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ARC: Timers/counters/delay management

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ARC700 includes 2 in-core 32bit timers TIMER0 and TIMER1.
Both have exactly same capabilies.

* programmable to count from TIMER<n>_CNT to TIMER<n>_LIMIT
* for count 0 and LIMIT ~1, provides a free-running counter by
    auto-wrapping when limit is reached.
* optionally interrupt when LIMIT is reached (oneshot event semantics)
* rearming the interrupt provides periodic semantics
* run at CPU clk

ARC Linux uses TIMER0 for clockevent (periodic/oneshot) and TIMER1 for
clocksource (free-running clock).

Newer cores provide RTSC insn which gives a 64bit cpu clk snapshot hence
is more apt for clocksource when available.

SMP poses a bit of challenge for global timekeeping clocksource /
sched_clock() backend:
 -TIMER1 based local clocks are out-of-sync hence can't be used
  (thus we default to jiffies based cs as well as sched_clock() one/both
  of which platform can override with it's specific hardware assist)
 -RTSC is only allowed in SMP if it's cross-core-sync (Kconfig glue
  ensures that) and thus usable for both requirements.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Vineet Gupta 2013-01-18 15:12:18 +05:30
parent bf90e1eab6
commit d8005e6b95
7 changed files with 425 additions and 0 deletions
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11
arch/arc/include/asm/arcregs.h
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@ -47,6 +47,17 @@
#define AUX_ITRIGGER 0x40d
#define AUX_IPULSE 0x415
/* Timer related Aux registers */
#define ARC_REG_TIMER0_LIMIT 0x23 /* timer 0 limit */
#define ARC_REG_TIMER0_CTRL 0x22 /* timer 0 control */
#define ARC_REG_TIMER0_CNT 0x21 /* timer 0 count */
#define ARC_REG_TIMER1_LIMIT 0x102 /* timer 1 limit */
#define ARC_REG_TIMER1_CTRL 0x101 /* timer 1 control */
#define ARC_REG_TIMER1_CNT 0x100 /* timer 1 count */
#define TIMER_CTRL_IE (1 << 0) /* Interupt when Count reachs limit */
#define TIMER_CTRL_NH (1 << 1) /* Count only when CPU NOT halted */
/*
* Floating Pt Registers
* Status regs are read-only (build-time) so need not be saved/restored

20
arch/arc/include/asm/clk.h Normal file
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@ -0,0 +1,20 @@
/*
* Copyright (C) 2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef _ASM_ARC_CLK_H
#define _ASM_ARC_CLK_H
/* Although we can't really hide core_freq, the accessor is still better way */
extern unsigned long core_freq;
static inline unsigned long arc_get_core_freq(void)
{
return core_freq;
}
#endif

68
arch/arc/include/asm/delay.h Normal file
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@ -0,0 +1,68 @@
/*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Delay routines using pre computed loops_per_jiffy value.
*
* vineetg: Feb 2012
* -Rewrote in "C" to avoid dealing with availability of H/w MPY
* -Also reduced the num of MPY operations from 3 to 2
*
* Amit Bhor: Codito Technologies 2004
*/
#ifndef __ASM_ARC_UDELAY_H
#define __ASM_ARC_UDELAY_H
#include <asm/param.h> /* HZ */
static inline void __delay(unsigned long loops)
{
__asm__ __volatile__(
"1: sub.f %0, %0, 1 \n"
" jpnz 1b \n"
: "+r"(loops)
:
: "cc");
}
extern void __bad_udelay(void);
/*
* Normal Math for computing loops in "N" usecs
* -we have precomputed @loops_per_jiffy
* -1 sec has HZ jiffies
* loops per "N" usecs = ((loops_per_jiffy * HZ / 1000000) * N)
*
* Approximate Division by multiplication:
* -Mathematically if we multiply and divide a number by same value the
* result remains unchanged: In this case, we use 2^32
* -> (loops_per_N_usec * 2^32 ) / 2^32
* -> (((loops_per_jiffy * HZ / 1000000) * N) * 2^32) / 2^32
* -> (loops_per_jiffy * HZ * N * 4295) / 2^32
*
* -Divide by 2^32 is very simply right shift by 32
* -We simply need to ensure that the multiply per above eqn happens in
* 64-bit precision (if CPU doesn't support it - gcc can emaulate it)
*/
static inline void __udelay(unsigned long usecs)
{
unsigned long loops;
/* (long long) cast ensures 64 bit MPY - real or emulated
* HZ * 4295 is pre-evaluated by gcc - hence only 2 mpy ops
*/
loops = ((long long)(usecs * 4295 * HZ) *
(long long)(loops_per_jiffy)) >> 32;
__delay(loops);
}
#define udelay(n) (__builtin_constant_p(n) ? ((n) > 20000 ? __bad_udelay() \
: __udelay(n)) : __udelay(n))
#endif /* __ASM_ARC_UDELAY_H */

