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: 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>
diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
index ad9b155..d40229d 100644
--- a/arch/arm/include/asm/arch_timer.h
+++ b/arch/arm/include/asm/arch_timer.h
@@ -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);
diff --git a/arch/arm/include/asm/delay.h b/arch/arm/include/asm/delay.h
index dc61451..ab98fdd 100644
--- a/arch/arm/include/asm/delay.h
+++ b/arch/arm/include/asm/delay.h
@@ -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_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) */
diff --git a/arch/arm/include/asm/timex.h b/arch/arm/include/asm/timex.h
index ce11944..9acc135 100644
--- a/arch/arm/include/asm/timex.h
+++ b/arch/arm/include/asm/timex.h
@@ -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
diff --git a/arch/arm/kernel/arch_timer.c b/arch/arm/kernel/arch_timer.c
index c04c2a6..c8ef207 100644
--- a/arch/arm/kernel/arch_timer.c
+++ b/arch/arm/kernel/arch_timer.c
@@ -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 @@
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 @@
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 @@
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:
diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c
index d6dacc6..9d0a300 100644
--- a/arch/arm/lib/delay.c
+++ b/arch/arm/lib/delay.c
@@ -34,7 +34,18 @@
.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 @@
__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