[PATCH -v5 02/11] MIPS: add mips_timecounter_read() to get high precision timestamp

Wu Zhangjin
2009-10-25T15:17:29Z

This patch implement a mips_timecounter_read(), which can be used 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