arch/arm26/kernel/fiq.c

   1 /*
   2  *  linux/arch/arm26/kernel/fiq.c
   3  *
   4  *  Copyright (C) 1998 Russell King
   5  *  Copyright (C) 1998, 1999 Phil Blundell
   6  *  Copyright (C) 2003 Ian Molton
   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/config.h>
  40 #include <linux/module.h>
  41 #include <linux/mm.h>
  42 #include <linux/mman.h>
  43 #include <linux/init.h>
  44 #include <linux/seq_file.h>
  45
  46 #include <asm/fiq.h>
  47 #include <asm/io.h>
  48 #include <asm/irq.h>
  49 #include <asm/pgalloc.h>
  50 #include <asm/system.h>
  51 #include <asm/uaccess.h>
  52
  53 #define FIQ_VECTOR (vectors_base() + 0x1c)
  54
  55 static unsigned long no_fiq_insn;
  56
  57 #define unprotect_page_0()
  58 #define protect_page_0()
  59
  60 /* Default reacquire function
  61  * - we always relinquish FIQ control
  62  * - we always reacquire FIQ control
  63  */
  64 static int fiq_def_op(void *ref, int relinquish)
  65 {
  66         if (!relinquish) {
  67                 unprotect_page_0();
  68                 *(unsigned long *)FIQ_VECTOR = no_fiq_insn;
  69                 protect_page_0();
  70         }
  71
  72         return 0;
  73 }
  74
  75 static struct fiq_handler default_owner = {
  76         .name   = "default",
  77         .fiq_op = fiq_def_op,
  78 };
  79
  80 static struct fiq_handler *current_fiq = &default_owner;
  81
  82 int show_fiq_list(struct seq_file *p, void *v)
  83 {
  84         if (current_fiq != &default_owner)
  85                 seq_printf(p, "FIQ:              %s\n", current_fiq->name);
  86
  87         return 0;
  88 }
  89
  90 void set_fiq_handler(void *start, unsigned int length)
  91 {
  92         unprotect_page_0();
  93
  94         memcpy((void *)FIQ_VECTOR, start, length);
  95
  96         protect_page_0();
  97 }
  98
  99 /*
 100  * Taking an interrupt in FIQ mode is death, so both these functions
 101  * disable irqs for the duration.
 102  */
 103 void set_fiq_regs(struct pt_regs *regs)
 104 {
 105         register unsigned long tmp, tmp2;
 106         __asm__ volatile (
 107         "mov    %0, pc                                  \n"
 108         "bic    %1, %0, #0x3                            \n"
 109         "orr    %1, %1, %3                              \n"
 110         "teqp   %1, #0          @ select FIQ mode       \n"
 111         "mov    r0, r0                                  \n"
 112         "ldmia  %2, {r8 - r14}                          \n"
 113         "teqp   %0, #0          @ return to SVC mode    \n"
 114         "mov    r0, r0                                  "
 115         : "=&r" (tmp), "=&r" (tmp2)
 116         : "r" (&regs->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | MODE_FIQ26)
 117         /* These registers aren't modified by the above code in a way
 118            visible to the compiler, but we mark them as clobbers anyway
 119            so that GCC won't put any of the input or output operands in
 120            them.  */
 121         : "r8", "r9", "r10", "r11", "r12", "r13", "r14");
 122 }
 123
 124 void get_fiq_regs(struct pt_regs *regs)
 125 {
 126         register unsigned long tmp, tmp2;
 127         __asm__ volatile (
 128         "mov    %0, pc                                  \n"
 129         "bic    %1, %0, #0x3                            \n"
 130         "orr    %1, %1, %3                              \n"
 131         "teqp   %1, #0          @ select FIQ mode       \n"
 132         "mov    r0, r0                                  \n"
 133         "stmia  %2, {r8 - r14}                          \n"
 134         "teqp   %0, #0          @ return to SVC mode    \n"
 135         "mov    r0, r0                                  "
 136         : "=&r" (tmp), "=&r" (tmp2)
 137         : "r" (&regs->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | MODE_FIQ26)
 138         /* These registers aren't modified by the above code in a way
 139            visible to the compiler, but we mark them as clobbers anyway
 140            so that GCC won't put any of the input or output operands in
 141            them.  */
 142         : "r8", "r9", "r10", "r11", "r12", "r13", "r14");
 143 }
 144
 145 int claim_fiq(struct fiq_handler *f)
 146 {
 147         int ret = 0;
 148
 149         if (current_fiq) {
 150                 ret = -EBUSY;
 151
 152                 if (current_fiq->fiq_op != NULL)
 153                         ret = current_fiq->fiq_op(current_fiq->dev_id, 1);
 154         }
 155
 156         if (!ret) {
 157                 f->next = current_fiq;
 158                 current_fiq = f;
 159         }
 160
 161         return ret;
 162 }
 163
 164 void release_fiq(struct fiq_handler *f)
 165 {
 166         if (current_fiq != f) {
 167                 printk(KERN_ERR "%s FIQ trying to release %s FIQ\n",
 168                        f->name, current_fiq->name);
 169 #ifdef CONFIG_DEBUG_ERRORS
 170                 __backtrace();
 171 #endif
 172                 return;
 173         }
 174
 175         do
 176                 current_fiq = current_fiq->next;
 177         while (current_fiq->fiq_op(current_fiq->dev_id, 0));
 178 }
 179
 180 void enable_fiq(int fiq)
 181 {
 182         enable_irq(fiq + FIQ_START);
 183 }
 184
 185 void disable_fiq(int fiq)
 186 {
 187         disable_irq(fiq + FIQ_START);
 188 }
 189
 190 EXPORT_SYMBOL(set_fiq_handler);
 191 EXPORT_SYMBOL(set_fiq_regs);
 192 EXPORT_SYMBOL(get_fiq_regs);
 193 EXPORT_SYMBOL(claim_fiq);
 194 EXPORT_SYMBOL(release_fiq);
 195 EXPORT_SYMBOL(enable_fiq);
 196 EXPORT_SYMBOL(disable_fiq);
 197
 198 void __init init_FIQ(void)
 199 {
 200         no_fiq_insn = *(unsigned long *)FIQ_VECTOR;
 201         set_fs(get_fs());
 202 }