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/cpu.h>
  15 #include <linux/export.h>
  16 #include <linux/init.h>
  17 #include <linux/irqflags.h>
  18 #include <linux/printk.h>
  19 #include <linux/sched.h>
  20 #include <asm/cpu.h>
  21 #include <asm/cpu-info.h>
  22 #include <asm/cpu-type.h>
  23 #include <asm/idle.h>
  24 #include <asm/mipsregs.h>
  25
  26 /*
  27  * Not all of the MIPS CPUs have the "wait" instruction available. Moreover,
  28  * the implementation of the "wait" feature differs between CPU families. This
  29  * points to the function that implements CPU specific wait.
  30  * The wait instruction stops the pipeline and reduces the power consumption of
  31  * the CPU very much.
  32  */
  33 void (*cpu_wait)(void);
  34 EXPORT_SYMBOL(cpu_wait);
  35
  36 static void r3081_wait(void)
  37 {
  38         unsigned long cfg = read_c0_conf();
  39         write_c0_conf(cfg | R30XX_CONF_HALT);
  40         local_irq_enable();
  41 }
  42
  43 static void r39xx_wait(void)
  44 {
  45         if (!need_resched())
  46                 write_c0_conf(read_c0_conf() | TX39_CONF_HALT);
  47         local_irq_enable();
  48 }
  49
  50 void r4k_wait(void)
  51 {
  52         local_irq_enable();
  53         __r4k_wait();
  54 }
  55
  56 /*
  57  * This variant is preferable as it allows testing need_resched and going to
  58  * sleep depending on the outcome atomically.  Unfortunately the "It is
  59  * implementation-dependent whether the pipeline restarts when a non-enabled
  60  * interrupt is requested" restriction in the MIPS32/MIPS64 architecture makes
  61  * using this version a gamble.
  62  */
  63 void r4k_wait_irqoff(void)
  64 {
  65         if (!need_resched())
  66                 __asm__(
  67                 "       .set    push            \n"
  68                 "       .set    arch=r4000      \n"
  69                 "       wait                    \n"
  70                 "       .set    pop             \n");
  71         local_irq_enable();
  72 }
  73
  74 /*
  75  * The RM7000 variant has to handle erratum 38.  The workaround is to not
  76  * have any pending stores when the WAIT instruction is executed.
  77  */
  78 static void rm7k_wait_irqoff(void)
  79 {
  80         if (!need_resched())
  81                 __asm__(
  82                 "       .set    push                                    \n"
  83                 "       .set    arch=r4000                              \n"
  84                 "       .set    noat                                    \n"
  85                 "       mfc0    $1, $12                                 \n"
  86                 "       sync                                            \n"
  87                 "       mtc0    $1, $12         # stalls until W stage  \n"
  88                 "       wait                                            \n"
  89                 "       mtc0    $1, $12         # stalls until W stage  \n"
  90                 "       .set    pop                                     \n");
  91         local_irq_enable();
  92 }
  93
  94 /*
  95  * Au1 'wait' is only useful when the 32kHz counter is used as timer,
  96  * since coreclock (and the cp0 counter) stops upon executing it. Only an
  97  * interrupt can wake it, so they must be enabled before entering idle modes.
  98  */
  99 static void au1k_wait(void)
 100 {
 101         unsigned long c0status = read_c0_status() | 1;  /* irqs on */
 102
 103         __asm__(
 104         "       .set    arch=r4000                      \n"
 105         "       cache   0x14, 0(%0)             \n"
 106         "       cache   0x14, 32(%0)            \n"
 107         "       sync                            \n"
 108         "       mtc0    %1, $12                 \n" /* wr c0status */
 109         "       wait                            \n"
 110         "       nop                             \n"
 111         "       nop                             \n"
 112         "       nop                             \n"
 113         "       nop                             \n"
 114         "       .set    mips0                   \n"
 115         : : "r" (au1k_wait), "r" (c0status));
 116 }
 117
 118 static int __initdata nowait;
 119
 120 static int __init wait_disable(char *s)
 121 {
 122         nowait = 1;
 123
 124         return 1;
 125 }
 126
 127 __setup("nowait", wait_disable);
 128
 129 void __init check_wait(void)
 130 {
 131         struct cpuinfo_mips *c = &current_cpu_data;
 132
 133         if (nowait) {
 134                 printk("Wait instruction disabled.\n");
 135                 return;
 136         }
 137
 138         /*
 139          * MIPSr6 specifies that masked interrupts should unblock an executing
 140          * wait instruction, and thus that it is safe for us to use
 141          * r4k_wait_irqoff. Yippee!
