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Commit 56942fec authored by Jonathan Austin's avatar Jonathan Austin Committed by Russell King
Browse files

ARM: 7538/1: delay: add registration mechanism for delay timer sources 



The current timer-based delay loop relies on the architected timer to
initiate the switch away from the polling-based implementation. This is
unfortunate for platforms without the architected timers but with a
suitable delay source (that is, constant frequency, always powered-up
and ticking as long as the CPUs are online).

This patch introduces a registration mechanism for the delay timer
(which provides an unconditional read_current_timer implementation) and
updates the architected timer code to use the new interface.

Reviewed-by: default avatarStephen Boyd <sboyd@codeaurora.org>
Signed-off-by: default avatarJonathan Austin <jonathan.austin@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent a1b2dde7

arch/arm/include/asm/arch_timer.h

+0 −1
Original line number Diff line number Diff line
@@ -5,7 +5,6 @@ 
#include <linux/clocksource.h>



#ifdef CONFIG_ARM_ARCH_TIMER

#define ARCH_HAS_READ_CURRENT_TIMER

int arch_timer_of_register(void);

int arch_timer_sched_clock_init(void);

struct timecounter *arch_timer_get_timecounter(void);

arch/arm/include/asm/delay.h

+9 −0
Original line number Diff line number Diff line
@@ -15,6 +15,11 @@ 


#ifndef __ASSEMBLY__



struct delay_timer {

	unsigned long (*read_current_timer)(void);

	unsigned long freq;

};



extern struct arm_delay_ops {

	void (*delay)(unsigned long);

	void (*const_udelay)(unsigned long);
@@ -56,6 +61,10 @@ extern void __loop_delay(unsigned long loops); 
extern void __loop_udelay(unsigned long usecs);

extern void __loop_const_udelay(unsigned long);



/* Delay-loop timer registration. */

#define ARCH_HAS_READ_CURRENT_TIMER

extern void register_current_timer_delay(const struct delay_timer *timer);



#endif /* __ASSEMBLY__ */



#endif /* defined(_ARM_DELAY_H) */

arch/arm/include/asm/timex.h

+0 −6
Original line number Diff line number Diff line
@@ -12,15 +12,9 @@ 
#ifndef _ASMARM_TIMEX_H

#define _ASMARM_TIMEX_H



#include <asm/arch_timer.h>

#include <mach/timex.h>



typedef unsigned long cycles_t;



#ifdef ARCH_HAS_READ_CURRENT_TIMER

#define get_cycles()	({ cycles_t c; read_current_timer(&c) ? 0 : c; })

#else

#define get_cycles()	(0)

#endif



#endif

arch/arm/kernel/arch_timer.c

+8 −9
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/io.h>



#include <asm/cputype.h>

#include <asm/delay.h>

#include <asm/localtimer.h>

#include <asm/arch_timer.h>

#include <asm/system_info.h>
@@ -39,8 +40,7 @@ enum ppi_nr { 
static int arch_timer_ppi[MAX_TIMER_PPI];



static struct clock_event_device __percpu **arch_timer_evt;



extern void init_current_timer_delay(unsigned long freq);

static struct delay_timer arch_delay_timer;



static bool arch_timer_use_virtual = true;
@@ -325,12 +325,9 @@ static cycle_t arch_counter_read(struct clocksource *cs) 
	return arch_counter_get_cntpct();

}



int read_current_timer(unsigned long *timer_val)

static unsigned long arch_timer_read_current_timer(void)

{

	if (!arch_timer_rate)

		return -ENXIO;

	*timer_val = arch_counter_get_cntpct();

	return 0;

	return arch_counter_get_cntpct();

}



static cycle_t arch_counter_read_cc(const struct cyclecounter *cc)
@@ -441,11 +438,13 @@ static int __init arch_timer_register(void) 
		arch_timer_global_evt.cpumask = cpumask_of(0);

		err = arch_timer_setup(&arch_timer_global_evt);

	}



	if (err)

		goto out_free_irq;



	init_current_timer_delay(arch_timer_rate);

	/* Use the architected timer for the delay loop. */

	arch_delay_timer.read_current_timer = &arch_timer_read_current_timer;

	arch_delay_timer.freq = arch_timer_rate;

	register_current_timer_delay(&arch_delay_timer);

	return 0;



out_free_irq:

arch/arm/lib/delay.c

+26 −8
Original line number Diff line number Diff line
@@ -34,7 +34,18 @@ struct arm_delay_ops arm_delay_ops = { 
	.udelay		= __loop_udelay,

};



#ifdef ARCH_HAS_READ_CURRENT_TIMER

static const struct delay_timer *delay_timer;

static bool delay_calibrated;



int read_current_timer(unsigned long *timer_val)

{

	if (!delay_timer)

		return -ENXIO;



	*timer_val = delay_timer->read_current_timer();

	return 0;

}



static void __timer_delay(unsigned long cycles)

{

	cycles_t start = get_cycles();
@@ -55,17 +66,24 @@ static void __timer_udelay(unsigned long usecs) 
	__timer_const_udelay(usecs * UDELAY_MULT);

}



void __init init_current_timer_delay(unsigned long freq)

void __init register_current_timer_delay(const struct delay_timer *timer)

{

	if (!delay_calibrated) {

		pr_info("Switching to timer-based delay loop\n");

	lpj_fine			= freq / HZ;

		delay_timer			= timer;

		lpj_fine			= timer->freq / HZ;

		loops_per_jiffy			= lpj_fine;

		arm_delay_ops.delay		= __timer_delay;

		arm_delay_ops.const_udelay	= __timer_const_udelay;

		arm_delay_ops.udelay		= __timer_udelay;

		delay_calibrated		= true;

	} else {

		pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");

	}

}



unsigned long __cpuinit calibrate_delay_is_known(void)

{

	delay_calibrated = true;

	return lpj_fine;

}
 
#endif