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

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 <[email protected]> Reviewed-by: Stephen Boyd <[email protected]> Signed-off-by: Will Deacon <[email protected]> Signed-off-by: Russell King <[email protected]>
VadimAlexeev · Jul 9, 2012 · 923df96 · 923df96
1 parent f8f5701
commit 923df96
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Showing 3 changed files with 17 additions and 4 deletions.
diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
@@ -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

diff --git a/arch/arm/include/asm/timex.h b/arch/arm/include/asm/timex.h
@@ -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
diff --git a/arch/arm/kernel/arch_timer.c b/arch/arm/kernel/arch_timer.c
@@ -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,