arch/mips/kernel/watch.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 2008 David Daney
   7  */
   8
   9 #include <linux/sched.h>
  10
  11 #include <asm/processor.h>
  12 #include <asm/watch.h>
  13
  14 /*
  15  * Install the watch registers for the current thread.  A maximum of
  16  * four registers are installed although the machine may have more.
  17  */
  18 void mips_install_watch_registers(struct task_struct *t)
  19 {
  20         struct mips3264_watch_reg_state *watches = &t->thread.watch.mips3264;
  21         switch (current_cpu_data.watch_reg_use_cnt) {
  22         default:
  23                 BUG();
  24         case 4:
  25                 write_c0_watchlo3(watches->watchlo[3]);
  26                 /* Write 1 to the I, R, and W bits to clear them, and
  27                    1 to G so all ASIDs are trapped. */
  28                 write_c0_watchhi3(MIPS_WATCHHI_G | MIPS_WATCHHI_IRW |
  29                                   watches->watchhi[3]);
  30         case 3:
  31                 write_c0_watchlo2(watches->watchlo[2]);
  32                 write_c0_watchhi2(MIPS_WATCHHI_G | MIPS_WATCHHI_IRW |
  33                                   watches->watchhi[2]);
  34         case 2:
  35                 write_c0_watchlo1(watches->watchlo[1]);
  36                 write_c0_watchhi1(MIPS_WATCHHI_G | MIPS_WATCHHI_IRW |
  37                                   watches->watchhi[1]);
  38         case 1:
  39                 write_c0_watchlo0(watches->watchlo[0]);
  40                 write_c0_watchhi0(MIPS_WATCHHI_G | MIPS_WATCHHI_IRW |
  41                                   watches->watchhi[0]);
  42         }
  43 }
  44
  45 /*
  46  * Read back the watchhi registers so the user space debugger has
  47  * access to the I, R, and W bits.  A maximum of four registers are
  48  * read although the machine may have more.
  49  */
  50 void mips_read_watch_registers(void)
  51 {
  52         struct mips3264_watch_reg_state *watches =
  53                 &current->thread.watch.mips3264;
  54         switch (current_cpu_data.watch_reg_use_cnt) {
  55         default:
  56                 BUG();
  57         case 4:
  58                 watches->watchhi[3] = (read_c0_watchhi3() &
  59                                        (MIPS_WATCHHI_MASK | MIPS_WATCHHI_IRW));
  60         case 3:
  61                 watches->watchhi[2] = (read_c0_watchhi2() &
  62                                        (MIPS_WATCHHI_MASK | MIPS_WATCHHI_IRW));
  63         case 2:
  64                 watches->watchhi[1] = (read_c0_watchhi1() &
  65                                        (MIPS_WATCHHI_MASK | MIPS_WATCHHI_IRW));
  66         case 1:
  67                 watches->watchhi[0] = (read_c0_watchhi0() &
  68                                        (MIPS_WATCHHI_MASK | MIPS_WATCHHI_IRW));
  69         }
  70         if (current_cpu_data.watch_reg_use_cnt == 1 &&
  71             (watches->watchhi[0] & MIPS_WATCHHI_IRW) == 0) {
  72                 /* Pathological case of release 1 architecture that
  73                  * doesn't set the condition bits.  We assume that
  74                  * since we got here, the watch condition was met and
  75                  * signal that the conditions requested in watchlo
  76                  * were met.  */
  77                 watches->watchhi[0] |= (watches->watchlo[0] & MIPS_WATCHHI_IRW);
  78         }
  79  }
  80
  81 /*
  82  * Disable all watch registers.  Although only four registers are
  83  * installed, all are cleared to eliminate the possibility of endless
  84  * looping in the watch handler.
  85  */
  86 void mips_clear_watch_registers(void)
  87 {
  88         switch (current_cpu_data.watch_reg_count) {
  89         default:
  90                 BUG();
  91         case 8:
  92                 write_c0_watchlo7(0);
  93         case 7:
  94                 write_c0_watchlo6(0);
  95         case 6:
  96                 write_c0_watchlo5(0);
  97         case 5:
  98                 write_c0_watchlo4(0);
  99         case 4:
 100                 write_c0_watchlo3(0);
 101         case 3:
 102                 write_c0_watchlo2(0);
 103         case 2:
 104                 write_c0_watchlo1(0);
 105         case 1:
 106                 write_c0_watchlo0(0);
 107         }
 108 }
 109
 110 void mips_probe_watch_registers(struct cpuinfo_mips *c)
 111 {
 112         unsigned int t;
 113
 114         if ((c->options & MIPS_CPU_WATCH) == 0)
 115                 return;
 116         /*
 117          * Check which of the I,R and W bits are supported, then
 118          * disable the register.
