/*
* 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;
}
/*
* MIPSr6 specifies that masked interrupts should unblock an executing
* wait instruction, and thus that it is safe for us to use
* r4k_wait_irqoff. Yippee!
*/
if (cpu_has_mips_r6) {
cpu_wait = r4k_wait_irqoff;
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_5KE:
case CPU_25KF:
case CPU_PR4450:
case CPU_BMIPS3300:
case CPU_BMIPS4350:
case CPU_BMIPS4380:
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_BMIPS5000:
cpu_wait = r4k_wait_irqoff;
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