From 389fb7bf0cf78caf9811affde36eac6d80dd9bda Mon Sep 17 00:00:00 2001
From: =?utf8?q?=E9=BB=84=E6=B6=9B?= <huangtao@rock-chips.com>
Date: Fri, 28 Mar 2014 17:56:56 +0800
Subject: [PATCH] Revert "clocksource: arch_timer: use virtual counters"

This reverts commit 714c21cb90951905b269870087a99c37f3a7af0c.
---
 arch/arm/include/asm/arch_timer.h    |  9 +++++++++
 arch/arm64/include/asm/arch_timer.h  | 10 ++++++++++
 drivers/clocksource/arm_arch_timer.c | 23 ++++++++++++++++++-----
 include/clocksource/arm_arch_timer.h |  2 +-
 4 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
index f693038b8881..4928cdacedf0 100644
--- a/arch/arm/include/asm/arch_timer.h
+++ b/arch/arm/include/asm/arch_timer.h
@@ -80,6 +80,15 @@ static inline u32 arch_timer_get_cntfrq(void)
 	return val;
 }
 
+static inline u64 arch_counter_get_cntpct(void)
+{
+	u64 cval;
+
+	isb();
+	asm volatile("mrrc p15, 0, %Q0, %R0, c14" : "=r" (cval));
+	return cval;
+}
+
 static inline u64 arch_counter_get_cntvct(void)
 {
 	u64 cval;
diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
index d56ed11ba9a3..bf6ab242f047 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -110,6 +110,16 @@ static inline void __cpuinit arch_counter_set_user_access(void)
 	asm volatile("msr	cntkctl_el1, %0" : : "r" (cntkctl));
 }
 
+static inline u64 arch_counter_get_cntpct(void)
+{
+	u64 cval;
+
+	isb();
+	asm volatile("mrs %0, cntpct_el0" : "=r" (cval));
+
+	return cval;
+}
+
 static inline u64 arch_counter_get_cntvct(void)
 {
 	u64 cval;
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 053d846ab5b1..a2b254189782 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -186,19 +186,27 @@ u32 arch_timer_get_rate(void)
 	return arch_timer_rate;
 }
 
-u64 arch_timer_read_counter(void)
+/*
+ * Some external users of arch_timer_read_counter (e.g. sched_clock) may try to
+ * call it before it has been initialised. Rather than incur a performance
+ * penalty checking for initialisation, provide a default implementation that
+ * won't lead to time appearing to jump backwards.
+ */
+static u64 arch_timer_read_zero(void)
 {
-	return arch_counter_get_cntvct();
+	return 0;
 }
 
+u64 (*arch_timer_read_counter)(void) = arch_timer_read_zero;
+
 static cycle_t arch_counter_read(struct clocksource *cs)
 {
-	return arch_counter_get_cntvct();
+	return arch_timer_read_counter();
 }
 
 static cycle_t arch_counter_read_cc(const struct cyclecounter *cc)
 {
-	return arch_counter_get_cntvct();
+	return arch_timer_read_counter();
 }
 
 static struct clocksource clocksource_counter = {
@@ -279,7 +287,7 @@ static int __init arch_timer_register(void)
 	cyclecounter.mult = clocksource_counter.mult;
 	cyclecounter.shift = clocksource_counter.shift;
 	timecounter_init(&timecounter, &cyclecounter,
-			 arch_counter_get_cntvct());
+			 arch_counter_get_cntpct());
 
 	if (arch_timer_use_virtual) {
 		ppi = arch_timer_ppi[VIRT_PPI];
@@ -368,6 +376,11 @@ static void __init arch_timer_init(struct device_node *np)
 		}
 	}
 
+	if (arch_timer_use_virtual)
+		arch_timer_read_counter = arch_counter_get_cntvct;
+	else
+		arch_timer_read_counter = arch_counter_get_cntpct;
+
 	arch_timer_register();
 	arch_timer_arch_init();
 }
diff --git a/include/clocksource/arm_arch_timer.h b/include/clocksource/arm_arch_timer.h
index c463ce990c48..e6c9c4cc9b23 100644
--- a/include/clocksource/arm_arch_timer.h
+++ b/include/clocksource/arm_arch_timer.h
@@ -32,7 +32,7 @@
 #ifdef CONFIG_ARM_ARCH_TIMER
 
 extern u32 arch_timer_get_rate(void);
-extern u64 arch_timer_read_counter(void);
+extern u64 (*arch_timer_read_counter)(void);
 extern struct timecounter *arch_timer_get_timecounter(void);
 
 #else
-- 
2.34.1