1 /* 2 * linux/arch/arm/kernel/fiq.c 3 * 4 * Copyright (C) 1998 Russell King 5 * Copyright (C) 1998, 1999 Phil Blundell 6 * 7 * FIQ support written by Philip Blundell <philb@gnu.org>, 1998. 8 * 9 * FIQ support re-written by Russell King to be more generic 10 * 11 * We now properly support a method by which the FIQ handlers can 12 * be stacked onto the vector. We still do not support sharing 13 * the FIQ vector itself. 14 * 15 * Operation is as follows: 16 * 1. Owner A claims FIQ: 17 * - default_fiq relinquishes control. 18 * 2. Owner A: 19 * - inserts code. 20 * - sets any registers, 21 * - enables FIQ. 22 * 3. Owner B claims FIQ: 23 * - if owner A has a relinquish function. 24 * - disable FIQs. 25 * - saves any registers. 26 * - returns zero. 27 * 4. Owner B: 28 * - inserts code. 29 * - sets any registers, 30 * - enables FIQ. 31 * 5. Owner B releases FIQ: 32 * - Owner A is asked to reacquire FIQ: 33 * - inserts code. 34 * - restores saved registers. 35 * - enables FIQ. 36 * 6. Goto 3 37 */ 38 #include <linux/module.h> 39 #include <linux/kernel.h> 40 #include <linux/init.h> 41 #include <linux/interrupt.h> 42 #include <linux/seq_file.h> 43 44 #include <asm/cacheflush.h> 45 #include <asm/fiq.h> 46 #include <asm/irq.h> 47 #include <asm/system.h> 48 #include <asm/uaccess.h> 49 50 static unsigned long no_fiq_insn; 51 52 /* Default reacquire function 53 * - we always relinquish FIQ control 54 * - we always reacquire FIQ control 55 */ 56 static int fiq_def_op(void *ref, int relinquish) 57 { 58 if (!relinquish) 59 set_fiq_handler(&no_fiq_insn, sizeof(no_fiq_insn)); 60 61 return 0; 62 } 63 64 static struct fiq_handler default_owner = { 65 .name = "default", 66 .fiq_op = fiq_def_op, 67 }; 68 69 static struct fiq_handler *current_fiq = &default_owner; 70 71 int show_fiq_list(struct seq_file *p, void *v) 72 { 73 if (current_fiq != &default_owner) 74 seq_printf(p, "FIQ: %s\n", current_fiq->name); 75 76 return 0; 77 } 78 79 void set_fiq_handler(void *start, unsigned int length) 80 { 81 memcpy((void *)0xffff001c, start, length); 82 flush_icache_range(0xffff001c, 0xffff001c + length); 83 if (!vectors_high()) 84 flush_icache_range(0x1c, 0x1c + length); 85 } 86 87 /* 88 * Taking an interrupt in FIQ mode is death, so both these functions 89 * disable irqs for the duration. Note - these functions are almost 90 * entirely coded in assembly. 91 */ 92 void __attribute__((naked)) set_fiq_regs(struct pt_regs *regs) 93 { 94 register unsigned long tmp; 95 asm volatile ( 96 "mov ip, sp\n\ 97 stmfd sp!, {fp, ip, lr, pc}\n\ 98 sub fp, ip, #4\n\ 99 mrs %0, cpsr\n\ 100 msr cpsr_c, %2 @ select FIQ mode\n\ 101 mov r0, r0\n\ 102 ldmia %1, {r8 - r14}\n\ 103 msr cpsr_c, %0 @ return to SVC mode\n\ 104 mov r0, r0\n\ 105 ldmfd sp, {fp, sp, pc}" 106 : "=&r" (tmp) 107 : "r" (®s->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE)); 108 } 109 110 void __attribute__((naked)) get_fiq_regs(struct pt_regs *regs) 111 { 112 register unsigned long tmp; 113 asm volatile ( 114 "mov ip, sp\n\ 115 stmfd sp!, {fp, ip, lr, pc}\n\ 116 sub fp, ip, #4\n\ 117 mrs %0, cpsr\n\ 118 msr cpsr_c, %2 @ select FIQ mode\n\ 119 mov r0, r0\n\ 120 stmia %1, {r8 - r14}\n\ 121 msr cpsr_c, %0 @ return to SVC mode\n\ 122 mov r0, r0\n\ 123 ldmfd sp, {fp, sp, pc}" 124 : "=&r" (tmp) 125 : "r" (®s->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE)); 126 } 127 128 int claim_fiq(struct fiq_handler *f) 129 { 130 int ret = 0; 131 132 if (current_fiq) { 133 ret = -EBUSY; 134 135 if (current_fiq->fiq_op != NULL) 136 ret = current_fiq->fiq_op(current_fiq->dev_id, 1); 137 } 138 139 if (!ret) { 140 f->next = current_fiq; 141 current_fiq = f; 142 } 143 144 return ret; 145 } 146 147 void release_fiq(struct fiq_handler *f) 148 { 149 if (current_fiq != f) { 150 printk(KERN_ERR "%s FIQ trying to release %s FIQ\n", 151 f->name, current_fiq->name); 152 dump_stack(); 153 return; 154 } 155 156 do 157 current_fiq = current_fiq->next; 158 while (current_fiq->fiq_op(current_fiq->dev_id, 0)); 159 } 160 161 void enable_fiq(int fiq) 162 { 163 enable_irq(fiq + FIQ_START); 164 } 165 166 void disable_fiq(int fiq) 167 { 168 disable_irq(fiq + FIQ_START); 169 } 170 171 EXPORT_SYMBOL(set_fiq_handler); 172 EXPORT_SYMBOL(set_fiq_regs); 173 EXPORT_SYMBOL(get_fiq_regs); 174 EXPORT_SYMBOL(claim_fiq); 175 EXPORT_SYMBOL(release_fiq); 176 EXPORT_SYMBOL(enable_fiq); 177 EXPORT_SYMBOL(disable_fiq); 178 179 void __init init_FIQ(void) 180 { 181 no_fiq_insn = *(unsigned long *)0xffff001c; 182 } 183