[PATCH -v6 02/13] tracing: add mips_timecounter_read() for MIPS

[Wu Zhangjin <wuzhangjin@gmail.com>]

This patch add a new function: mips_timecounter_read() to get high
precision timestamp without extra lock.

It is based on the clock counter register and the
timecounter/cyclecounter abstraction layer of kernel.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
---
 arch/mips/include/asm/time.h |   19 +++++++++++++++++++
 arch/mips/kernel/csrc-r4k.c  |   41 +++++++++++++++++++++++++++++++++++++++++
 arch/mips/kernel/time.c      |    2 ++
 3 files changed, 62 insertions(+), 0 deletions(-)

diff --git a/arch/mips/include/asm/time.h b/arch/mips/include/asm/time.h
index df6a430..b8af7fa 100644
--- a/arch/mips/include/asm/time.h
+++ b/arch/mips/include/asm/time.h
@@ -73,8 +73,18 @@ static inline int mips_clockevent_init(void)
  */
 #ifdef CONFIG_CSRC_R4K_LIB
 extern int init_r4k_clocksource(void);
+extern int init_r4k_timecounter(void);
+extern u64 r4k_timecounter_read(void);
 #endif
 
+static inline u64 mips_timecounter_read(void)
+{
+#ifdef CONFIG_CSRC_R4K
+	return r4k_timecounter_read();
+#else
+	return sched_clock();
+#endif
+}
 static inline int init_mips_clocksource(void)
 {
 #ifdef CONFIG_CSRC_R4K
@@ -84,6 +94,15 @@ static inline int init_mips_clocksource(void)
 #endif
 }
 
+static inline int init_mips_timecounter(void)
+{
+#ifdef CONFIG_CSRC_R4K
+	return init_r4k_timecounter();
+#else
+	return 0;
+#endif
+}
+
 extern void clocksource_set_clock(struct clocksource *cs, unsigned int clock);
 extern void clockevent_set_clock(struct clock_event_device *cd,
 		unsigned int clock);
diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c
index e95a3cd..4e7705f 100644
--- a/arch/mips/kernel/csrc-r4k.c
+++ b/arch/mips/kernel/csrc-r4k.c
@@ -7,6 +7,7 @@
  */
 #include <linux/clocksource.h>
 #include <linux/init.h>
+#include <linux/sched.h>
 
 #include <asm/time.h>
 
@@ -36,3 +37,43 @@ int __init init_r4k_clocksource(void)
 
 	return 0;
 }
+
+static struct timecounter r4k_tc = {
+	.cc = NULL,
+};
+
+static cycle_t r4k_cc_read(const struct cyclecounter *cc)
+{
+	return read_c0_count();
+}
+
+static struct cyclecounter r4k_cc = {
+	.read = r4k_cc_read,
+	.mask = CLOCKSOURCE_MASK(32),
+	.shift = 32,
+};
+
+int __init init_r4k_timecounter(void)
+{
+	if (!cpu_has_counter || !mips_hpt_frequency)
+		return -ENXIO;
+
+	r4k_cc.mult = div_sc((unsigned long)mips_hpt_frequency, NSEC_PER_SEC,
+			32);
+
+	timecounter_init(&r4k_tc, &r4k_cc, sched_clock());
+
+	return 0;
+}
+
+u64 r4k_timecounter_read(void)
+{
+	u64 clock;
+
+	if (r4k_tc.cc != NULL)
+		clock = timecounter_read(&r4k_tc);
+	else
+		clock = sched_clock();
+
+	return clock;
+}
diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c
index 1f467d5..e38cca1 100644
--- a/arch/mips/kernel/time.c
+++ b/arch/mips/kernel/time.c
@@ -156,4 +156,6 @@ void __init time_init(void)
 
 	if (!mips_clockevent_init() || !cpu_has_mfc0_count_bug())
 		init_mips_clocksource();
+	if (!cpu_has_mfc0_count_bug())
+		init_mips_timecounter();
 }
-- 
1.6.2.1