2 * MIPS idle loop and WAIT instruction support.
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.
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.
14 #include <linux/export.h>
15 #include <linux/init.h>
16 #include <linux/irqflags.h>
17 #include <linux/printk.h>
18 #include <linux/sched.h>
20 #include <asm/cpu-info.h>
21 #include <asm/mipsregs.h>
24 * Not all of the MIPS CPUs have the "wait" instruction available. Moreover,
25 * the implementation of the "wait" feature differs between CPU families. This
26 * points to the function that implements CPU specific wait.
27 * The wait instruction stops the pipeline and reduces the power consumption of
30 void (*cpu_wait)(void);
31 EXPORT_SYMBOL(cpu_wait);
33 static void r3081_wait(void)
35 unsigned long cfg = read_c0_conf();
36 write_c0_conf(cfg | R30XX_CONF_HALT);
39 static void r39xx_wait(void)
43 write_c0_conf(read_c0_conf() | TX39_CONF_HALT);
47 extern void r4k_wait(void);
50 * This variant is preferable as it allows testing need_resched and going to
51 * sleep depending on the outcome atomically. Unfortunately the "It is
52 * implementation-dependent whether the pipeline restarts when a non-enabled
53 * interrupt is requested" restriction in the MIPS32/MIPS64 architecture makes
54 * using this version a gamble.
56 void r4k_wait_irqoff(void)
60 __asm__(" .set push \n"
65 __asm__(" .globl __pastwait \n"
70 * The RM7000 variant has to handle erratum 38. The workaround is to not
71 * have any pending stores when the WAIT instruction is executed.
73 static void rm7k_wait_irqoff(void)
83 " mtc0 $1, $12 # stalls until W stage \n"
85 " mtc0 $1, $12 # stalls until W stage \n"
91 * The Au1xxx wait is available only if using 32khz counter or
92 * external timer source, but specifically not CP0 Counter.
93 * alchemy/common/time.c may override cpu_wait!
95 static void au1k_wait(void)
97 __asm__(" .set mips3 \n"
98 " cache 0x14, 0(%0) \n"
99 " cache 0x14, 32(%0) \n"
108 : : "r" (au1k_wait));
111 static int __initdata nowait;
113 static int __init wait_disable(char *s)
120 __setup("nowait", wait_disable);
122 void __init check_wait(void)
124 struct cpuinfo_mips *c = ¤t_cpu_data;
127 printk("Wait instruction disabled.\n");
131 switch (c->cputype) {
134 cpu_wait = r3081_wait;
137 cpu_wait = r39xx_wait;
140 /* case CPU_R4300: */
158 case CPU_CAVIUM_OCTEON:
159 case CPU_CAVIUM_OCTEON_PLUS:
160 case CPU_CAVIUM_OCTEON2:
169 cpu_wait = rm7k_wait_irqoff;
178 if (read_c0_config7() & MIPS_CONF7_WII)
179 cpu_wait = r4k_wait_irqoff;
184 if ((c->processor_id & 0xff) >= PRID_REV_ENCODE_332(2, 1, 0))
185 cpu_wait = r4k_wait_irqoff;
189 cpu_wait = r4k_wait_irqoff;
192 cpu_wait = au1k_wait;
196 * WAIT on Rev1.0 has E1, E2, E3 and E16.
197 * WAIT on Rev2.0 and Rev3.0 has E16.
198 * Rev3.1 WAIT is nop, why bother
200 if ((c->processor_id & 0xff) <= 0x64)
204 * Another rev is incremeting c0_count at a reduced clock
205 * rate while in WAIT mode. So we basically have the choice
206 * between using the cp0 timer as clocksource or avoiding
207 * the WAIT instruction. Until more details are known,
208 * disable the use of WAIT for 20Kc entirely.
213 if ((c->processor_id & 0x00ff) >= 0x40)
221 static void smtc_idle_hook(void)
223 #ifdef CONFIG_MIPS_MT_SMTC
224 void smtc_idle_loop_hook(void);
226 smtc_idle_loop_hook();
230 void arch_cpu_idle(void)