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