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 } 166