arch/arm/kernel/fiq.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/arch/arm/kernel/fiq.c
   4  *
   5  *  Copyright (C) 1998 Russell King
   6  *  Copyright (C) 1998, 1999 Phil Blundell
   7  *
   8  *  FIQ support written by Philip Blundell <philb@gnu.org>, 1998.
   9  *
  10  *  FIQ support re-written by Russell King to be more generic
  11  *
  12  * We now properly support a method by which the FIQ handlers can
  13  * be stacked onto the vector.  We still do not support sharing
  14  * the FIQ vector itself.
  15  *
  16  * Operation is as follows:
  17  *  1. Owner A claims FIQ:
  18  *     - default_fiq relinquishes control.
  19  *  2. Owner A:
  20  *     - inserts code.
  21  *     - sets any registers,
  22  *     - enables FIQ.
  23  *  3. Owner B claims FIQ:
  24  *     - if owner A has a relinquish function.
  25  *       - disable FIQs.
  26  *       - saves any registers.
  27  *       - returns zero.
  28  *  4. Owner B:
  29  *     - inserts code.
  30  *     - sets any registers,
  31  *     - enables FIQ.
  32  *  5. Owner B releases FIQ:
  33  *     - Owner A is asked to reacquire FIQ:
  34  *       - inserts code.
  35  *       - restores saved registers.
  36  *       - enables FIQ.
  37  *  6. Goto 3
  38  */
  39 #include <linux/module.h>
  40 #include <linux/kernel.h>
  41 #include <linux/init.h>
  42 #include <linux/interrupt.h>
  43 #include <linux/seq_file.h>
  44
  45 #include <asm/cacheflush.h>
  46 #include <asm/cp15.h>
  47 #include <asm/fiq.h>
  48 #include <asm/irq.h>
  49 #include <asm/traps.h>
  50
  51 #define FIQ_OFFSET ({                                   \
  52                 extern void *vector_fiq_offset;         \
  53                 (unsigned)&vector_fiq_offset;           \
  54         })
  55
  56 static unsigned long dfl_fiq_insn;
  57 static struct pt_regs dfl_fiq_regs;
  58
  59 /* Default reacquire function
  60  * - we always relinquish FIQ control
  61  * - we always reacquire FIQ control
  62  */
  63 static int fiq_def_op(void *ref, int relinquish)
  64 {
  65         if (!relinquish) {
  66                 /* Restore default handler and registers */
  67                 local_fiq_disable();
  68                 set_fiq_regs(&dfl_fiq_regs);
  69                 set_fiq_handler(&dfl_fiq_insn, sizeof(dfl_fiq_insn));
  70                 local_fiq_enable();
  71
  72                 /* FIXME: notify irq controller to standard enable FIQs */
  73         }
  74
  75         return 0;
  76 }
  77
  78 static struct fiq_handler default_owner = {
  79         .name   = "default",
  80         .fiq_op = fiq_def_op,
  81 };
  82
  83 static struct fiq_handler *current_fiq = &default_owner;
  84
  85 int show_fiq_list(struct seq_file *p, int prec)
  86 {
  87         if (current_fiq != &default_owner)
  88                 seq_printf(p, "%*s:              %s\n", prec, "FIQ",
  89                         current_fiq->name);
  90
  91         return 0;
  92 }
  93
  94 void set_fiq_handler(void *start, unsigned int length)
  95 {
  96         void *base = vectors_page;
  97         unsigned offset = FIQ_OFFSET;
  98
  99         memcpy(base + offset, start, length);
 100         if (!cache_is_vipt_nonaliasing())
 101                 flush_icache_range((unsigned long)base + offset,
 102                                    (unsigned long)base + offset + length);
 103         flush_icache_range(0xffff0000 + offset, 0xffff0000 + offset + length);
 104 }
 105
 106 int claim_fiq(struct fiq_handler *f)
 107 {
 108         int ret = 0;
 109
 110         if (current_fiq) {
 111                 ret = -EBUSY;
 112
 113                 if (current_fiq->fiq_op != NULL)
 114                         ret = current_fiq->fiq_op(current_fiq->dev_id, 1);
 115         }
 116
 117         if (!ret) {
 118                 f->next = current_fiq;
 119                 current_fiq = f;
 120         }
 121
 122         return ret;
 123 }
 124
 125 void release_fiq(struct fiq_handler *f)
 126 {
 127         if (current_fiq != f) {
 128                 pr_err("%s FIQ trying to release %s FIQ\n",
 129                        f->name, current_fiq->name);
 130                 dump_stack();
 131                 return;
 132         }
 133
 134         do
 135                 current_fiq = current_fiq->next;
 136         while (current_fiq->fiq_op(current_fiq->dev_id, 0));
 137 }
 138
 139 static int fiq_start;
 140
 141 void enable_fiq(int fiq)
 142 {
 143         enable_irq(fiq + fiq_start);
 144 }
 145
 146 void disable_fiq(int fiq)
 147 {
 148         disable_irq(fiq + fiq_start);
 149 }
 150
 151 EXPORT_SYMBOL(set_fiq_handler);
 152 EXPORT_SYMBOL(__set_fiq_regs);  /* defined in fiqasm.S */
 153 EXPORT_SYMBOL(__get_fiq_regs);  /* defined in fiqasm.S */
 154 EXPORT_SYMBOL(claim_fiq);
 155 EXPORT_SYMBOL(release_fiq);
 156 EXPORT_SYMBOL(enable_fiq);
 157 EXPORT_SYMBOL(disable_fiq);
 158
 159 void __init init_FIQ(int start)
 160 {
 161         unsigned offset = FIQ_OFFSET;
 162         dfl_fiq_insn = *(unsigned long *)(0xffff0000 + offset);
 163         get_fiq_regs(&dfl_fiq_regs);
 164         fiq_start = start;
 165 }