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linux/arch/mips/kernel/time.c

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/*
* Copyright 2001 MontaVista Software Inc.
* Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
* Copyright (c) 2003, 2004 Maciej W. Rozycki
*
* Common time service routines for MIPS machines. See
* Documentation/mips/time.README.
*
* 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/bug.h>
#include <linux/clockchips.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/param.h>
#include <linux/profile.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/smp.h>
#include <linux/kernel_stat.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <asm/bootinfo.h>
#include <asm/cache.h>
#include <asm/compiler.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
#include <asm/div64.h>
#include <asm/sections.h>
#include <asm/smtc_ipi.h>
#include <asm/time.h>
#include <irq.h>
/*
* forward reference
*/
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);
int __weak rtc_mips_set_time(unsigned long sec)
{
return 0;
}
EXPORT_SYMBOL(rtc_mips_set_time);
int __weak rtc_mips_set_mmss(unsigned long nowtime)
{
return rtc_mips_set_time(nowtime);
}
int update_persistent_clock(struct timespec now)
{
return rtc_mips_set_mmss(now.tv_sec);
}
/*
* Null high precision timer functions for systems lacking one.
*/
static cycle_t null_hpt_read(void)
{
return 0;
}
/*
* High precision timer functions for a R4k-compatible timer.
*/
static cycle_t c0_hpt_read(void)
{
return read_c0_count();
}
int (*mips_timer_state)(void);
IRQ: Maintain regs pointer globally rather than passing to IRQ handlers Maintain a per-CPU global "struct pt_regs *" variable which can be used instead of passing regs around manually through all ~1800 interrupt handlers in the Linux kernel. The regs pointer is used in few places, but it potentially costs both stack space and code to pass it around. On the FRV arch, removing the regs parameter from all the genirq function results in a 20% speed up of the IRQ exit path (ie: from leaving timer_interrupt() to leaving do_IRQ()). Where appropriate, an arch may override the generic storage facility and do something different with the variable. On FRV, for instance, the address is maintained in GR28 at all times inside the kernel as part of general exception handling. Having looked over the code, it appears that the parameter may be handed down through up to twenty or so layers of functions. Consider a USB character device attached to a USB hub, attached to a USB controller that posts its interrupts through a cascaded auxiliary interrupt controller. A character device driver may want to pass regs to the sysrq handler through the input layer which adds another few layers of parameter passing. I've build this code with allyesconfig for x86_64 and i386. I've runtested the main part of the code on FRV and i386, though I can't test most of the drivers. I've also done partial conversion for powerpc and MIPS - these at least compile with minimal configurations. This will affect all archs. Mostly the changes should be relatively easy. Take do_IRQ(), store the regs pointer at the beginning, saving the old one: struct pt_regs *old_regs = set_irq_regs(regs); And put the old one back at the end: set_irq_regs(old_regs); Don't pass regs through to generic_handle_irq() or __do_IRQ(). In timer_interrupt(), this sort of change will be necessary: - update_process_times(user_mode(regs)); - profile_tick(CPU_PROFILING, regs); + update_process_times(user_mode(get_irq_regs())); + profile_tick(CPU_PROFILING); I'd like to move update_process_times()'s use of get_irq_regs() into itself, except that i386, alone of the archs, uses something other than user_mode(). Some notes on the interrupt handling in the drivers: (*) input_dev() is now gone entirely. The regs pointer is no longer stored in the input_dev struct. (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking. It does something different depending on whether it's been supplied with a regs pointer or not. (*) Various IRQ handler function pointers have been moved to type irq_handler_t. Signed-Off-By: David Howells <dhowells@redhat.com> (cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
2006-10-05 06:55:46 -07:00
int null_perf_irq(void)
{
return 0;
}
EXPORT_SYMBOL(null_perf_irq);
IRQ: Maintain regs pointer globally rather than passing to IRQ handlers Maintain a per-CPU global "struct pt_regs *" variable which can be used instead of passing regs around manually through all ~1800 interrupt handlers in the Linux kernel. The regs pointer is used in few places, but it potentially costs both stack space and code to pass it around. On the FRV arch, removing the regs parameter from all the genirq function results in a 20% speed up of the IRQ exit path (ie: from leaving timer_interrupt() to leaving do_IRQ()). Where appropriate, an arch may override the generic storage facility and do something different with the variable. On FRV, for instance, the address is maintained in GR28 at all times inside the kernel as part of general exception handling. Having looked over the code, it appears that the parameter may be handed down through up to twenty or so layers of functions. Consider a USB character device attached to a USB hub, attached to a USB controller that posts its interrupts through a cascaded auxiliary interrupt controller. A character device driver may want to pass regs to the sysrq handler through the input layer which adds another few layers of parameter passing. I've build this code with allyesconfig for x86_64 and i386. I've runtested the main part of the code on FRV and i386, though I can't test most of the drivers. I've also done partial conversion for powerpc and MIPS - these at least compile with minimal configurations. This will affect all archs. Mostly the changes should be relatively easy. Take do_IRQ(), store the regs pointer at the beginning, saving the old one: struct pt_regs *old_regs = set_irq_regs(regs); And put the old one back at the end: set_irq_regs(old_regs); Don't pass regs through to generic_handle_irq() or __do_IRQ(). In timer_interrupt(), this sort of change will be necessary: - update_process_times(user_mode(regs)); - profile_tick(CPU_PROFILING, regs); + update_process_times(user_mode(get_irq_regs())); + profile_tick(CPU_PROFILING); I'd like to move update_process_times()'s use of get_irq_regs() into itself, except that i386, alone of the archs, uses something other than user_mode(). Some notes on the interrupt handling in the drivers: (*) input_dev() is now gone entirely. The regs pointer is no longer stored in the input_dev struct. (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking. It does something different depending on whether it's been supplied with a regs pointer or not. (*) Various IRQ handler function pointers have been moved to type irq_handler_t. Signed-Off-By: David Howells <dhowells@redhat.com> (cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)
2006-10-05 06:55:46 -07:00
int (*perf_irq)(void) = null_perf_irq;
EXPORT_SYMBOL(perf_irq);
/*
* time_init() - it does the following things.
