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/seq_file.h> 42 43 #include <asm/cacheflush.h> 44 #include <asm/fiq.h> 45 #include <asm/irq.h> 46 #include <asm/system.h> 47 #include <asm/uaccess.h> 48 49 static unsigned long no_fiq_insn; 50 51 /* Default reacquire function 52 * - we always relinquish FIQ control 53 * - we always reacquire FIQ control 54 */ 55 static int fiq_def_op(void *ref, int relinquish) 56 { 57 if (!relinquish) 58 set_fiq_handler(&no_fiq_insn, sizeof(no_fiq_insn)); 59 60 return 0; 61 } 62 63 static struct fiq_handler default_owner = { 64 .name = "default", 65 .fiq_op = fiq_def_op, 66 }; 67 68 static struct fiq_handler *current_fiq = &default_owner; 69 70 int show_fiq_list(struct seq_file *p, void *v) 71 { 72 if (current_fiq != &default_owner) 73 seq_printf(p, "FIQ: %s\n", current_fiq->name); 74 75 return 0; 76 } 77 78 void set_fiq_handler(void *start, unsigned int length) 79 { 80 memcpy((void *)0xffff001c, start, length); 81 flush_icache_range(0xffff001c, 0xffff001c + length); 82 if (!vectors_high()) 83 flush_icache_range(0x1c, 0x1c + length); 84 } 85 86 /* 87 * Taking an interrupt in FIQ mode is death, so both these functions 88 * disable irqs for the duration. Note - these functions are almost 89 * entirely coded in assembly. 90 */ 91 void __attribute__((naked)) set_fiq_regs(struct pt_regs *regs) 92 { 93 register unsigned long tmp; 94 asm volatile ( 95 "mov ip, sp\n\ 96 stmfd sp!, {fp, ip, lr, pc}\n\ 97 sub fp, ip, #4\n\ 98 mrs %0, cpsr\n\ 99 msr cpsr_c, %2 @ select FIQ mode\n\ 100 mov r0, r0\n\ 101 ldmia %1, {r8 - r14}\n\ 102 msr cpsr_c, %0 @ return to SVC mode\n\ 103 mov r0, r0\n\ 104 ldmfd sp, {fp, sp, pc}" 105 : "=&r" (tmp) 106 : "r" (®s->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE)); 107 } 108 109 void __attribute__((naked)) get_fiq_regs(struct pt_regs *regs) 110 { 111 register unsigned long tmp; 112 asm volatile ( 113 "mov ip, sp\n\ 114 stmfd sp!, {fp, ip, lr, pc}\n\ 115 sub fp, ip, #4\n\ 116 mrs %0, cpsr\n\ 117 msr cpsr_c, %2 @ select FIQ mode\n\ 118 mov r0, r0\n\ 119 stmia %1, {r8 - r14}\n\ 120 msr cpsr_c, %0 @ return to SVC mode\n\ 121 mov r0, r0\n\ 122 ldmfd sp, {fp, sp, pc}" 123 : "=&r" (tmp) 124 : "r" (®s->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE)); 125 } 126 127 int claim_fiq(struct fiq_handler *f) 128 { 129 int ret = 0; 130 131 if (current_fiq) { 132 ret = -EBUSY; 133 134 if (current_fiq->fiq_op != NULL) 135 ret = current_fiq->fiq_op(current_fiq->dev_id, 1); 136 } 137 138 if (!ret) { 139 f->next = current_fiq; 140 current_fiq = f; 141 } 142 143 return ret; 144 } 145 146 void release_fiq(struct fiq_handler *f) 147 { 148 if (current_fiq != f) { 149 printk(KERN_ERR "%s FIQ trying to release %s FIQ\n", 150 f->name, current_fiq->name); 151 dump_stack(); 152 return; 153 } 154 155 do 156 current_fiq = current_fiq->next; 157 while (current_fiq->fiq_op(current_fiq->dev_id, 0)); 158 } 159 160 void enable_fiq(int fiq) 161 { 162 enable_irq(fiq + FIQ_START); 163 } 164 165 void disable_fiq(int fiq) 166 { 167 disable_irq(fiq + FIQ_START); 168 } 169 170 EXPORT_SYMBOL(set_fiq_handler); 171 EXPORT_SYMBOL(set_fiq_regs); 172 EXPORT_SYMBOL(get_fiq_regs); 173 EXPORT_SYMBOL(claim_fiq); 174 EXPORT_SYMBOL(release_fiq); 175 EXPORT_SYMBOL(enable_fiq); 176 EXPORT_SYMBOL(disable_fiq); 177 178 void __init init_FIQ(void) 179 { 180 no_fiq_insn = *(unsigned long *)0xffff001c; 181 } 182