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 = ¤t_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 275