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ARM: 7451/1: arch timer: implement read_current_timer and get_cycles

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This patch implements read_current_timer using the architected timers
when they are selected via CONFIG_ARM_ARCH_TIMER. If they are detected
not to be usable at runtime, we return -ENXIO to the caller.

Furthermore, if read_current_timer is exported then we can implement
get_cycles in terms of it for use as both an entropy source and for
implementing __udelay and friends.

Tested-by: Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
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:
Will Deacon 2012-07-06 15:46:45 +01:00 committed by Russell King
parent f8f5701bda
commit 923df96b9f
3 changed files with 17 additions and 4 deletions
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3
arch/arm/include/asm/arch_timer.h
View File

@ -1,7 +1,10 @@
#ifndef __ASMARM_ARCH_TIMER_H
#define __ASMARM_ARCH_TIMER_H
#include <asm/errno.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);
#else

10
arch/arm/include/asm/timex.h
View File

@ -12,13 +12,15 @@
#ifndef _ASMARM_TIMEX_H
#define _ASMARM_TIMEX_H
#include <asm/arch_timer.h>
#include <mach/timex.h>
typedef unsigned long cycles_t;
static inline cycles_t get_cycles (void)
{
return 0;
}
#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

8
arch/arm/kernel/arch_timer.c
View File

@ -223,6 +223,14 @@ static cycle_t arch_counter_read(struct clocksource *cs)
return arch_counter_get_cntpct();
}
int read_current_timer(unsigned long *timer_val)
{
if (!arch_timer_rate)
return -ENXIO;
*timer_val = arch_counter_get_cntpct();
return 0;
}
static struct clocksource clocksource_counter = {
.name = "arch_sys_counter",
.rating = 400,