arch/riscv/kernel/smp.c

   1 /*
   2  * SMP initialisation and IPI support
   3  * Based on arch/arm64/kernel/smp.c
   4  *
   5  * Copyright (C) 2012 ARM Ltd.
   6  * Copyright (C) 2015 Regents of the University of California
   7  * Copyright (C) 2017 SiFive
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20  */
  21
  22 #include <linux/interrupt.h>
  23 #include <linux/smp.h>
  24 #include <linux/sched.h>
  25
  26 #include <asm/sbi.h>
  27 #include <asm/tlbflush.h>
  28 #include <asm/cacheflush.h>
  29
  30 /* A collection of single bit ipi messages.  */
  31 static struct {
  32         unsigned long bits ____cacheline_aligned;
  33 } ipi_data[NR_CPUS] __cacheline_aligned;
  34
  35 enum ipi_message_type {
  36         IPI_RESCHEDULE,
  37         IPI_CALL_FUNC,
  38         IPI_MAX
  39 };
  40
  41 irqreturn_t handle_ipi(void)
  42 {
  43         unsigned long *pending_ipis = &ipi_data[smp_processor_id()].bits;
  44
  45         /* Clear pending IPI */
  46         csr_clear(sip, SIE_SSIE);
  47
  48         while (true) {
  49                 unsigned long ops;
  50
  51                 /* Order bit clearing and data access. */
  52                 mb();
  53
  54                 ops = xchg(pending_ipis, 0);
  55                 if (ops == 0)
  56                         return IRQ_HANDLED;
  57
  58                 if (ops & (1 << IPI_RESCHEDULE))
  59                         scheduler_ipi();
  60
  61                 if (ops & (1 << IPI_CALL_FUNC))
  62                         generic_smp_call_function_interrupt();
  63
  64                 BUG_ON((ops >> IPI_MAX) != 0);
  65
  66                 /* Order data access and bit testing. */
  67                 mb();
  68         }
  69
  70         return IRQ_HANDLED;
  71 }
  72
  73 static void
  74 send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
  75 {
  76         int i;
  77
  78         mb();
  79         for_each_cpu(i, to_whom)
  80                 set_bit(operation, &ipi_data[i].bits);
  81
  82         mb();
  83         sbi_send_ipi(cpumask_bits(to_whom));
  84 }
  85
  86 void arch_send_call_function_ipi_mask(struct cpumask *mask)
  87 {
  88         send_ipi_message(mask, IPI_CALL_FUNC);
  89 }
  90
  91 void arch_send_call_function_single_ipi(int cpu)
  92 {
  93         send_ipi_message(cpumask_of(cpu), IPI_CALL_FUNC);
  94 }
  95
  96 static void ipi_stop(void *unused)
  97 {
  98         while (1)
  99                 wait_for_interrupt();
 100 }
 101
 102 void smp_send_stop(void)
 103 {
 104         on_each_cpu(ipi_stop, NULL, 1);
 105 }
 106
 107 void smp_send_reschedule(int cpu)
 108 {
 109         send_ipi_message(cpumask_of(cpu), IPI_RESCHEDULE);
 110 }