* [PATCH 1/8] time: Add cycles to nanoseconds translation
2016-03-03 4:21 [PATCH 0/8][GIT PULL] time: Cross-timestamp infrastructure for 4.6 John Stultz
@ 2016-03-03 4:21 ` John Stultz
2016-03-03 4:21 ` [PATCH 2/8] time: Add timekeeping snapshot code capturing system time and counter John Stultz
` (6 subsequent siblings)
7 siblings, 0 replies; 14+ messages in thread
From: John Stultz @ 2016-03-03 4:21 UTC (permalink / raw)
To: lkml
Cc: Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, kevin.b.stanton,
kevin.j.clarke, hpa, jeffrey.t.kirsher, netdev, John Stultz
From: "Christopher S. Hall" <christopher.s.hall@intel.com>
The timekeeping code does not currently provide a way to translate
externally provided clocksource cycles to system time. The cycle count
is always provided by the result clocksource read() method internal to
the timekeeping code. The added function timekeeping_cycles_to_ns()
calculated a nanosecond value from a cycle count that can be added to
tk_read_base.base value yielding the current system time. This allows
clocksource cycle values external to the timekeeping code to provide a
cycle count that can be transformed to system time.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
kernel/time/timekeeping.c | 25 +++++++++++++++++++++----
1 file changed, 21 insertions(+), 4 deletions(-)
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 34b4ced..4243d28 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -298,17 +298,34 @@ u32 (*arch_gettimeoffset)(void) = default_arch_gettimeoffset;
static inline u32 arch_gettimeoffset(void) { return 0; }
#endif
+static inline s64 timekeeping_delta_to_ns(struct tk_read_base *tkr,
+ cycle_t delta)
+{
+ s64 nsec;
+
+ nsec = delta * tkr->mult + tkr->xtime_nsec;
+ nsec >>= tkr->shift;
+
+ /* If arch requires, add in get_arch_timeoffset() */
+ return nsec + arch_gettimeoffset();
+}
+
static inline s64 timekeeping_get_ns(struct tk_read_base *tkr)
{
cycle_t delta;
- s64 nsec;
delta = timekeeping_get_delta(tkr);
+ return timekeeping_delta_to_ns(tkr, delta);
+}
- nsec = (delta * tkr->mult + tkr->xtime_nsec) >> tkr->shift;
+static inline s64 timekeeping_cycles_to_ns(struct tk_read_base *tkr,
+ cycle_t cycles)
+{
+ cycle_t delta;
- /* If arch requires, add in get_arch_timeoffset() */
- return nsec + arch_gettimeoffset();
+ /* calculate the delta since the last update_wall_time */
+ delta = clocksource_delta(cycles, tkr->cycle_last, tkr->mask);
+ return timekeeping_delta_to_ns(tkr, delta);
}
/**
--
1.9.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH 2/8] time: Add timekeeping snapshot code capturing system time and counter
2016-03-03 4:21 [PATCH 0/8][GIT PULL] time: Cross-timestamp infrastructure for 4.6 John Stultz
2016-03-03 4:21 ` [PATCH 1/8] time: Add cycles to nanoseconds translation John Stultz
@ 2016-03-03 4:21 ` John Stultz
2016-03-03 4:21 ` [PATCH 3/8] time: Remove duplicated code in ktime_get_raw_and_real() John Stultz
` (5 subsequent siblings)
7 siblings, 0 replies; 14+ messages in thread
From: John Stultz @ 2016-03-03 4:21 UTC (permalink / raw)
To: lkml
Cc: Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, kevin.b.stanton,
kevin.j.clarke, hpa, jeffrey.t.kirsher, netdev, John Stultz
From: "Christopher S. Hall" <christopher.s.hall@intel.com>
In the current timekeeping code there isn't any interface to
atomically capture the current relationship between the system counter
and system time. ktime_get_snapshot() returns this triple (counter,
monotonic raw, realtime) in the system_time_snapshot struct.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
[jstultz: Moved structure definitions around to clean things up,
fixed cycles_t/cycle_t confusion.]
