ARM: 7451/1: arch timer: implement read_current_timer and get_cycles
Will Deacon [Fri, 6 Jul 2012 14:46:45 +0000 (15:46 +0100)]
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>

arch/arm/include/asm/arch_timer.h
arch/arm/include/asm/timex.h
arch/arm/kernel/arch_timer.c

index ed2e95d..62e7547 100644 (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
index 3be8de3..ce11944 100644 (file)
 #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
index dd58035..dbbeec4 100644 (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,