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Diffstat (limited to 'arch/mips/kernel/idle.c')
| -rw-r--r-- | arch/mips/kernel/idle.c | 256 |
1 files changed, 256 insertions, 0 deletions
diff --git a/arch/mips/kernel/idle.c b/arch/mips/kernel/idle.c new file mode 100644 index 000000000..e4f62b787 --- /dev/null +++ b/arch/mips/kernel/idle.c @@ -0,0 +1,256 @@ +/* + * MIPS idle loop and WAIT instruction support. + * + * Copyright (C) xxxx the Anonymous + * Copyright (C) 1994 - 2006 Ralf Baechle + * Copyright (C) 2003, 2004 Maciej W. Rozycki + * Copyright (C) 2001, 2004, 2011, 2012 MIPS Technologies, Inc. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ +#include <linux/export.h> +#include <linux/init.h> +#include <linux/irqflags.h> +#include <linux/printk.h> +#include <linux/sched.h> +#include <asm/cpu.h> +#include <asm/cpu-info.h> +#include <asm/cpu-type.h> +#include <asm/idle.h> +#include <asm/mipsregs.h> + +/* + * Not all of the MIPS CPUs have the "wait" instruction available. Moreover, + * the implementation of the "wait" feature differs between CPU families. This + * points to the function that implements CPU specific wait. + * The wait instruction stops the pipeline and reduces the power consumption of + * the CPU very much. + */ +void (*cpu_wait)(void); +EXPORT_SYMBOL(cpu_wait); + +static void r3081_wait(void) +{ + unsigned long cfg = read_c0_conf(); + write_c0_conf(cfg | R30XX_CONF_HALT); + local_irq_enable(); +} + +static void r39xx_wait(void) +{ + if (!need_resched()) + write_c0_conf(read_c0_conf() | TX39_CONF_HALT); + local_irq_enable(); +} + +void r4k_wait(void) +{ + local_irq_enable(); + __r4k_wait(); +} + +/* + * This variant is preferable as it allows testing need_resched and going to + * sleep depending on the outcome atomically. Unfortunately the "It is + * implementation-dependent whether the pipeline restarts when a non-enabled + * interrupt is requested" restriction in the MIPS32/MIPS64 architecture makes + * using this version a gamble. + */ +void r4k_wait_irqoff(void) +{ + if (!need_resched()) + __asm__( + " .set push \n" + " .set arch=r4000 \n" + " wait \n" + " .set pop \n"); + local_irq_enable(); +} + +/* + * The RM7000 variant has to handle erratum 38. The workaround is to not + * have any pending stores when the WAIT instruction is executed. + */ +static void rm7k_wait_irqoff(void) +{ + if (!need_resched()) + __asm__( + " .set push \n" + " .set arch=r4000 \n" + " .set noat \n" + " mfc0 $1, $12 \n" + " sync \n" + " mtc0 $1, $12 # stalls until W stage \n" + " wait \n" + " mtc0 $1, $12 # stalls until W stage \n" + " .set pop \n"); + local_irq_enable(); +} + +/* + * Au1 'wait' is only useful when the 32kHz counter is used as timer, + * since coreclock (and the cp0 counter) stops upon executing it. Only an + * interrupt can wake it, so they must be enabled before entering idle modes. + */ +static void au1k_wait(void) +{ + unsigned long c0status = read_c0_status() | 1; /* irqs on */ + + __asm__( + " .set arch=r4000 \n" + " cache 0x14, 0(%0) \n" + " cache 0x14, 32(%0) \n" + " sync \n" + " mtc0 %1, $12 \n" /* wr c0status */ + " wait \n" + " nop \n" + " nop \n" + " nop \n" + " nop \n" + " .set mips0 \n" + : : "r" (au1k_wait), "r" (c0status)); +} + +static int __initdata nowait; + +static int __init wait_disable(char *s) +{ + nowait = 1; + + return 1; +} + +__setup("nowait", wait_disable); + +void __init check_wait(void) +{ + struct cpuinfo_mips *c = ¤t_cpu_data; + + if (nowait) { + printk("Wait instruction disabled.\n"); + return; + } + + switch (current_cpu_type()) { + case CPU_R3081: + case CPU_R3081E: + cpu_wait = r3081_wait; + break; + case CPU_TX3927: + cpu_wait = r39xx_wait; + break; + case CPU_R4200: +/* case CPU_R4300: */ + case CPU_R4600: + case CPU_R4640: + case CPU_R4650: + case CPU_R4700: + case CPU_R5000: + case CPU_R5500: + case CPU_NEVADA: + case CPU_4KC: + case CPU_4KEC: + case CPU_4KSC: + case CPU_5KC: + case CPU_25KF: + case CPU_PR4450: + case CPU_BMIPS3300: + case CPU_BMIPS4350: + case CPU_BMIPS4380: + case CPU_BMIPS5000: + case CPU_CAVIUM_OCTEON: + case CPU_CAVIUM_OCTEON_PLUS: + case CPU_CAVIUM_OCTEON2: + case CPU_CAVIUM_OCTEON3: + case CPU_JZRISC: + case CPU_LOONGSON1: + case CPU_XLR: + case CPU_XLP: + cpu_wait = r4k_wait; + break; + + case CPU_RM7000: + cpu_wait = rm7k_wait_irqoff; + break; + + case CPU_PROAPTIV: + case CPU_P5600: + /* + * Incoming Fast Debug Channel (FDC) data during a wait + * instruction causes the wait never to resume, even if an + * interrupt is received. Avoid using wait at all if FDC data is + * likely to be received. + */ + if (IS_ENABLED(CONFIG_MIPS_EJTAG_FDC_TTY)) + break; + /* fall through */ + case CPU_M14KC: + case CPU_M14KEC: + case CPU_24K: + case CPU_34K: + case CPU_1004K: + case CPU_1074K: + case CPU_INTERAPTIV: + case CPU_M5150: + case CPU_QEMU_GENERIC: + cpu_wait = r4k_wait; + if (read_c0_config7() & MIPS_CONF7_WII) + cpu_wait = r4k_wait_irqoff; + break; + + case CPU_74K: + cpu_wait = r4k_wait; + if ((c->processor_id & 0xff) >= PRID_REV_ENCODE_332(2, 1, 0)) + cpu_wait = r4k_wait_irqoff; + break; + + case CPU_TX49XX: + cpu_wait = r4k_wait_irqoff; + break; + case CPU_ALCHEMY: + cpu_wait = au1k_wait; + break; + case CPU_20KC: + /* + * WAIT on Rev1.0 has E1, E2, E3 and E16. + * WAIT on Rev2.0 and Rev3.0 has E16. + * Rev3.1 WAIT is nop, why bother + */ + if ((c->processor_id & 0xff) <= 0x64) + break; + + /* + * Another rev is incremeting c0_count at a reduced clock + * rate while in WAIT mode. So we basically have the choice + * between using the cp0 timer as clocksource or avoiding + * the WAIT instruction. Until more details are known, + * disable the use of WAIT for 20Kc entirely. + cpu_wait = r4k_wait; + */ + break; + default: + break; + } +} + +void arch_cpu_idle(void) +{ + if (cpu_wait) + cpu_wait(); + else + local_irq_enable(); +} + +#ifdef CONFIG_CPU_IDLE + +int mips_cpuidle_wait_enter(struct cpuidle_device *dev, + struct cpuidle_driver *drv, int index) +{ + arch_cpu_idle(); + return index; +} + +#endif |