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
include/linux/timekeeping.h | 18 ++++++++++++++++++
kernel/time/timekeeping.c | 30 ++++++++++++++++++++++++++++++
2 files changed, 48 insertions(+)
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index ec89d84..7817591 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -267,6 +267,24 @@ extern void ktime_get_raw_and_real_ts64(struct timespec64 *ts_raw,
struct timespec64 *ts_real);
/*
+ * struct system_time_snapshot - simultaneous raw/real time capture with
+ * counter value
+ * @cycles: Clocksource counter value to produce the system times
+ * @real: Realtime system time
+ * @raw: Monotonic raw system time
+ */
+struct system_time_snapshot {
+ cycle_t cycles;
+ ktime_t real;
+ ktime_t raw;
+};
+
+/*
+ * Simultaneously snapshot realtime and monotonic raw clocks
+ */
+extern void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot);
+
+/*
* Persistent clock related interfaces
*/
extern int persistent_clock_is_local;
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 4243d28..89b4695 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -874,6 +874,36 @@ time64_t __ktime_get_real_seconds(void)
return tk->xtime_sec;
}
+/**
+ * ktime_get_snapshot - snapshots the realtime/monotonic raw clocks with counter
+ * @systime_snapshot: pointer to struct receiving the system time snapshot
+ */
+void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
+{
+ struct timekeeper *tk = &tk_core.timekeeper;
+ unsigned long seq;
+ ktime_t base_raw;
+ ktime_t base_real;
+ s64 nsec_raw;
+ s64 nsec_real;
+ cycle_t now;
+
+ do {
+ seq = read_seqcount_begin(&tk_core.seq);
+
+ now = tk->tkr_mono.read(tk->tkr_mono.clock);
+ base_real = ktime_add(tk->tkr_mono.base,
+ tk_core.timekeeper.offs_real);
+ base_raw = tk->tkr_raw.base;
+ nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, now);
+ nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw, now);
+ } while (read_seqcount_retry(&tk_core.seq, seq));
+
+ systime_snapshot->cycles = now;
+ systime_snapshot->real = ktime_add_ns(base_real, nsec_real);
+ systime_snapshot->raw = ktime_add_ns(base_raw, nsec_raw);
+}
+EXPORT_SYMBOL_GPL(ktime_get_snapshot);
#ifdef CONFIG_NTP_PPS
--
1.9.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH 3/8] time: Remove duplicated code in ktime_get_raw_and_real()
2016-03-03 4:21 [PATCH 0/8][GIT PULL] time: Cross-timestamp infrastructure for 4.6 John Stultz
2016-03-03 4:21 ` [PATCH 1/8] time: Add cycles to nanoseconds translation John Stultz
2016-03-03 4:21 ` [PATCH 2/8] time: Add timekeeping snapshot code capturing system time and counter John Stultz
@ 2016-03-03 4:21 ` John Stultz
2016-03-03 4:21 ` [PATCH 4/8] time: Add driver cross timestamp interface for higher precision time synchronization John Stultz
` (4 subsequent siblings)
7 siblings, 0 replies; 14+ messages in thread
From: John Stultz @ 2016-03-03 4:21 UTC (permalink / raw)
To: lkml
Cc: Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, kevin.b.stanton,
kevin.j.clarke, hpa, jeffrey.t.kirsher, netdev, John Stultz
From: "Christopher S. Hall" <christopher.s.hall@intel.com>
The code in ktime_get_snapshot() is a superset of the code in
ktime_get_raw_and_real() code. Further, ktime_get_raw_and_real() is
called only by the PPS code, pps_get_ts(). Consolidate the
pps_get_ts() code into a single function calling ktime_get_snapshot()
and eliminate ktime_get_raw_and_real(). A side effect of this is that
the raw and real results of pps_get_ts() correspond to exactly the
same clock cycle. Previously these values represented separate reads
of the system clock.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
include/linux/pps_kernel.h | 17 ++++++-----------
kernel/time/timekeeping.c | 40 ++--------------------------------------
2 files changed, 8 insertions(+), 49 deletions(-)
diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
index 54bf148..35ac903 100644
--- a/include/linux/pps_kernel.h
+++ b/include/linux/pps_kernel.h
@@ -111,22 +111,17 @@ static inline void timespec_to_pps_ktime(struct pps_ktime *kt,
kt->nsec = ts.tv_nsec;
