Hi,
I'm wondering the code for checking whether a high-precision code is
available should be in mach_clock.c or in the machine-dependent
directory. In this patch it's in the machine-dependent directory. It can
ensure the backward compactability. Otherwise compiling a gnumach with
only '../configure' will cause page fault at the startup.
```
+uint32_t
+hpclock_read_counter(void)
+{
+ if (hpet_addr != NULL)
+ return HPET32(HPET_COUNTER);
+ else
+ return 0;
+}
+
+uint32_t
+hpclock_get_counter_period_nsec(void)
+{
+ if (hpet_addr != NULL)
+ return hpet_period_nsec;
+ else
+ return 0;
+}
```
Zhaoming
---
i386/i386/apic.c | 17 +++++++++++++++++
i386/i386at/model_dep.c | 2 ++
kern/mach_clock.c | 36 +++++++++++++++++++++++++++++++++++-
kern/mach_clock.h | 4 ++++
4 files changed, 58 insertions(+), 1 deletion(-)
diff --git a/i386/i386/apic.c b/i386/i386/apic.c
index 77d555b5..6cacd5fa 100644
--- a/i386/i386/apic.c
+++ b/i386/i386/apic.c
@@ -479,3 +479,20 @@ hpet_mdelay(uint32_t ms)
hpet_udelay(ms * 1000);
}
+uint32_t
+hpclock_read_counter(void)
+{
+ if (hpet_addr != NULL)
+ return HPET32(HPET_COUNTER);
+ else
+ return 0;
+}
+
+uint32_t
+hpclock_get_counter_period_nsec(void)
+{
+ if (hpet_addr != NULL)
+ return hpet_period_nsec;
+ else
+ return 0;
+}
diff --git a/i386/i386at/model_dep.c b/i386/i386at/model_dep.c
index 30449c37..42dadeb8 100644
--- a/i386/i386at/model_dep.c
+++ b/i386/i386at/model_dep.c
@@ -223,7 +223,9 @@ void machine_init(void)
*/
gdt_descr_tmp.linear_base += apboot_addr;
apboot_jmp_offset += apboot_addr;
+#endif
+#ifdef APIC
/*
* Initialize the HPET
*/
diff --git a/kern/mach_clock.c b/kern/mach_clock.c
index 5501b7b8..9bae3439 100644
--- a/kern/mach_clock.c
+++ b/kern/mach_clock.c
@@ -83,6 +83,15 @@ unsigned tickadj = 500 / HZ; /* can adjust 100 usecs
per second */
unsigned bigadj = 1000000; /* adjust 10*tickadj if adjustment
> bigadj */
+/* A high-precision (hardware) clock is taken into account to increase the
+ * accuracy of the functions used for getting time (e.g. host_get_time64()).
+ * The counter of the clock is read once in every clock interrupt. When any
+ * of the functions used for getting time is called, the counter is read again
+ * and the difference between these two read is multiplied by the counter
+ * period and added to the read value from time or uptime to get a more
+ * accurate time read. */
+uint32_t last_hpc_read = 0;
+
/*
* This update protocol, with a check value, allows
* do {
@@ -128,7 +137,8 @@ MACRO_BEGIN
\
__sync_synchronize(); \
(time)->nanoseconds = mtime->time_value.nanoseconds; \
__sync_synchronize(); \
- } while ((time)->seconds != mtime->check_seconds64); \
+ } while ((time)->seconds != mtime->check_seconds64); \
+ time_value64_add_hpc(time); \
MACRO_END
#define read_mapped_uptime(uptime) \
@@ -139,6 +149,7 @@ MACRO_BEGIN
\
(uptime)->nanoseconds = mtime->uptime_value.nanoseconds;\
__sync_synchronize(); \
} while ((uptime)->seconds != mtime->check_upseconds64); \
+ time_value64_add_hpc(uptime); \
MACRO_END
def_simple_lock_irq_data(static, timer_lock) /* lock for ... */
@@ -292,6 +303,7 @@ void clock_interrupt(
}
}
}
+ last_hpc_read = hpclock_read_counter();
}
/*
@@ -426,6 +438,28 @@ clock_boottime_update(const struct time_value64 *new_time)
time_value64_add(&clock_boottime_offset, &delta);
}
+/*
+ * Add the time value since last clock interrupt in nanosecond.
+ */
+static void
+time_value64_add_hpc(time_value64_t *value)
+{
+ uint32_t now = hpclock_read_counter();
+ /* Time since last clock interrupt in nanosecond. */
+ int64_t ns = (now - last_hpc_read) * hpclock_get_counter_period_nsec();
+
+ /* Limit the value of ns under the period of a clock interrupt in case
+ imprecise computation causes ns greater than the clock interrupt
+ period. */
+ if (ns > tick * 1000)
+ /* Let ns stuck at the end of the clock interrupt period when
+ something bad happens. */
+ ns = (tick * 1000) - 1;
+
+ time_value64_add_nanos(value, ns);
+}
+
+
/*
* Record a timestamp in STAMP. Records values in the boot-time clock
* frame.
diff --git a/kern/mach_clock.h b/kern/mach_clock.h
index d4f04f5e..e83b638c 100644
--- a/kern/mach_clock.h
+++ b/kern/mach_clock.h
@@ -110,4 +110,8 @@ extern boolean_t untimeout(timer_func_t *fcn, const void
*param);
extern int timeopen(dev_t dev, int flag, io_req_t ior);
extern void timeclose(dev_t dev, int flag);
+/* For high-precision clocks. */
+extern uint32_t hpclock_read_counter(void);
+extern uint32_t hpclock_get_counter_period_nsec(void);
+
#endif /* _KERN_MACH_CLOCK_H_ */
--
2.47.2