 142          */
 143         if (cpu_has_mips_r6) {
 144                 cpu_wait = r4k_wait_irqoff;
 145                 return;
 146         }
 147
 148         switch (current_cpu_type()) {
 149         case CPU_R3081:
 150         case CPU_R3081E:
 151                 cpu_wait = r3081_wait;
 152                 break;
 153         case CPU_TX3927:
 154                 cpu_wait = r39xx_wait;
 155                 break;
 156         case CPU_R4200:
 157 /*      case CPU_R4300: */
 158         case CPU_R4600:
 159         case CPU_R4640:
 160         case CPU_R4650:
 161         case CPU_R4700:
 162         case CPU_R5000:
 163         case CPU_R5500:
 164         case CPU_NEVADA:
 165         case CPU_4KC:
 166         case CPU_4KEC:
 167         case CPU_4KSC:
 168         case CPU_5KC:
 169         case CPU_5KE:
 170         case CPU_25KF:
 171         case CPU_PR4450:
 172         case CPU_BMIPS3300:
 173         case CPU_BMIPS4350:
 174         case CPU_BMIPS4380:
 175         case CPU_CAVIUM_OCTEON:
 176         case CPU_CAVIUM_OCTEON_PLUS:
 177         case CPU_CAVIUM_OCTEON2:
 178         case CPU_CAVIUM_OCTEON3:
 179         case CPU_JZRISC:
 180         case CPU_LOONGSON1:
 181         case CPU_XLR:
 182         case CPU_XLP:
 183                 cpu_wait = r4k_wait;
 184                 break;
 185         case CPU_LOONGSON3:
 186                 if ((c->processor_id & PRID_REV_MASK) >= PRID_REV_LOONGSON3A_R2)
 187                         cpu_wait = r4k_wait;
 188                 break;
 189
 190         case CPU_BMIPS5000:
 191                 cpu_wait = r4k_wait_irqoff;
 192                 break;
 193         case CPU_RM7000:
 194                 cpu_wait = rm7k_wait_irqoff;
 195                 break;
 196
 197         case CPU_PROAPTIV:
 198         case CPU_P5600:
 199                 /*
 200                  * Incoming Fast Debug Channel (FDC) data during a wait
 201                  * instruction causes the wait never to resume, even if an
 202                  * interrupt is received. Avoid using wait at all if FDC data is
 203                  * likely to be received.
 204                  */
 205                 if (IS_ENABLED(CONFIG_MIPS_EJTAG_FDC_TTY))
 206                         break;
 207                 /* fall through */
 208         case CPU_M14KC:
 209         case CPU_M14KEC:
 210         case CPU_24K:
 211         case CPU_34K:
 212         case CPU_1004K:
 213         case CPU_1074K:
 214         case CPU_INTERAPTIV:
 215         case CPU_M5150:
 216         case CPU_QEMU_GENERIC:
 217                 cpu_wait = r4k_wait;
 218                 if (read_c0_config7() & MIPS_CONF7_WII)
 219                         cpu_wait = r4k_wait_irqoff;
 220                 break;
 221
 222         case CPU_74K:
 223                 cpu_wait = r4k_wait;
 224                 if ((c->processor_id & 0xff) >= PRID_REV_ENCODE_332(2, 1, 0))
 225                         cpu_wait = r4k_wait_irqoff;
 226                 break;
 227
 228         case CPU_TX49XX:
 229                 cpu_wait = r4k_wait_irqoff;
 230                 break;
 231         case CPU_ALCHEMY:
 232                 cpu_wait = au1k_wait;
 233                 break;
 234         case CPU_20KC:
 235                 /*
 236                  * WAIT on Rev1.0 has E1, E2, E3 and E16.
 237                  * WAIT on Rev2.0 and Rev3.0 has E16.
 238                  * Rev3.1 WAIT is nop, why bother
 239                  */
 240                 if ((c->processor_id & 0xff) <= 0x64)
 241                         break;
 242
 243                 /*
 244                  * Another rev is incremeting c0_count at a reduced clock
 245                  * rate while in WAIT mode.  So we basically have the choice
 246                  * between using the cp0 timer as clocksource or avoiding
 247                  * the WAIT instruction.  Until more details are known,
 248                  * disable the use of WAIT for 20Kc entirely.
 249                    cpu_wait = r4k_wait;
 250                  */
 251                 break;
 252         default:
 253                 break;
 254         }
 255 }
 256
 257 void arch_cpu_idle(void)
 258 {
 259         if (cpu_wait)
 260                 cpu_wait();
 261         else
 262                 local_irq_enable();
 263 }
 264
 265 #ifdef CONFIG_CPU_IDLE
 266
 267 int mips_cpuidle_wait_enter(struct cpuidle_device *dev,
 268                             struct cpuidle_driver *drv, int index)
 269 {
 270         arch_cpu_idle();
 271         return index;
 272 }
 273
 274 #endif