}
-#ifdef CONFIG_NTP_PPS
-
static inline void pps_get_ts(struct pps_event_time *ts)
{
- ktime_get_raw_and_real_ts64(&ts->ts_raw, &ts->ts_real);
-}
+ struct system_time_snapshot snap;
-#else /* CONFIG_NTP_PPS */
-
-static inline void pps_get_ts(struct pps_event_time *ts)
-{
- ktime_get_real_ts64(&ts->ts_real);
+ ktime_get_snapshot(&snap);
+ ts->ts_real = ktime_to_timespec64(snap.real);
+#ifdef CONFIG_NTP_PPS
+ ts->ts_raw = ktime_to_timespec64(snap.raw);
+#endif
}
-#endif /* CONFIG_NTP_PPS */
-
/* Subtract known time delay from PPS event time(s) */
static inline void pps_sub_ts(struct pps_event_time *ts, struct timespec64 delta)
{
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 89b4695..af19a49 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -888,6 +888,8 @@ void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
s64 nsec_real;
cycle_t now;
+ WARN_ON_ONCE(timekeeping_suspended);
+
do {
seq = read_seqcount_begin(&tk_core.seq);
@@ -905,44 +907,6 @@ void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
}
EXPORT_SYMBOL_GPL(ktime_get_snapshot);
-#ifdef CONFIG_NTP_PPS
-
-/**
- * ktime_get_raw_and_real_ts64 - get day and raw monotonic time in timespec format
- * @ts_raw: pointer to the timespec to be set to raw monotonic time
- * @ts_real: pointer to the timespec to be set to the time of day
- *
- * This function reads both the time of day and raw monotonic time at the
- * same time atomically and stores the resulting timestamps in timespec
- * format.
- */
-void ktime_get_raw_and_real_ts64(struct timespec64 *ts_raw, struct timespec64 *ts_real)
-{
- struct timekeeper *tk = &tk_core.timekeeper;
- unsigned long seq;
- s64 nsecs_raw, nsecs_real;
-
- WARN_ON_ONCE(timekeeping_suspended);
-
- do {
- seq = read_seqcount_begin(&tk_core.seq);
-
- *ts_raw = tk->raw_time;
- ts_real->tv_sec = tk->xtime_sec;
- ts_real->tv_nsec = 0;
-
- nsecs_raw = timekeeping_get_ns(&tk->tkr_raw);
- nsecs_real = timekeeping_get_ns(&tk->tkr_mono);
-
- } while (read_seqcount_retry(&tk_core.seq, seq));
-
- timespec64_add_ns(ts_raw, nsecs_raw);
- timespec64_add_ns(ts_real, nsecs_real);
-}
-EXPORT_SYMBOL(ktime_get_raw_and_real_ts64);
-
-#endif /* CONFIG_NTP_PPS */
-
/**
* do_gettimeofday - Returns the time of day in a timeval
* @tv: pointer to the timeval to be set
--
1.9.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH 4/8] time: Add driver cross timestamp interface for higher precision time synchronization
2016-03-03 4:21 [PATCH 0/8][GIT PULL] time: Cross-timestamp infrastructure for 4.6 John Stultz
` (2 preceding siblings ...)
2016-03-03 4:21 ` [PATCH 3/8] time: Remove duplicated code in ktime_get_raw_and_real() John Stultz
@ 2016-03-03 4:21 ` John Stultz
2016-03-03 4:21 ` [PATCH 5/8] time: Add history to cross timestamp interface supporting slower devices John Stultz
` (3 subsequent siblings)
7 siblings, 0 replies; 14+ messages in thread
From: John Stultz @ 2016-03-03 4:21 UTC (permalink / raw)
To: lkml
Cc: Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, kevin.b.stanton,
kevin.j.clarke, hpa, jeffrey.t.kirsher, netdev, John Stultz
From: "Christopher S. Hall" <christopher.s.hall@intel.com>
ACKNOWLEDGMENT: cross timestamp code was developed by Thomas Gleixner
<tglx@linutronix.de>. It has changed considerably and any mistakes are
mine.
The precision with which events on multiple networked systems can be
synchronized using, as an example, PTP (IEEE 1588, 802.1AS) is limited
by the precision of the cross timestamps between the system clock and
the device (timestamp) clock. Precision here is the degree of
simultaneity when capturing the cross timestamp.
Currently the PTP cross timestamp is captured in software using the
PTP device driver ioctl PTP_SYS_OFFSET. Reads of the device clock are
interleaved with reads of the realtime clock. At best, the precision
of this cross timestamp is on the order of several microseconds due to
software latencies. Sub-microsecond precision is required for
industrial control and some media applications. To achieve this level
of precision hardware supported cross timestamping is needed.
