arch/powerpc/kernel/dbell.c

   1 /*
   2  * Author: Kumar Gala <galak@kernel.crashing.org>
   3  *
   4  * Copyright 2009 Freescale Semiconductor Inc.
   5  *
   6  * This program is free software; you can redistribute  it and/or modify it
   7  * under  the terms of  the GNU General  Public License as published by the
   8  * Free Software Foundation;  either version 2 of the  License, or (at your
   9  * option) any later version.
  10  */
  11
  12 #include <linux/stddef.h>
  13 #include <linux/kernel.h>
  14 #include <linux/smp.h>
  15 #include <linux/threads.h>
  16 #include <linux/hardirq.h>
  17
  18 #include <asm/dbell.h>
  19 #include <asm/irq_regs.h>
  20 #include <asm/kvm_ppc.h>
  21
  22 #ifdef CONFIG_SMP
  23
  24 /*
  25  * Doorbells must only be used if CPU_FTR_DBELL is available.
  26  * msgsnd is used in HV, and msgsndp is used in !HV.
  27  *
  28  * These should be used by platform code that is aware of restrictions.
  29  * Other arch code should use ->cause_ipi.
  30  *
  31  * doorbell_global_ipi() sends a dbell to any target CPU.
  32  * Must be used only by architectures that address msgsnd target
  33  * by PIR/get_hard_smp_processor_id.
  34  */
  35 void doorbell_global_ipi(int cpu)
  36 {
  37         u32 tag = get_hard_smp_processor_id(cpu);
  38
  39         kvmppc_set_host_ipi(cpu, 1);
  40         /* Order previous accesses vs. msgsnd, which is treated as a store */
  41         ppc_msgsnd_sync();
  42         ppc_msgsnd(PPC_DBELL_MSGTYPE, 0, tag);
  43 }
  44
  45 /*
  46  * doorbell_core_ipi() sends a dbell to a target CPU in the same core.
  47  * Must be used only by architectures that address msgsnd target
  48  * by TIR/cpu_thread_in_core.
  49  */
  50 void doorbell_core_ipi(int cpu)
  51 {
  52         u32 tag = cpu_thread_in_core(cpu);
  53
  54         kvmppc_set_host_ipi(cpu, 1);
  55         /* Order previous accesses vs. msgsnd, which is treated as a store */
  56         ppc_msgsnd_sync();
  57         ppc_msgsnd(PPC_DBELL_MSGTYPE, 0, tag);
  58 }
  59
  60 /*
  61  * Attempt to cause a core doorbell if destination is on the same core.
  62  * Returns 1 on success, 0 on failure.
  63  */
  64 int doorbell_try_core_ipi(int cpu)
  65 {
  66         int this_cpu = get_cpu();
  67         int ret = 0;
  68
  69         if (cpumask_test_cpu(cpu, cpu_sibling_mask(this_cpu))) {
  70                 doorbell_core_ipi(cpu);
  71                 ret = 1;
  72         }
  73
  74         put_cpu();
  75
  76         return ret;
  77 }
  78
  79 void doorbell_exception(struct pt_regs *regs)
  80 {
  81         struct pt_regs *old_regs = set_irq_regs(regs);
  82
  83         irq_enter();
  84
  85         ppc_msgsync();
  86
  87         may_hard_irq_enable();
  88
  89         kvmppc_set_host_ipi(smp_processor_id(), 0);
  90         __this_cpu_inc(irq_stat.doorbell_irqs);
  91
  92         smp_ipi_demux_relaxed(); /* already performed the barrier */
  93
  94         irq_exit();
  95         set_irq_regs(old_regs);
  96 }
  97 #else /* CONFIG_SMP */
  98 void doorbell_exception(struct pt_regs *regs)
  99 {
 100         printk(KERN_WARNING "Received doorbell on non-smp system\n");
 101 }
 102 #endif /* CONFIG_SMP */
 103