arch/mips/kernel/idle.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * MIPS idle loop and WAIT instruction support.
   4  *
   5  * Copyright (C) xxxx  the Anonymous
   6  * Copyright (C) 1994 - 2006 Ralf Baechle
   7  * Copyright (C) 2003, 2004  Maciej W. Rozycki
   8  * Copyright (C) 2001, 2004, 2011, 2012  MIPS Technologies, Inc.
   9  */
  10 #include <linux/cpu.h>
  11 #include <linux/export.h>
  12 #include <linux/init.h>
  13 #include <linux/irqflags.h>
  14 #include <linux/printk.h>
  15 #include <linux/sched.h>
  16 #include <asm/cpu.h>
  17 #include <asm/cpu-info.h>
  18 #include <asm/cpu-type.h>
  19 #include <asm/idle.h>
  20 #include <asm/mipsregs.h>
  21
  22 /*
  23  * Not all of the MIPS CPUs have the "wait" instruction available. Moreover,
  24  * the implementation of the "wait" feature differs between CPU families. This
  25  * points to the function that implements CPU specific wait.
  26  * The wait instruction stops the pipeline and reduces the power consumption of
  27  * the CPU very much.
  28  */
  29 void (*cpu_wait)(void);
  30 EXPORT_SYMBOL(cpu_wait);
  31
  32 static void __cpuidle r3081_wait(void)
  33 {
  34         unsigned long cfg = read_c0_conf();
  35         write_c0_conf(cfg | R30XX_CONF_HALT);
  36         local_irq_enable();
  37 }
  38
  39 static void __cpuidle r39xx_wait(void)
  40 {
  41         if (!need_resched())
  42                 write_c0_conf(read_c0_conf() | TX39_CONF_HALT);
  43         local_irq_enable();
  44 }
  45
  46 void __cpuidle r4k_wait(void)
  47 {
  48         local_irq_enable();
  49         __r4k_wait();
  50 }
  51
  52 /*
  53  * This variant is preferable as it allows testing need_resched and going to
  54  * sleep depending on the outcome atomically.  Unfortunately the "It is
  55  * implementation-dependent whether the pipeline restarts when a non-enabled
  56  * interrupt is requested" restriction in the MIPS32/MIPS64 architecture makes
  57  * using this version a gamble.
  58  */
  59 void __cpuidle r4k_wait_irqoff(void)
  60 {
  61         if (!need_resched())
  62                 __asm__(
  63                 "       .set    push            \n"
  64                 "       .set    arch=r4000      \n"
  65                 "       wait                    \n"
  66                 "       .set    pop             \n");
  67         local_irq_enable();
  68 }
  69
  70 /*
  71  * The RM7000 variant has to handle erratum 38.  The workaround is to not
  72  * have any pending stores when the WAIT instruction is executed.
  73  */
  74 static void __cpuidle rm7k_wait_irqoff(void)
  75 {
  76         if (!need_resched())
  77                 __asm__(
  78                 "       .set    push                                    \n"
  79                 "       .set    arch=r4000                              \n"
  80                 "       .set    noat                                    \n"
  81                 "       mfc0    $1, $12                                 \n"
  82                 "       sync                                            \n"
  83                 "       mtc0    $1, $12         # stalls until W stage  \n"
  84                 "       wait                                            \n"
  85                 "       mtc0    $1, $12         # stalls until W stage  \n"
  86                 "       .set    pop                                     \n");
  87         local_irq_enable();
  88 }
  89
  90 /*
  91  * Au1 'wait' is only useful when the 32kHz counter is used as timer,
  92  * since coreclock (and the cp0 counter) stops upon executing it. Only an
  93  * interrupt can wake it, so they must be enabled before entering idle modes.
  94  */
  95 static void __cpuidle au1k_wait(void)
  96 {
  97         unsigned long c0status = read_c0_status() | 1;  /* irqs on */
  98
  99         __asm__(
 100         "       .set    push                    \n"
 101         "       .set    arch=r4000              \n"
 102         "       cache   0x14, 0(%0)             \n"
 103         "       cache   0x14, 32(%0)            \n"
 104         "       sync                            \n"
 105         "       mtc0    %1, $12                 \n" /* wr c0status */
 106         "       wait                            \n"
 107         "       nop                             \n"
 108         "       nop                             \n"
 109         "       nop                             \n"
 110         "       nop                             \n"
 111         "       .set    pop                     \n"
 112         : : "r" (au1k_wait), "r" (c0status));
 113 }
 114
 115 static int __initdata nowait;
 116
 117 static int __init wait_disable(char *s)
 118 {
 119         nowait = 1;
 120
 121         return 1;
 122 }
 123
 124 __setup("nowait", wait_disable);
 125
 126 void __init check_wait(void)
 127 {
 128         struct cpuinfo_mips *c = &current_cpu_data;
 129
 130         if (nowait) {
 131                 printk("Wait instruction disabled.\n");
 132                 return;
 133         }
 134
 135         /*
 136          * MIPSr6 specifies that masked interrupts should unblock an executing
 137          * wait instruction, and thus that it is safe for us to use
 138          * r4k_wait_irqoff. Yippee!