*
* 1) plat_time_init() -
* a) (optional) set up RTC routines,
* b) (optional) calibrate and set the mips_hpt_frequency
* (only needed if you intended to use cpu counter as timer interrupt
* source)
* 2) calculate a couple of cached variables for later usage
*/
unsigned int mips_hpt_frequency;
static unsigned int __init calibrate_hpt(void)
{
cycle_t frequency, hpt_start, hpt_end, hpt_count, hz;
const int loops = HZ / 10;
int log_2_loops = 0;
int i;
/*
* We want to calibrate for 0.1s, but to avoid a 64-bit
* division we round the number of loops up to the nearest
* power of 2.
*/
while (loops > 1 << log_2_loops)
log_2_loops++;
i = 1 << log_2_loops;
/*
* Wait for a rising edge of the timer interrupt.
*/
while (mips_timer_state());
while (!mips_timer_state());
/*
* Now see how many high precision timer ticks happen
* during the calculated number of periods between timer
* interrupts.
*/
hpt_start = clocksource_mips.read();
do {
while (mips_timer_state());
while (!mips_timer_state());
} while (--i);
hpt_end = clocksource_mips.read();
hpt_count = (hpt_end - hpt_start) & clocksource_mips.mask;
hz = HZ;
frequency = hpt_count * hz;
return frequency >> log_2_loops;
}
struct clocksource clocksource_mips = {
.name = "MIPS",
.mask = CLOCKSOURCE_MASK(32),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
void __init clocksource_set_clock(struct clocksource *cs, unsigned int clock)
{
u64 temp;
u32 shift;
/* Find a shift value */
for (shift = 32; shift > 0; shift--) {
temp = (u64) NSEC_PER_SEC << shift;
do_div(temp, clock);
if ((temp >> 32) == 0)
break;
}
cs->shift = shift;
cs->mult = (u32) temp;
}
void __cpuinit clockevent_set_clock(struct clock_event_device *cd,
unsigned int clock)
{
u64 temp;
u32 shift;
/* Find a shift value */
for (shift = 32; shift > 0; shift--) {
temp = (u64) clock << shift;
do_div(temp, NSEC_PER_SEC);
if ((temp >> 32) == 0)
break;
}
cd->shift = shift;
cd->mult = (u32) temp;
}
static void __init init_mips_clocksource(void)
{
if (!mips_hpt_frequency || clocksource_mips.read == null_hpt_read)
return;
/* Calclate a somewhat reasonable rating value */
clocksource_mips.rating = 200 + mips_hpt_frequency / 10000000;
clocksource_set_clock(&clocksource_mips, mips_hpt_frequency);
clocksource_register(&clocksource_mips);
}
void __init __weak plat_time_init(void)
{
}
/*
* This function exists in order to cause an error due to a duplicate
* definition if platform code should have its own implementation. The hook
* to use instead is plat_time_init. plat_time_init does not receive the
* irqaction pointer argument anymore. This is because any function which
* initializes an interrupt timer now takes care of its own request_irq rsp.
* setup_irq calls and each clock_event_device should use its own
* struct irqrequest.
*/
void __init plat_timer_setup(struct irqaction *irq)
{
BUG();
}
void __init time_init(void)
{
plat_time_init();
/* Choose appropriate high precision timer routines. */
if (!cpu_has_counter && !clocksource_mips.read)
/* No high precision timer -- sorry. */
clocksource_mips.read = null_hpt_read;
else if (!mips_hpt_frequency && !mips_timer_state) {
/* A high precision timer of unknown frequency. */
if (!clocksource_mips.read)
/* No external high precision timer -- use R4k. */
clocksource_mips.read = c0_hpt_read;
} else {
/* We know counter frequency. Or we can get it. */
if (!clocksource_mips.read) {
/* No external high precision timer -- use R4k. */
clocksource_mips.read = c0_hpt_read;
}
if (!mips_hpt_frequency)
mips_hpt_frequency = calibrate_hpt();
/* Report the high precision timer rate for a reference. */
printk("Using %u.%03u MHz high precision timer.\n",
((mips_hpt_frequency + 500) / 1000) / 1000,
((mips_hpt_frequency + 500) / 1000) % 1000);
}
init_mips_clocksource();
mips_clockevent_init();
}