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

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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: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Jonathan Austin <jonathan.austin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Jonathan Austin 2012-09-21 18:51:44 +01:00 committed by Russell King
parent a1b2dde704
commit 56942fec06
5 changed files with 43 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/arm/include/asm/arch_timer.h
View File

@ -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);

9
arch/arm/include/asm/delay.h
View File

@ -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) */

6
arch/arm/include/asm/timex.h
View File

@ -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

17
arch/arm/kernel/arch_timer.c
View File

@ -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:

34
arch/arm/lib/delay.c
View File

@ -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)
{
pr_info("Switching to timer-based delay loop\n");
lpj_fine = freq / HZ;
arm_delay_ops.delay = __timer_delay;
arm_delay_ops.const_udelay = __timer_const_udelay;
arm_delay_ops.udelay = __timer_udelay;
if (!delay_calibrated) {
pr_info("Switching to timer-based delay loop\n");
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