arch/mips/kernel/idle.c

   1 /*
   2  * MIPS idle loop and WAIT instruction support.
   3  *
   4  * Copyright (C) xxxx  the Anonymous
   5  * Copyright (C) 1994 - 2006 Ralf Baechle
   6  * Copyright (C) 2003, 2004  Maciej W. Rozycki
   7  * Copyright (C) 2001, 2004, 2011, 2012  MIPS Technologies, Inc.
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License
  11  * as published by the Free Software Foundation; either version
  12  * 2 of the License, or (at your option) any later version.
  13  */
  14 #include <linux/export.h>
  15 #include <linux/init.h>
  16 #include <linux/irqflags.h>
  17 #include <linux/printk.h>
  18 #include <linux/sched.h>
  19 #include <asm/cpu.h>
  20 #include <asm/cpu-info.h>
  21 #include <asm/cpu-type.h>
  22 #include <asm/idle.h>
  23 #include <asm/mipsregs.h>
  24
  25 /*
  26  * Not all of the MIPS CPUs have the "wait" instruction available. Moreover,
  27  * the implementation of the "wait" feature differs between CPU families. This
  28  * points to the function that implements CPU specific wait.
  29  * The wait instruction stops the pipeline and reduces the power consumption of
  30  * the CPU very much.
  31  */
  32 void (*cpu_wait)(void);
  33 EXPORT_SYMBOL(cpu_wait);
  34
  35 static void r3081_wait(void)
  36 {
  37         unsigned long cfg = read_c0_conf();
  38         write_c0_conf(cfg | R30XX_CONF_HALT);
  39         local_irq_enable();
  40 }
  41
  42 static void r39xx_wait(void)
  43 {
  44         if (!need_resched())
  45                 write_c0_conf(read_c0_conf() | TX39_CONF_HALT);
  46         local_irq_enable();
  47 }
  48
  49 void r4k_wait(void)
  50 {
  51         local_irq_enable();
  52         __r4k_wait();
  53 }
  54
  55 /*
  56  * This variant is preferable as it allows testing need_resched and going to
  57  * sleep depending on the outcome atomically.  Unfortunately the "It is
  58  * implementation-dependent whether the pipeline restarts when a non-enabled
  59  * interrupt is requested" restriction in the MIPS32/MIPS64 architecture makes
  60  * using this version a gamble.
  61  */
  62 void r4k_wait_irqoff(void)
  63 {
  64         if (!need_resched())
  65                 __asm__(
  66                 "       .set    push            \n"
  67                 "       .set    mips3           \n"
  68                 "       wait                    \n"
  69                 "       .set    pop             \n");
  70         local_irq_enable();
  71         __asm__(
  72         "       .globl __pastwait       \n"
  73         "__pastwait:                    \n");
  74 }
  75
  76 /*
  77  * The RM7000 variant has to handle erratum 38.  The workaround is to not
  78  * have any pending stores when the WAIT instruction is executed.
  79  */
  80 static void rm7k_wait_irqoff(void)
  81 {
  82         if (!need_resched())
  83                 __asm__(
  84                 "       .set    push                                    \n"
  85                 "       .set    mips3                                   \n"
  86                 "       .set    noat                                    \n"
  87                 "       mfc0    $1, $12                                 \n"
  88                 "       sync                                            \n"
  89                 "       mtc0    $1, $12         # stalls until W stage  \n"
  90                 "       wait                                            \n"
  91                 "       mtc0    $1, $12         # stalls until W stage  \n"
  92                 "       .set    pop                                     \n");
  93         local_irq_enable();
  94 }
  95
  96 /*
  97  * Au1 'wait' is only useful when the 32kHz counter is used as timer,
  98  * since coreclock (and the cp0 counter) stops upon executing it. Only an
  99  * interrupt can wake it, so they must be enabled before entering idle modes.
