arch/riscv/kernel/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
  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 }