/*
* Copyright 2010 Tilera Corporation. All Rights Reserved.
*
* 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, version 2.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
* NON INFRINGEMENT. See the GNU General Public License for
* more details.
*
* Support the cycle counter clocksource and tile timer clock event device.
*/
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/hardirq.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/delay.h>
#include <asm/irq_regs.h>
#include <asm/traps.h>
#include <hv/hypervisor.h>
#include <arch/interrupts.h>
#include <arch/spr_def.h>
/*
* Define the cycle counter clock source.
*/
/* How many cycles per second we are running at. */
static cycles_t cycles_per_sec __write_once;
cycles_t get_clock_rate(void)
{
return cycles_per_sec;
}
#if CHIP_HAS_SPLIT_CYCLE()
cycles_t get_cycles(void)
{
unsigned int high = __insn_mfspr(SPR_CYCLE_HIGH);
unsigned int low = __insn_mfspr(SPR_CYCLE_LOW);
unsigned int high2 = __insn_mfspr(SPR_CYCLE_HIGH);
while (unlikely(high != high2)) {
low = __insn_mfspr(SPR_CYCLE_LOW);
high = high2;
high2 = __insn_mfspr(SPR_CYCLE_HIGH);
}
return (((cycles_t)high) << 32) | low;
}
#endif
/*
* We use a relatively small shift value so that sched_clock()
* won't wrap around very often.
*/
#define SCHED_CLOCK_SHIFT 10
static unsigned long sched_clock_mult __write_once;
static cycles_t clocksource_get_cycles(struct clocksource *cs)
{
return get_cycles();
}
static struct clocksource cycle_counter_cs = {
.name = "cycle counter",
.rating = 300,
.read = clocksource_get_cycles,
.mask = CLOCKSOURCE_MASK(64),
.shift = 22, /* typical value, e.g. x86 tsc uses this */
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
/*
* Called very early from setup_arch() to set cycles_per_sec.
* We initialize it early so we can use it to set up loops_per_jiffy.
*/
void __init setup_clock(void)
{
cycles_per_sec = hv_sysconf(HV_SYSCONF_CPU_SPEED);
sched_clock_mult =
clocksource_hz2mult(cycles_per_sec, SCHED_CLOCK_SHIFT);
cycle_counter_cs.mult =
clocksource_hz2mult(cycles_per_sec, cycle_counter_cs.shift);
}
void __init calibrate_delay(void)
{
loops_per_jiffy = get_clock_rate() / HZ;
pr_info("Clock rate yields %lu.%02lu BogoMIPS (lpj=%lu)\n",
loops_per_jiffy/(500000/HZ),
(loops_per_jiffy/(5000/HZ)) % 100, loops_per_jiffy);
}
/* Called fairly late in init/main.c, but before we go smp. */
void __init time_init(void)
{
/* Initialize and register the clock source. */
clocksource_register(&cycle_counter_cs);
/* Start up the tile-timer interrupt source on the boot cpu. */
setup_tile_timer();
}
/*
* Define the tile timer clock event device. The timer is driven by
* the TILE_TIMER_CONTROL register, which consists of a 31-bit down
* counter, plus bit 31, which signifies that the counter has wrapped
* from zero to (2**31) - 1. The INT_TILE_TIMER interrupt will be
* raised as long as bit 31 is set.
*
* The TILE_MINSEC value represents the largest range of real-time
* we can possibly cover with the timer, based on MAX_TICK combined
* with the slowest reasonable clock rate we might run at.
*/
#define MAX_TICK 0x7fffffff /* we have 31 bits of countdown timer */
#define TILE_MINSEC 5 /* timer covers no more than 5 seconds */
static int tile_timer_set_next_event(unsigned long ticks,
struct clock_event_device *evt)
{
BUG_ON(ticks > MAX_TICK);
__insn_mtspr(SPR_TILE_TIMER_CONTROL, ticks);
arch_local_irq_unmask_now(INT_TILE_TIMER);
return 0;
}
/*
* Whenever anyone tries to change modes, we just mask interrupts
* and wait for the next event to get set.
*/
static void tile_timer_set_mode(enum clock_event_mode mode,
struct clock_event_device *evt)
{
arch_local_irq_mask_now(INT_TILE_TIMER);
}
/*
* Set min_delta_ns to 1 microsecond, since it takes about
* that long to fire the interrupt.
*/
static DEFINE_PER_CPU(struct clock_event_device, tile_timer) = {
.name = "tile timer",
.features = CLOCK_EVT_FEAT_ONESHOT,
.min_delta_ns = 1000,
.rating = 100,
.irq = -1,
.set_next_event = tile_timer_set_next_event,
.set_mode = tile_timer_set_mode,
};
void __cpuinit setup_tile_timer(void)
{
struct clock_event_device *evt = &__get_cpu_var(tile_timer);
/* Fill in fields that are speed-specific. */
clockevents_calc_mult_shift(evt, cycles_per_sec, TILE_MINSEC);
evt->max_delta_ns = clockevent_delta2ns(MAX_TICK, evt);
/* Mark as being for this cpu only. */
evt->cpumask = cpumask_of(smp_processor_id());
/* Start out with timer not firing. */
arch_local_irq_mask_now(INT_TILE_TIMER);
/* Register tile timer. */
clockevents_register_device(evt);
}
/* Called from the interrupt vector. */
void do_timer_interrupt(struct pt_regs *regs, int fault_num)
{
struct pt_regs *old_regs = set_irq_regs(regs);
struct clock_event_device *evt = &__get_cpu_var(tile_timer);
/*
* Mask the timer interrupt here, since we are a oneshot timer
* and there are now by definition no events pending.
*/
arch_local_irq_mask(INT_TILE_TIMER);
/* Track time spent here in an interrupt context */
irq_enter();
/* Track interrupt count. */
__get_cpu_var(irq_stat).irq_timer_count++;
/* Call the generic timer handler */
evt->event_handler(evt);
/*
* Track time spent against the current process again and
* process any softirqs if they are waiting.
*/
irq_exit();
set_irq_regs(old_regs);
}
/*
* Scheduler clock - returns current time in nanosec units.
* Note that with LOCKDEP, this is called during lockdep_init(), and
* we will claim that sched_clock() is zero for a little while, until
* we run setup_clock(), above.
*/
unsigned long long sched_clock(void)
{
return clocksource_cyc2ns(get_cycles(),
sched_clock_mult, SCHED_CLOCK_SHIFT);
}
int setup_profiling_timer(unsigned int multiplier)
{
return -EINVAL;
}
/*
* Use the tile timer to convert nsecs to core clock cycles, relying
* on it having the same frequency as SPR_CYCLE.
*/
cycles_t ns2cycles(unsigned long nsecs)
{
struct clock_event_device *dev = &__get_cpu_var(tile_timer);
return ((u64)nsecs * dev->mult) >> dev->shift;
}