 119          */
 120         write_c0_watchlo0(MIPS_WATCHLO_IRW);
 121         back_to_back_c0_hazard();
 122         t = read_c0_watchlo0();
 123         write_c0_watchlo0(0);
 124         c->watch_reg_masks[0] = t & MIPS_WATCHLO_IRW;
 125
 126         /* Write the mask bits and read them back to determine which
 127          * can be used. */
 128         c->watch_reg_count = 1;
 129         c->watch_reg_use_cnt = 1;
 130         t = read_c0_watchhi0();
 131         write_c0_watchhi0(t | MIPS_WATCHHI_MASK);
 132         back_to_back_c0_hazard();
 133         t = read_c0_watchhi0();
 134         c->watch_reg_masks[0] |= (t & MIPS_WATCHHI_MASK);
 135         if ((t & MIPS_WATCHHI_M) == 0)
 136                 return;
 137
 138         write_c0_watchlo1(MIPS_WATCHLO_IRW);
 139         back_to_back_c0_hazard();
 140         t = read_c0_watchlo1();
 141         write_c0_watchlo1(0);
 142         c->watch_reg_masks[1] = t & MIPS_WATCHLO_IRW;
 143
 144         c->watch_reg_count = 2;
 145         c->watch_reg_use_cnt = 2;
 146         t = read_c0_watchhi1();
 147         write_c0_watchhi1(t | MIPS_WATCHHI_MASK);
 148         back_to_back_c0_hazard();
 149         t = read_c0_watchhi1();
 150         c->watch_reg_masks[1] |= (t & MIPS_WATCHHI_MASK);
 151         if ((t & MIPS_WATCHHI_M) == 0)
 152                 return;
 153
 154         write_c0_watchlo2(MIPS_WATCHLO_IRW);
 155         back_to_back_c0_hazard();
 156         t = read_c0_watchlo2();
 157         write_c0_watchlo2(0);
 158         c->watch_reg_masks[2] = t & MIPS_WATCHLO_IRW;
 159
 160         c->watch_reg_count = 3;
 161         c->watch_reg_use_cnt = 3;
 162         t = read_c0_watchhi2();
 163         write_c0_watchhi2(t | MIPS_WATCHHI_MASK);
 164         back_to_back_c0_hazard();
 165         t = read_c0_watchhi2();
 166         c->watch_reg_masks[2] |= (t & MIPS_WATCHHI_MASK);
 167         if ((t & MIPS_WATCHHI_M) == 0)
 168                 return;
 169
 170         write_c0_watchlo3(MIPS_WATCHLO_IRW);
 171         back_to_back_c0_hazard();
 172         t = read_c0_watchlo3();
 173         write_c0_watchlo3(0);
 174         c->watch_reg_masks[3] = t & MIPS_WATCHLO_IRW;
 175
 176         c->watch_reg_count = 4;
 177         c->watch_reg_use_cnt = 4;
 178         t = read_c0_watchhi3();
 179         write_c0_watchhi3(t | MIPS_WATCHHI_MASK);
 180         back_to_back_c0_hazard();
 181         t = read_c0_watchhi3();
 182         c->watch_reg_masks[3] |= (t & MIPS_WATCHHI_MASK);
 183         if ((t & MIPS_WATCHHI_M) == 0)
 184                 return;
 185
 186         /* We use at most 4, but probe and report up to 8. */
 187         c->watch_reg_count = 5;
 188         t = read_c0_watchhi4();
 189         if ((t & MIPS_WATCHHI_M) == 0)
 190                 return;
 191
 192         c->watch_reg_count = 6;
 193         t = read_c0_watchhi5();
 194         if ((t & MIPS_WATCHHI_M) == 0)
 195                 return;
 196
 197         c->watch_reg_count = 7;
 198         t = read_c0_watchhi6();
 199         if ((t & MIPS_WATCHHI_M) == 0)
 200                 return;
 201
 202         c->watch_reg_count = 8;
 203 }