 139          */
 140         if (cpu_has_mips_r6) {
 141                 cpu_wait = r4k_wait_irqoff;
 142                 return;
 143         }
 144
 145         switch (current_cpu_type()) {
 146         case CPU_R3081:
 147         case CPU_R3081E:
 148                 cpu_wait = r3081_wait;
 149                 break;
 150         case CPU_TX3927:
 151                 cpu_wait = r39xx_wait;
 152                 break;
 153         case CPU_R4200:
 154         case CPU_R4600:
 155         case CPU_R4640:
 156         case CPU_R4650:
 157         case CPU_R4700:
 158         case CPU_R5000:
 159         case CPU_R5500:
 160         case CPU_NEVADA:
 161         case CPU_4KC:
 162         case CPU_4KEC:
 163         case CPU_4KSC:
 164         case CPU_5KC:
 165         case CPU_5KE:
 166         case CPU_25KF:
 167         case CPU_PR4450:
 168         case CPU_BMIPS3300:
 169         case CPU_BMIPS4350:
 170         case CPU_BMIPS4380:
 171         case CPU_CAVIUM_OCTEON:
 172         case CPU_CAVIUM_OCTEON_PLUS:
 173         case CPU_CAVIUM_OCTEON2:
 174         case CPU_CAVIUM_OCTEON3:
 175         case CPU_XBURST:
 176         case CPU_LOONGSON32:
 177         case CPU_XLR:
 178         case CPU_XLP:
 179                 cpu_wait = r4k_wait;
 180                 break;
 181         case CPU_LOONGSON64:
 182                 if ((c->processor_id & (PRID_IMP_MASK | PRID_REV_MASK)) >=
 183                                 (PRID_IMP_LOONGSON_64C | PRID_REV_LOONGSON3A_R2_0))
 184                         cpu_wait = r4k_wait;
 185                 break;
 186
 187         case CPU_BMIPS5000:
 188                 cpu_wait = r4k_wait_irqoff;
 189                 break;
 190         case CPU_RM7000:
 191                 cpu_wait = rm7k_wait_irqoff;
 192                 break;
 193
 194         case CPU_PROAPTIV:
 195         case CPU_P5600:
 196                 /*
 197                  * Incoming Fast Debug Channel (FDC) data during a wait
 198                  * instruction causes the wait never to resume, even if an
 199                  * interrupt is received. Avoid using wait at all if FDC data is
 200                  * likely to be received.
 201                  */
 202                 if (IS_ENABLED(CONFIG_MIPS_EJTAG_FDC_TTY))
 203                         break;
 204                 /* fall through */
 205         case CPU_M14KC:
 206         case CPU_M14KEC:
 207         case CPU_24K:
 208         case CPU_34K:
 209         case CPU_1004K:
 210         case CPU_1074K:
 211         case CPU_INTERAPTIV:
 212         case CPU_M5150:
 213         case CPU_QEMU_GENERIC:
 214                 cpu_wait = r4k_wait;
 215                 if (read_c0_config7() & MIPS_CONF7_WII)
 216                         cpu_wait = r4k_wait_irqoff;
 217                 break;
 218
 219         case CPU_74K:
 220                 cpu_wait = r4k_wait;
 221                 if ((c->processor_id & 0xff) >= PRID_REV_ENCODE_332(2, 1, 0))
 222                         cpu_wait = r4k_wait_irqoff;
 223                 break;
 224
 225         case CPU_TX49XX:
 226                 cpu_wait = r4k_wait_irqoff;
 227                 break;
 228         case CPU_ALCHEMY:
 229                 cpu_wait = au1k_wait;
 230                 break;
 231         case CPU_20KC:
 232                 /*
 233                  * WAIT on Rev1.0 has E1, E2, E3 and E16.
 234                  * WAIT on Rev2.0 and Rev3.0 has E16.
 235                  * Rev3.1 WAIT is nop, why bother
 236                  */
 237                 if ((c->processor_id & 0xff) <= 0x64)
 238                         break;
 239
 240                 /*
 241                  * Another rev is incremeting c0_count at a reduced clock
 242                  * rate while in WAIT mode.  So we basically have the choice
 243                  * between using the cp0 timer as clocksource or avoiding
 244                  * the WAIT instruction.  Until more details are known,
 245                  * disable the use of WAIT for 20Kc entirely.
 246                    cpu_wait = r4k_wait;
 247                  */
 248                 break;
 249         default:
 250                 break;
 251         }
 252 }
 253
 254 void arch_cpu_idle(void)
 255 {
 256         if (cpu_wait)
 257                 cpu_wait();
 258         else
 259                 local_irq_enable();
 260 }
 261
 262 #ifdef CONFIG_CPU_IDLE
 263
 264 int mips_cpuidle_wait_enter(struct cpuidle_device *dev,
 265                             struct cpuidle_driver *drv, int index)
 266 {
 267         arch_cpu_idle();
 268         return index;
 269 }
 270
 271 #endif