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 }
37
38 void __cpuidle r4k_wait(void)
39 {
40 raw_local_irq_enable();
41 __r4k_wait();
42 raw_local_irq_disable();
43 }
44
45 /*
46 * This variant is preferable as it allows testing need_resched and going to
47 * sleep depending on the outcome atomically. Unfortunately the "It is
48 * implementation-dependent whether the pipeline restarts when a non-enabled
49 * interrupt is requested" restriction in the MIPS32/MIPS64 architecture makes
50 * using this version a gamble.
51 */
52 void __cpuidle r4k_wait_irqoff(void)
53 {
54 if (!need_resched())
55 __asm__(
56 " .set push \n"
57 " .set arch=r4000 \n"
58 " wait \n"
59 " .set pop \n");
60 }
61
62 /*
63 * The RM7000 variant has to handle erratum 38. The workaround is to not
64 * have any pending stores when the WAIT instruction is executed.
65 */
66 static void __cpuidle rm7k_wait_irqoff(void)
67 {
68 if (!need_resched())
69 __asm__(
70 " .set push \n"
71 " .set arch=r4000 \n"
72 " .set noat \n"
73 " mfc0 $1, $12 \n"
74 " sync \n"
75 " mtc0 $1, $12 # stalls until W stage \n"
76 " wait \n"
77 " mtc0 $1, $12 # stalls until W stage \n"
78 " .set pop \n");
79 }
80
81 /*
82 * Au1 'wait' is only useful when the 32kHz counter is used as timer,
83 * since coreclock (and the cp0 counter) stops upon executing it. Only an
84 * interrupt can wake it, so they must be enabled before entering idle modes.
85 */
86 static void __cpuidle au1k_wait(void)
87 {
88 unsigned long c0status = read_c0_status() | 1; /* irqs on */
89
90 __asm__(
91 " .set push \n"
92 " .set arch=r4000 \n"
93 " cache 0x14, 0(%0) \n"
94 " cache 0x14, 32(%0) \n"
95 " sync \n"
96 " mtc0 %1, $12 \n" /* wr c0status */
97 " wait \n"
98 " nop \n"
99 " nop \n"
100 " nop \n"
101 " nop \n"
102 " .set pop \n"
103 : : "r" (au1k_wait), "r" (c0status));
104
105 raw_local_irq_disable();
106 }
107
108 static int __initdata nowait;
109
110 static int __init wait_disable(char *s)
111 {
112 nowait = 1;
113
114 return 1;
115 }
116
117 __setup("nowait", wait_disable);
118
119 void __init check_wait(void)
120 {
121 struct cpuinfo_mips *c = ¤t_cpu_data;
122
123 if (nowait) {
124 printk("Wait instruction disabled.\n");
125 return;
126 }
127
128 /*
129 * MIPSr6 specifies that masked interrupts should unblock an executing
130 * wait instruction, and thus that it is safe for us to use
131 * r4k_wait_irqoff. Yippee!
132 */
133 if (cpu_has_mips_r6) {
134 cpu_wait = r4k_wait_irqoff;
135 return;
136 }
137
138 switch (current_cpu_type()) {
139 case CPU_R3081:
140 case CPU_R3081E:
141 cpu_wait = r3081_wait;
142 break;
143 case CPU_R4200:
144 /* case CPU_R4300: */
145 case CPU_R4600:
146 case CPU_R4640:
147 case CPU_R4650:
148 case CPU_R4700:
149 case CPU_R5000:
150 case CPU_R5500:
151 case CPU_NEVADA:
152 case CPU_4KC:
153 case CPU_4KEC:
154 case CPU_4KSC:
155 case CPU_5KC:
156 case CPU_5KE:
157 case CPU_25KF:
158 case CPU_PR4450:
159 case CPU_BMIPS3300:
160 case CPU_BMIPS4350:
161 case CPU_BMIPS4380:
162 case CPU_CAVIUM_OCTEON:
163 case CPU_CAVIUM_OCTEON_PLUS:
164 case CPU_CAVIUM_OCTEON2:
165 case CPU_CAVIUM_OCTEON3:
166 case CPU_XBURST:
167 case CPU_LOONGSON32:
168 cpu_wait = r4k_wait;
169 break;
170 case CPU_LOONGSON64:
171 if ((c->processor_id & (PRID_IMP_MASK | PRID_REV_MASK)) >=
172 (PRID_IMP_LOONGSON_64C | PRID_REV_LOONGSON3A_R2_0) ||
173 (c->processor_id & PRID_IMP_MASK) == PRID_IMP_LOONGSON_64R)
174 cpu_wait = r4k_wait;
175 break;
176
177 case CPU_BMIPS5000:
178 cpu_wait = r4k_wait_irqoff;
179 break;
180 case CPU_RM7000:
181 cpu_wait = rm7k_wait_irqoff;
182 break;
183
184 case CPU_PROAPTIV:
185 case CPU_P5600:
186 /*
187 * Incoming Fast Debug Channel (FDC) data during a wait
188 * instruction causes the wait never to resume, even if an
189 * interrupt is received. Avoid using wait at all if FDC data is
190 * likely to be received.
191 */
192 if (IS_ENABLED(CONFIG_MIPS_EJTAG_FDC_TTY))
193 break;
194 fallthrough;
195 case CPU_M14KC:
196 case CPU_M14KEC:
197 case CPU_24K:
198 case CPU_34K:
199 case CPU_1004K:
200 case CPU_1074K:
201 case CPU_INTERAPTIV:
202 case CPU_M5150:
203 case CPU_QEMU_GENERIC:
204 cpu_wait = r4k_wait;
205 if (read_c0_config7() & MIPS_CONF7_WII)
206 cpu_wait = r4k_wait_irqoff;
207 break;
208
209 case CPU_74K:
210 cpu_wait = r4k_wait;
211 if ((c->processor_id & 0xff) >= PRID_REV_ENCODE_332(2, 1, 0))
212 cpu_wait = r4k_wait_irqoff;
213 break;
214
215 case CPU_TX49XX:
216 cpu_wait = r4k_wait_irqoff;
217 break;
218 case CPU_ALCHEMY:
219 cpu_wait = au1k_wait;
220 break;
221 case CPU_20KC:
222 /*
223 * WAIT on Rev1.0 has E1, E2, E3 and E16.
224 * WAIT on Rev2.0 and Rev3.0 has E16.
225 * Rev3.1 WAIT is nop, why bother
226 */
227 if ((c->processor_id & 0xff) <= 0x64)
228 break;
229
230 /*
231 * Another rev is incrementing c0_count at a reduced clock
232 * rate while in WAIT mode. So we basically have the choice
233 * between using the cp0 timer as clocksource or avoiding
234 * the WAIT instruction. Until more details are known,
235 * disable the use of WAIT for 20Kc entirely.
236 cpu_wait = r4k_wait;
237 */
238 break;
239 default:
240 break;
241 }
242 }
243
244 __cpuidle void arch_cpu_idle(void)
245 {
246 if (cpu_wait)
247 cpu_wait();
248 }
249
250 #ifdef CONFIG_CPU_IDLE
251
252 __cpuidle int mips_cpuidle_wait_enter(struct cpuidle_device *dev,
253 struct cpuidle_driver *drv, int index)
254 {
255 arch_cpu_idle();
256 return index;
257 }
258
259 #endif
260
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