arch/arm/kernel/fiq.c

   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         ldmea   fp, {fp, sp, pc}"
 105         : "=&r" (tmp)
 106         : "r" (&regs->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         ldmea   fp, {fp, sp, pc}"
 123         : "=&r" (tmp)
 124         : "r" (&regs->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 }