The function get_device_system_crosstimestamp() allows device drivers
to return a cross timestamp with system time properly scaled to
nanoseconds. The realtime value is needed to discipline that clock
using PTP and the monotonic raw value is used for applications that
don't require a "real" time, but need an unadjusted clock time. The
get_device_system_crosstimestamp() code calls back into the driver to
ensure that the system counter is within the current timekeeping
update interval.
Modern Intel hardware provides an Always Running Timer (ART) which is
exactly related to TSC through a known frequency ratio. The ART is
routed to devices on the system and is used to precisely and
simultaneously capture the device clock with the ART.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
[jstultz: Reworked to remove extra structures and simplify calling]
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
include/linux/timekeeping.h | 35 ++++++++++++++++++++++++++++
kernel/time/timekeeping.c | 56 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 91 insertions(+)
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 7817591..4a2ca65 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -280,6 +280,41 @@ struct system_time_snapshot {
};
/*
+ * struct system_device_crosststamp - system/device cross-timestamp
+ * (syncronized capture)
+ * @device: Device time
+ * @sys_realtime: Realtime simultaneous with device time
+ * @sys_monoraw: Monotonic raw simultaneous with device time
+ */
+struct system_device_crosststamp {
+ ktime_t device;
+ ktime_t sys_realtime;
+ ktime_t sys_monoraw;
+};
+
+/*
+ * struct system_counterval_t - system counter value with the pointer to the
+ * corresponding clocksource
+ * @cycles: System counter value
+ * @cs: Clocksource corresponding to system counter value. Used by
+ * timekeeping code to verify comparibility of two cycle values
+ */
+struct system_counterval_t {
+ cycle_t cycles;
+ struct clocksource *cs;
+};
+
+/*
+ * Get cross timestamp between system clock and device clock
+ */
+extern int get_device_system_crosststamp(
+ int (*get_time_fn)(ktime_t *device_time,
+ struct system_counterval_t *system_counterval,
+ void *ctx),
+ void *ctx,
+ struct system_device_crosststamp *xtstamp);
+
+/*
* Simultaneously snapshot realtime and monotonic raw clocks
*/
extern void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index af19a49..dba595c 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -908,6 +908,62 @@ void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
EXPORT_SYMBOL_GPL(ktime_get_snapshot);
/**
+ * get_device_system_crosststamp - Synchronously capture system/device timestamp
+ * @sync_devicetime: Callback to get simultaneous device time and
+ * system counter from the device driver
+ * @xtstamp: Receives simultaneously captured system and device time
+ *
+ * Reads a timestamp from a device and correlates it to system time
+ */
+int get_device_system_crosststamp(int (*get_time_fn)
+ (ktime_t *device_time,
+ struct system_counterval_t *sys_counterval,
+ void *ctx),
+ void *ctx,
+ struct system_device_crosststamp *xtstamp)
+{
+ struct system_counterval_t system_counterval;
+ struct timekeeper *tk = &tk_core.timekeeper;
+ ktime_t base_real, base_raw;
+ s64 nsec_real, nsec_raw;
+ unsigned long seq;
+ int ret;
+
+ do {
+ seq = read_seqcount_begin(&tk_core.seq);
+ /*
+ * Try to synchronously capture device time and a system
+ * counter value calling back into the device driver
+ */
+ ret = get_time_fn(&xtstamp->device, &system_counterval, ctx);
+ if (ret)
+ return ret;
+
+ /*
+ * Verify that the clocksource associated with the captured
+ * system counter value is the same as the currently installed
+ * timekeeper clocksource
+ */
+ if (tk->tkr_mono.clock != system_counterval.cs)
+ return -ENODEV;
+
+ base_real = ktime_add(tk->tkr_mono.base,
+ tk_core.timekeeper.offs_real);
+ base_raw = tk->tkr_raw.base;
+
+ nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono,
+ system_counterval.cycles);
+ nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw,
+ system_counterval.cycles);
+ } while (read_seqcount_retry(&tk_core.seq, seq));
+
+ xtstamp->sys_realtime = ktime_add_ns(base_real, nsec_real);
+ xtstamp->sys_monoraw = ktime_add_ns(base_raw, nsec_raw);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(get_device_system_crosststamp);
+
+/**
* do_gettimeofday - Returns the time of day in a timeval
* @tv: pointer to the timeval to be set
*
--
1.9.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH 5/8] time: Add history to cross timestamp interface supporting slower devices
2016-03-03 4:21 [PATCH 0/8][GIT PULL] time: Cross-timestamp infrastructure for 4.6 John Stultz
` (3 preceding siblings ...)