 100  */
 101 static void au1k_wait(void)
 102 {
 103         unsigned long c0status = read_c0_status() | 1;  /* irqs on */
 104
 105         __asm__(
 106         "       .set    mips3                   \n"
 107         "       cache   0x14, 0(%0)             \n"
 108         "       cache   0x14, 32(%0)            \n"
 109         "       sync                            \n"
 110         "       mtc0    %1, $12                 \n" /* wr c0status */
 111         "       wait                            \n"
 112         "       nop                             \n"
 113         "       nop                             \n"
 114         "       nop                             \n"
 115         "       nop                             \n"
 116         "       .set    mips0                   \n"
 117         : : "r" (au1k_wait), "r" (c0status));
 118 }
 119
 120 static int __initdata nowait;
 121
 122 static int __init wait_disable(char *s)
 123 {
 124         nowait = 1;
 125
 126         return 1;
 127 }
 128
 129 __setup("nowait", wait_disable);
 130
 131 void __init check_wait(void)
 132 {
 133         struct cpuinfo_mips *c = &current_cpu_data;
 134
 135         if (nowait) {
 136                 printk("Wait instruction disabled.\n");
 137                 return;
 138         }
 139
 140         switch (current_cpu_type()) {
 141         case CPU_R3081:
 142         case CPU_R3081E:
 143                 cpu_wait = r3081_wait;
 144                 break;
 145         case CPU_TX3927:
 146                 cpu_wait = r39xx_wait;
 147                 break;
 148         case CPU_R4200:
 149 /*      case CPU_R4300: */
 150         case CPU_R4600:
 151         case CPU_R4640:
 152         case CPU_R4650:
 153         case CPU_R4700:
 154         case CPU_R5000:
 155         case CPU_R5500:
 156         case CPU_NEVADA:
 157         case CPU_4KC:
 158         case CPU_4KEC:
 159         case CPU_4KSC:
 160         case CPU_5KC:
 161         case CPU_25KF:
 162         case CPU_PR4450:
 163         case CPU_BMIPS3300:
 164         case CPU_BMIPS4350:
 165         case CPU_BMIPS4380:
 166         case CPU_BMIPS5000:
 167         case CPU_CAVIUM_OCTEON:
 168         case CPU_CAVIUM_OCTEON_PLUS:
 169         case CPU_CAVIUM_OCTEON2:
 170         case CPU_CAVIUM_OCTEON3:
 171         case CPU_JZRISC:
 172         case CPU_LOONGSON1:
 173         case CPU_XLR:
 174         case CPU_XLP:
 175                 cpu_wait = r4k_wait;
 176                 break;
 177
 178         case CPU_RM7000:
 179                 cpu_wait = rm7k_wait_irqoff;
 180                 break;
 181
 182         case CPU_M14KC:
 183         case CPU_M14KEC:
 184         case CPU_24K:
 185         case CPU_34K:
 186         case CPU_1004K:
 187                 cpu_wait = r4k_wait;
 188                 if (read_c0_config7() & MIPS_CONF7_WII)
 189                         cpu_wait = r4k_wait_irqoff;
 190                 break;
 191
 192         case CPU_74K:
 193                 cpu_wait = r4k_wait;
 194                 if ((c->processor_id & 0xff) >= PRID_REV_ENCODE_332(2, 1, 0))
 195                         cpu_wait = r4k_wait_irqoff;
 196                 break;
 197
 198         case CPU_TX49XX:
 199                 cpu_wait = r4k_wait_irqoff;
 200                 break;
 201         case CPU_ALCHEMY:
 202                 cpu_wait = au1k_wait;
 203                 break;
 204         case CPU_20KC:
 205                 /*
 206                  * WAIT on Rev1.0 has E1, E2, E3 and E16.
 207                  * WAIT on Rev2.0 and Rev3.0 has E16.
 208                  * Rev3.1 WAIT is nop, why bother
 209                  */
 210                 if ((c->processor_id & 0xff) <= 0x64)
 211                         break;
 212
 213                 /*
 214                  * Another rev is incremeting c0_count at a reduced clock
 215                  * rate while in WAIT mode.  So we basically have the choice
 216                  * between using the cp0 timer as clocksource or avoiding
 217                  * the WAIT instruction.  Until more details are known,
 218                  * disable the use of WAIT for 20Kc entirely.
 219                    cpu_wait = r4k_wait;
 220                  */
 221                 break;
 222         case CPU_RM9000:
 223                 if ((c->processor_id & 0x00ff) >= 0x40)
 224                         cpu_wait = r4k_wait;
 225                 break;
 226         default:
 227                 break;
 228         }
 229 }
 230
 231 static void smtc_idle_hook(void)
 232 {
 233 #ifdef CONFIG_MIPS_MT_SMTC
 234         void smtc_idle_loop_hook(void);
 235
 236         smtc_idle_loop_hook();
 237 #endif
 238 }
 239
 240 void arch_cpu_idle(void)
 241 {
 242         smtc_idle_hook();
 243         if (cpu_wait)
 244                 cpu_wait();
 245         else
 246                 local_irq_enable();
 247 }