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 = ¤t_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_LOONGSON1: 177 case CPU_XLR: 178 case CPU_XLP: 179 cpu_wait = r4k_wait; 180 break; 181 case CPU_LOONGSON3: 182 if ((c->processor_id & PRID_REV_MASK) >= PRID_REV_LOONGSON3A_R2_0) 183 cpu_wait = r4k_wait; 184 break; 185 186 case CPU_BMIPS5000: 187 cpu_wait = r4k_wait_irqoff; 188 break; 189 case CPU_RM7000: 190 cpu_wait = rm7k_wait_irqoff; 191 break; 192 193 case CPU_PROAPTIV: 194 case CPU_P5600: 195 /* 196 * Incoming Fast Debug Channel (FDC) data during a wait 197 * instruction causes the wait never to resume, even if an 198 * interrupt is received. Avoid using wait at all if FDC data is 199 * likely to be received. 200 */ 201 if (IS_ENABLED(CONFIG_MIPS_EJTAG_FDC_TTY)) 202 break; 203 /* fall through */ 204 case CPU_M14KC: 205 case CPU_M14KEC: 206 case CPU_24K: 207 case CPU_34K: 208 case CPU_1004K: 209 case CPU_1074K: 210 case CPU_INTERAPTIV: 211 case CPU_M5150: 212 case CPU_QEMU_GENERIC: 213 cpu_wait = r4k_wait; 214 if (read_c0_config7() & MIPS_CONF7_WII) 215 cpu_wait = r4k_wait_irqoff; 216 break; 217 218 case CPU_74K: 219 cpu_wait = r4k_wait; 220 if ((c->processor_id & 0xff) >= PRID_REV_ENCODE_332(2, 1, 0)) 221 cpu_wait = r4k_wait_irqoff; 222 break; 223 224 case CPU_TX49XX: 225 cpu_wait = r4k_wait_irqoff; 226 break; 227 case CPU_ALCHEMY: 228 cpu_wait = au1k_wait; 229 break; 230 case CPU_20KC: 231 /* 232 * WAIT on Rev1.0 has E1, E2, E3 and E16. 233 * WAIT on Rev2.0 and Rev3.0 has E16. 234 * Rev3.1 WAIT is nop, why bother 235 */ 236 if ((c->processor_id & 0xff) <= 0x64) 237 break; 238 239 /* 240 * Another rev is incremeting c0_count at a reduced clock 241 * rate while in WAIT mode. So we basically have the choice 242 * between using the cp0 timer as clocksource or avoiding 243 * the WAIT instruction. Until more details are known, 244 * disable the use of WAIT for 20Kc entirely. 245 cpu_wait = r4k_wait; 246 */ 247 break; 248 default: 249 break; 250 } 251 } 252 253 void arch_cpu_idle(void) 254 { 255 if (cpu_wait) 256 cpu_wait(); 257 else 258 local_irq_enable(); 259 } 260 261 #ifdef CONFIG_CPU_IDLE 262 263 int mips_cpuidle_wait_enter(struct cpuidle_device *dev, 264 struct cpuidle_driver *drv, int index) 265 { 266 arch_cpu_idle(); 267 return index; 268 } 269 270 #endif 271