfence);
18
19static int sbi_ipi_virq;
20
21static 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
33static 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
39void __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}