2016-03-03 4:21 ` [PATCH 4/8] time: Add driver cross timestamp interface for higher precision time synchronization John Stultz
@ 2016-03-03 4:21 ` John Stultz
2016-03-03 4:21 ` [PATCH 6/8] x86: tsc: Always Running Timer (ART) correlated clocksource John Stultz
` (2 subsequent siblings)
7 siblings, 0 replies; 14+ messages in thread
From: John Stultz @ 2016-03-03 4:21 UTC (permalink / raw)
To: lkml
Cc: Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, kevin.b.stanton,
kevin.j.clarke, hpa, jeffrey.t.kirsher, netdev, John Stultz
From: "Christopher S. Hall" <christopher.s.hall@intel.com>
Another representative use case of time sync and the correlated
clocksource (in addition to PTP noted above) is PTP synchronized
audio.
In a streaming application, as an example, samples will be sent and/or
received by multiple devices with a presentation time that is in terms
of the PTP master clock. Synchronizing the audio output on these
devices requires correlating the audio clock with the PTP master
clock. The more precise this correlation is, the better the audio
quality (i.e. out of sync audio sounds bad).
>From an application standpoint, to correlate the PTP master clock with
the audio device clock, the system clock is used as a intermediate
timebase. The transforms such an application would perform are:
System Clock <-> Audio clock
System Clock <-> Network Device Clock [<-> PTP Master Clock]
Modern Intel platforms can perform a more accurate cross timestamp in
hardware (ART,audio device clock). The audio driver requires
ART->system time transforms -- the same as required for the network
driver. These platforms offload audio processing (including
cross-timestamps) to a DSP which to ensure uninterrupted audio
processing, communicates and response to the host only once every
millsecond. As a result is takes up to a millisecond for the DSP to
receive a request, the request is processed by the DSP, the audio
output hardware is polled for completion, the result is copied into
shared memory, and the host is notified. All of these operation occur
on a millisecond cadence. This transaction requires about 2 ms, but
under heavier workloads it may take up to 4 ms.
Adding a history allows these slow devices the option of providing an
ART value outside of the current interval. In this case, the callback
provided is an accessor function for the previously obtained counter
value. If get_system_device_crosststamp() receives a counter value
previous to cycle_last, it consults the history provided as an
argument in history_ref and interpolates the realtime and monotonic
raw system time using the provided counter value. If there are any
clock discontinuities, e.g. from calling settimeofday(), the monotonic
raw time is interpolated in the usual way, but the realtime clock time
is adjusted by scaling the monotonic raw adjustment.
When an accessor function is used a history argument *must* be
provided. The history is initialized using ktime_get_snapshot() and
must be called before the counter values are read.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
[jstultz: Fixed up cycles_t/cycle_t type confusion]
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
include/linux/timekeeper_internal.h | 2 +
include/linux/timekeeping.h | 5 ++
kernel/time/timekeeping.c | 171 +++++++++++++++++++++++++++++++++++-
3 files changed, 177 insertions(+), 1 deletion(-)
diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h
index 2524722..e880054 100644
--- a/include/linux/timekeeper_internal.h
+++ b/include/linux/timekeeper_internal.h
@@ -50,6 +50,7 @@ struct tk_read_base {
* @offs_tai: Offset clock monotonic -> clock tai
* @tai_offset: The current UTC to TAI offset in seconds
* @clock_was_set_seq: The sequence number of clock was set events
+ * @cs_was_changed_seq: The sequence number of clocksource change events
* @next_leap_ktime: CLOCK_MONOTONIC time value of a pending leap-second
* @raw_time: Monotonic raw base time in timespec64 format
* @cycle_interval: Number of clock cycles in one NTP interval
@@ -91,6 +92,7 @@ struct timekeeper {
ktime_t offs_tai;
