kernel/irq/ipi.c

   1 /*
   2  * linux/kernel/irq/ipi.c
   3  *
   4  * Copyright (C) 2015 Imagination Technologies Ltd
   5  * Author: Qais Yousef <qais.yousef@imgtec.com>
   6  *
   7  * This file contains driver APIs to the IPI subsystem.
   8  */
   9
  10 #define pr_fmt(fmt) "genirq/ipi: " fmt
  11
  12 #include <linux/irqdomain.h>
  13 #include <linux/irq.h>
  14
  15 /**
  16  * irq_reserve_ipi() - Setup an IPI to destination cpumask
  17  * @domain:     IPI domain
  18  * @dest:       cpumask of cpus which can receive the IPI
  19  *
  20  * Allocate a virq that can be used to send IPI to any CPU in dest mask.
  21  *
  22  * On success it'll return linux irq number and 0 on failure
  23  */
  24 unsigned int irq_reserve_ipi(struct irq_domain *domain,
  25                              const struct cpumask *dest)
  26 {
  27         unsigned int nr_irqs, offset;
  28         struct irq_data *data;
  29         int virq, i;
  30
  31         if (!domain ||!irq_domain_is_ipi(domain)) {
  32                 pr_warn("Reservation on a non IPI domain\n");
  33                 return 0;
  34         }
  35
  36         if (!cpumask_subset(dest, cpu_possible_mask)) {
  37                 pr_warn("Reservation is not in possible_cpu_mask\n");
  38                 return 0;
  39         }
  40
  41         nr_irqs = cpumask_weight(dest);
  42         if (!nr_irqs) {
  43                 pr_warn("Reservation for empty destination mask\n");
  44                 return 0;
  45         }
  46
  47         if (irq_domain_is_ipi_single(domain)) {
  48                 /*
  49                  * If the underlying implementation uses a single HW irq on
  50                  * all cpus then we only need a single Linux irq number for
  51                  * it. We have no restrictions vs. the destination mask. The
  52                  * underlying implementation can deal with holes nicely.
  53                  */
  54                 nr_irqs = 1;
  55                 offset = 0;
  56         } else {
  57                 unsigned int next;
  58
  59                 /*
  60                  * The IPI requires a seperate HW irq on each CPU. We require
  61                  * that the destination mask is consecutive. If an
  62                  * implementation needs to support holes, it can reserve
  63                  * several IPI ranges.
  64                  */
  65                 offset = cpumask_first(dest);
  66                 /*
  67                  * Find a hole and if found look for another set bit after the
  68                  * hole. For now we don't support this scenario.
  69                  */
  70                 next = cpumask_next_zero(offset, dest);
  71                 if (next < nr_cpu_ids)
  72                         next = cpumask_next(next, dest);
  73                 if (next < nr_cpu_ids) {
  74                         pr_warn("Destination mask has holes\n");
  75                         return 0;
  76                 }
  77         }
  78
  79         virq = irq_domain_alloc_descs(-1, nr_irqs, 0, NUMA_NO_NODE);
  80         if (virq <= 0) {
  81                 pr_warn("Can't reserve IPI, failed to alloc descs\n");
  82                 return 0;
  83         }
  84
  85         virq = __irq_domain_alloc_irqs(domain, virq, nr_irqs, NUMA_NO_NODE,
  86                                        (void *) dest, true);
  87
  88         if (virq <= 0) {
  89                 pr_warn("Can't reserve IPI, failed to alloc hw irqs\n");
  90                 goto free_descs;
  91         }
  92
  93         for (i = 0; i < nr_irqs; i++) {
  94                 data = irq_get_irq_data(virq + i);
  95                 cpumask_copy(data->common->affinity, dest);
  96                 data->common->ipi_offset = offset;
  97         }
  98         return virq;
  99
 100 free_descs:
 101         irq_free_descs(virq, nr_irqs);
 102         return 0;
 103 }
 104
 105 /**
 106  * irq_destroy_ipi() - unreserve an IPI that was previously allocated
 107  * @irq:        linux irq number to be destroyed
 108  *
 109  * Return the IPIs allocated with irq_reserve_ipi() to the system destroying
 110  * all virqs associated with them.
 111  */
 112 void irq_destroy_ipi(unsigned int irq)
 113 {
 114         struct irq_data *data = irq_get_irq_data(irq);
 115         struct cpumask *ipimask = data ? irq_data_get_affinity_mask(data) : NULL;
 116         struct irq_domain *domain;
 117         unsigned int nr_irqs;
 118
 119         if (!irq || !data || !ipimask)
 120                 return;
 121
 122         domain = data->domain;
 123         if (WARN_ON(domain == NULL))
 124                 return;
 125
 126         if (!irq_domain_is_ipi(domain)) {
 127                 pr_warn("Trying to destroy a non IPI domain!\n");
 128                 return;
 129         }
 130
 131         if (irq_domain_is_ipi_per_cpu(domain))
 132                 nr_irqs = cpumask_weight(ipimask);
 133         else
 134                 nr_irqs = 1;
 135
 136         irq_domain_free_irqs(irq, nr_irqs);
 137 }