2
arch/arc/include/asm/irq.h
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@ -19,4 +19,6 @@ extern void __init arc_init_IRQ(void);
extern void __init plat_init_IRQ(void);
extern int __init get_hw_config_num_irq(void);
void __cpuinit arc_local_timer_setup(unsigned int cpu);
#endif

18
arch/arc/include/asm/timex.h Normal file
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@ -0,0 +1,18 @@
/*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef _ASM_ARC_TIMEX_H
#define _ASM_ARC_TIMEX_H
#define CLOCK_TICK_RATE 80000000 /* slated to be removed */
#include <asm-generic/timex.h>
/* XXX: get_cycles() to be implemented with RTSC insn */
#endif /* _ASM_ARC_TIMEX_H */

11
arch/arc/kernel/clk.c Normal file
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@ -0,0 +1,11 @@
/*
* Copyright (C) 2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <asm/clk.h>
unsigned long core_freq = CONFIG_ARC_PLAT_CLK;

295
arch/arc/kernel/time.c Normal file
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@ -0,0 +1,295 @@
/*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* vineetg: Jan 1011
* -sched_clock( ) no longer jiffies based. Uses the same clocksource
* as gtod
*
* Rajeshwarr/Vineetg: Mar 2008
* -Implemented CONFIG_GENERIC_TIME (rather deleted arch specific code)
* for arch independent gettimeofday()
* -Implemented CONFIG_GENERIC_CLOCKEVENTS as base for hrtimers
*
* Vineetg: Mar 2008: Forked off from time.c which now is time-jiff.c
*/
/* ARC700 has two 32bit independent prog Timers: TIMER0 and TIMER1
* Each can programmed to go from @count to @limit and optionally
* interrupt when that happens.
* A write to Control Register clears the Interrupt
*
* We've designated TIMER0 for events (clockevents)
* while TIMER1 for free running (clocksource)
*
* Newer ARC700 cores have 64bit clk fetching RTSC insn, preferred over TIMER1
*/
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/timex.h>
#include <linux/profile.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <asm/irq.h>
#include <asm/arcregs.h>
#include <asm/clk.h>
#define ARC_TIMER_MAX 0xFFFFFFFF
/********** Clock Source Device *********/
#ifdef CONFIG_ARC_HAS_RTSC
int __cpuinit arc_counter_setup(void)
{
/* RTSC insn taps into cpu clk, needs no setup */
/* For SMP, only allowed if cross-core-sync, hence usable as cs */
return 1;
}
static cycle_t arc_counter_read(struct clocksource *cs)
{
unsigned long flags;
union {
#ifdef CONFIG_CPU_BIG_ENDIAN
struct { u32 high, low; };
#else
struct { u32 low, high; };
#endif
cycle_t full;
} stamp;
flags = arch_local_irq_save();
__asm__ __volatile(
" .extCoreRegister tsch, 58, r, cannot_shortcut \n"
" rtsc %0, 0 \n"
" mov %1, tsch \n" /* TSCH is extn core reg 58 */
: "=r" (stamp.low), "=r" (stamp.high));
arch_local_irq_restore(flags);
return stamp.full;
}
static struct clocksource arc_counter = {
.name = "ARC RTSC",
.rating = 300,
.read = arc_counter_read,
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
#else /* !CONFIG_ARC_HAS_RTSC */
static bool is_usable_as_clocksource(void)
{
#ifdef CONFIG_SMP
return 0;
#else
return 1;
#endif
}
/*
* set 32bit TIMER1 to keep counting monotonically and wraparound
*/
int __cpuinit arc_counter_setup(void)
{
write_aux_reg(ARC_REG_TIMER1_LIMIT, ARC_TIMER_MAX);
write_aux_reg(ARC_REG_TIMER1_CNT, 0);
write_aux_reg(ARC_REG_TIMER1_CTRL, TIMER_CTRL_NH);
return is_usable_as_clocksource();
}
static cycle_t arc_counter_read(struct clocksource *cs)
{
return (cycle_t) read_aux_reg(ARC_REG_TIMER1_CNT);
}
static struct clocksource arc_counter = {
.name = "ARC Timer1",
.rating = 300,
.read = arc_counter_read,
.mask = CLOCKSOURCE_MASK(32),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
#endif
/********** Clock Event Device *********/
/*
* Arm the timer to interrupt after @limit cycles
* The distinction for oneshot/periodic is done in arc_event_timer_ack() below
*/
static void arc_timer_event_setup(unsigned int limit)
{
write_aux_reg(ARC_REG_TIMER0_LIMIT, limit);
write_aux_reg(ARC_REG_TIMER0_CNT, 0); /* start from 0 */
write_aux_reg(ARC_REG_TIMER0_CTRL, TIMER_CTRL_IE | TIMER_CTRL_NH);
}
/*
* Acknowledge the interrupt (oneshot) and optionally re-arm it (periodic)
