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 #define FIQ_VECTOR (vectors_base() + 0x1c)
  50
  51 static unsigned long no_fiq_insn;
  52
  53 static inline void unprotect_page_0(void)
  54 {
  55         modify_domain(DOMAIN_USER, DOMAIN_MANAGER);
  56 }
  57
  58 static inline void protect_page_0(void)
  59 {
  60         modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
  61 }
  62
  63 /* Default reacquire function
  64  * - we always relinquish FIQ control
  65  * - we always reacquire FIQ control
  66  */
  67 static int fiq_def_op(void *ref, int relinquish)
  68 {
  69         if (!relinquish) {
  70                 unprotect_page_0();
  71                 *(unsigned long *)FIQ_VECTOR = no_fiq_insn;
  72                 protect_page_0();
  73                 flush_icache_range(FIQ_VECTOR, FIQ_VECTOR + 4);
  74         }
  75
  76         return 0;
  77 }
  78
  79 static struct fiq_handler default_owner = {
  80         .name   = "default",
  81         .fiq_op = fiq_def_op,
  82 };
  83
  84 static struct fiq_handler *current_fiq = &default_owner;
  85
  86 int show_fiq_list(struct seq_file *p, void *v)
  87 {
  88         if (current_fiq != &default_owner)
  89                 seq_printf(p, "FIQ:              %s\n", current_fiq->name);
  90
  91         return 0;
  92 }
  93
  94 void set_fiq_handler(void *start, unsigned int length)
  95 {
  96         unprotect_page_0();
  97
  98         memcpy((void *)FIQ_VECTOR, start, length);
  99
 100         protect_page_0();
 101         flush_icache_range(FIQ_VECTOR, FIQ_VECTOR + length);
 102 }
 103
 104 /*
 105  * Taking an interrupt in FIQ mode is death, so both these functions
 106  * disable irqs for the duration.
 107  */
 108 void set_fiq_regs(struct pt_regs *regs)
 109 {
 110         register unsigned long tmp, tmp2;
 111         __asm__ volatile (
 112         "mrs    %0, cpsr\n\
 113         mov     %1, %3\n\
 114         msr     cpsr_c, %1      @ select FIQ mode\n\
 115         mov     r0, r0\n\
 116         ldmia   %2, {r8 - r14}\n\
 117         msr     cpsr_c, %0      @ return to SVC mode\n\
 118         mov     r0, r0"
 119         : "=&r" (tmp), "=&r" (tmp2)
 120         : "r" (&regs->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE)
 121         /* These registers aren't modified by the above code in a way
 122            visible to the compiler, but we mark them as clobbers anyway
 123            so that GCC won't put any of the input or output operands in
 124            them.  */
 125         : "r8", "r9", "r10", "r11", "r12", "r13", "r14");
 126 }
 127
 128 void get_fiq_regs(struct pt_regs *regs)
 129 {
 130         register unsigned long tmp, tmp2;
 131         __asm__ volatile (
 132         "mrs    %0, cpsr\n\
 133         mov     %1, %3\n\
 134         msr     cpsr_c, %1      @ select FIQ mode\n\
 135         mov     r0, r0\n\
 136         stmia   %2, {r8 - r14}\n\
 137         msr     cpsr_c, %0      @ return to SVC mode\n\
 138         mov     r0, r0"
 139         : "=&r" (tmp), "=&r" (tmp2)
 140         : "r" (&regs->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE)
 141         /* These registers aren't modified by the above code in a way
 142            visible to the compiler, but we mark them as clobbers anyway
 143            so that GCC won't put any of the input or output operands in
 144            them.  */
 145         : "r8", "r9", "r10", "r11", "r12", "r13", "r14");
 146 }
 147
 148 int claim_fiq(struct fiq_handler *f)
 149 {
 150         int ret = 0;
 151
 152         if (current_fiq) {
 153                 ret = -EBUSY;
 154
 155                 if (current_fiq->fiq_op != NULL)
 156                         ret = current_fiq->fiq_op(current_fiq->dev_id, 1);
 157         }
 158
 159         if (!ret) {
 160                 f->next = current_fiq;
 161                 current_fiq = f;
 162         }
 163
 164         return ret;
 165 }
 166
 167 void release_fiq(struct fiq_handler *f)
 168 {
 169         if (current_fiq != f) {
 170                 printk(KERN_ERR "%s FIQ trying to release %s FIQ\n",
 171                        f->name, current_fiq->name);
 172                 dump_stack();
 173                 return;
 174         }
 175
 176         do
 177                 current_fiq = current_fiq->next;
 178         while (current_fiq->fiq_op(current_fiq->dev_id, 0));
 179 }
 180
 181 void enable_fiq(int fiq)
 182 {
 183         enable_irq(fiq + FIQ_START);
 184 }
 185
 186 void disable_fiq(int fiq)
 187 {
 188         disable_irq(fiq + FIQ_START);
 189 }
 190
 191 EXPORT_SYMBOL(set_fiq_handler);
 192 EXPORT_SYMBOL(set_fiq_regs);
 193 EXPORT_SYMBOL(get_fiq_regs);
 194 EXPORT_SYMBOL(claim_fiq);
 195 EXPORT_SYMBOL(release_fiq);
 196 EXPORT_SYMBOL(enable_fiq);
 197 EXPORT_SYMBOL(disable_fiq);
 198
 199 void __init init_FIQ(void)
 200 {
 201         no_fiq_insn = *(unsigned long *)FIQ_VECTOR;
 202         set_fs(get_fs());
 203 }