* -Any write to CTRL Reg will ack the intr (NH bit: Count when not halted)
* -Rearming is done by setting the IE bit
*
* Small optimisation: Normal code would have been
* if (irq_reenable)
* CTRL_REG = (IE | NH);
* else
* CTRL_REG = NH;
* However since IE is BIT0 we can fold the branch
*/
static void arc_timer_event_ack(unsigned int irq_reenable)
{
write_aux_reg(ARC_REG_TIMER0_CTRL, irq_reenable | TIMER_CTRL_NH);
}
static int arc_clkevent_set_next_event(unsigned long delta,
struct clock_event_device *dev)
{
arc_timer_event_setup(delta);
return 0;
}
static void arc_clkevent_set_mode(enum clock_event_mode mode,
struct clock_event_device *dev)
{
switch (mode) {
case CLOCK_EVT_MODE_PERIODIC:
arc_timer_event_setup(arc_get_core_freq() / HZ);
break;
case CLOCK_EVT_MODE_ONESHOT:
break;
default:
break;
}
return;
}
static DEFINE_PER_CPU(struct clock_event_device, arc_clockevent_device) = {
.name = "ARC Timer0",
.features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
.mode = CLOCK_EVT_MODE_UNUSED,
.rating = 300,
.irq = TIMER0_IRQ, /* hardwired, no need for resources */
.set_next_event = arc_clkevent_set_next_event,
.set_mode = arc_clkevent_set_mode,
};
static irqreturn_t timer_irq_handler(int irq, void *dev_id)
{
struct clock_event_device *clk = &__get_cpu_var(arc_clockevent_device);
arc_timer_event_ack(clk->mode == CLOCK_EVT_MODE_PERIODIC);
clk->event_handler(clk);
return IRQ_HANDLED;
}
static struct irqaction arc_timer_irq = {
.name = "Timer0 (clock-evt-dev)",
.flags = IRQF_TIMER | IRQF_PERCPU,
.handler = timer_irq_handler,
};
/*
* Setup the local event timer for @cpu
* N.B. weak so that some exotic ARC SoCs can completely override it
*/
void __attribute__((weak)) __cpuinit arc_local_timer_setup(unsigned int cpu)
{
struct clock_event_device *clk = &per_cpu(arc_clockevent_device, cpu);
clockevents_calc_mult_shift(clk, arc_get_core_freq(), 5);
clk->max_delta_ns = clockevent_delta2ns(ARC_TIMER_MAX, clk);
clk->cpumask = cpumask_of(cpu);
clockevents_register_device(clk);
/*
* setup the per-cpu timer IRQ handler - for all cpus
* For non boot CPU explicitly unmask at intc
* setup_irq() -> .. -> irq_startup() already does this on boot-cpu
*/
if (!cpu)
setup_irq(TIMER0_IRQ, &arc_timer_irq);
else
arch_unmask_irq(TIMER0_IRQ);
}
/*
* Called from start_kernel() - boot CPU only
*
* -Sets up h/w timers as applicable on boot cpu
* -Also sets up any global state needed for timer subsystem:
* - for "counting" timer, registers a clocksource, usable across CPUs
* (provided that underlying counter h/w is synchronized across cores)
* - for "event" timer, sets up TIMER0 IRQ (as that is platform agnostic)
*/
void __init time_init(void)
{
/*
* sets up the timekeeping free-flowing counter which also returns
* whether the counter is usable as clocksource
*/
if (arc_counter_setup())
/*
* CLK upto 4.29 GHz can be safely represented in 32 bits
* because Max 32 bit number is 4,294,967,295
*/
clocksource_register_hz(&arc_counter, arc_get_core_freq());
/* sets up the periodic event timer */
arc_local_timer_setup(smp_processor_id());
}
#ifdef CONFIG_ARC_HAS_RTSC
/*
* sched_clock math assist
* ns = cycles * (ns_per_sec / cpu_freq_hz)
* ns = cycles * (10^6 / cpu_freq_khz)
* ns = cycles * (10^6 * 2^SF / cpu_freq_khz) / 2^SF
* ns = cycles * cyc2ns_scale >> SF
*/
#define CYC2NS_SF 10 /* 2^10, carefully chosen */
#define CYC2NS_SCALE ((1000000 << CYC2NS_SF) / (arc_get_core_freq() / 1000))
static unsigned long long cycles2ns(unsigned long long cyc)
{
return (cyc * CYC2NS_SCALE ) >> CYC2NS_SF;
}
/*
* Scheduler clock - a monotonically increasing clock in nanosec units.
* It's return value must NOT wrap around.
*
* - Since 32bit TIMER1 will overflow almost immediately (53sec @ 80MHz), it
* can't be used directly.
* - Using getrawmonotonic (TIMER1 based, but with state for last + current
* snapshots), is no-good either because of seqlock deadlock possibilities
* - So only with native 64bit timer we do this, otherwise fallback to generic
* jiffies based version - which despite not being fine grained gaurantees
* the monotonically increasing semantics.
*/
unsigned long long sched_clock(void)
{
return cycles2ns(arc_counter_read(NULL));
}
#endif