s32 tai_offset;
unsigned int clock_was_set_seq;
+ u8 cs_was_changed_seq;
ktime_t next_leap_ktime;
struct timespec64 raw_time;
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 4a2ca65..96f37be 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -272,11 +272,15 @@ extern void ktime_get_raw_and_real_ts64(struct timespec64 *ts_raw,
* @cycles: Clocksource counter value to produce the system times
* @real: Realtime system time
* @raw: Monotonic raw system time
+ * @clock_was_set_seq: The sequence number of clock was set events
+ * @cs_was_changed_seq: The sequence number of clocksource change events
*/
struct system_time_snapshot {
cycle_t cycles;
ktime_t real;
ktime_t raw;
+ unsigned int clock_was_set_seq;
+ u8 cs_was_changed_seq;
};
/*
@@ -312,6 +316,7 @@ extern int get_device_system_crosststamp(
struct system_counterval_t *system_counterval,
void *ctx),
void *ctx,
+ struct system_time_snapshot *history,
struct system_device_crosststamp *xtstamp);
/*
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index dba595c..931b0b1 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -233,6 +233,7 @@ static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
u64 tmp, ntpinterval;
struct clocksource *old_clock;
+ ++tk->cs_was_changed_seq;
old_clock = tk->tkr_mono.clock;
tk->tkr_mono.clock = clock;
tk->tkr_mono.read = clock->read;
@@ -894,6 +895,8 @@ void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
seq = read_seqcount_begin(&tk_core.seq);
now = tk->tkr_mono.read(tk->tkr_mono.clock);
+ systime_snapshot->cs_was_changed_seq = tk->cs_was_changed_seq;
+ systime_snapshot->clock_was_set_seq = tk->clock_was_set_seq;
base_real = ktime_add(tk->tkr_mono.base,
tk_core.timekeeper.offs_real);
base_raw = tk->tkr_raw.base;
@@ -907,10 +910,123 @@ void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
}
EXPORT_SYMBOL_GPL(ktime_get_snapshot);
+/* Scale base by mult/div checking for overflow */
+static int scale64_check_overflow(u64 mult, u64 div, u64 *base)
+{
+ u64 tmp, rem;
+
+ tmp = div64_u64_rem(*base, div, &rem);
+
+ if (((int)sizeof(u64)*8 - fls64(mult) < fls64(tmp)) ||
+ ((int)sizeof(u64)*8 - fls64(mult) < fls64(rem)))
+ return -EOVERFLOW;
+ tmp *= mult;
+ rem *= mult;
+
+ do_div(rem, div);
+ *base = tmp + rem;
+ return 0;
+}
+
+/**
+ * adjust_historical_crosststamp - adjust crosstimestamp previous to current interval
+ * @history: Snapshot representing start of history
+ * @partial_history_cycles: Cycle offset into history (fractional part)
+ * @total_history_cycles: Total history length in cycles
+ * @discontinuity: True indicates clock was set on history period
+ * @ts: Cross timestamp that should be adjusted using
+ * partial/total ratio
+ *
+ * Helper function used by get_device_system_crosststamp() to correct the
+ * crosstimestamp corresponding to the start of the current interval to the
+ * system counter value (timestamp point) provided by the driver. The
+ * total_history_* quantities are the total history starting at the provided
+ * reference point and ending at the start of the current interval. The cycle
+ * count between the driver timestamp point and the start of the current
+ * interval is partial_history_cycles.
+ */
+static int adjust_historical_crosststamp(struct system_time_snapshot *history,
+ cycle_t partial_history_cycles,
+ cycle_t total_history_cycles,
+ bool discontinuity,
+ struct system_device_crosststamp *ts)
+{
+ struct timekeeper *tk = &tk_core.timekeeper;
+ u64 corr_raw, corr_real;
+ bool interp_forward;
+ int ret;
+
+ if (total_history_cycles == 0 || partial_history_cycles == 0)
+ return 0;
+
+ /* Interpolate shortest distance from beginning or end of history */
+ interp_forward = partial_history_cycles > total_history_cycles/2 ?
+ true : false;
+ partial_history_cycles = interp_forward ?
+ total_history_cycles - partial_history_cycles :
+ partial_history_cycles;
+
+ /*
+ * Scale the monotonic raw time delta by:
+ * partial_history_cycles / total_history_cycles
+ */
+ corr_raw = (u64)ktime_to_ns(
+ ktime_sub(ts->sys_monoraw, history->raw));
+ ret = scale64_check_overflow(partial_history_cycles,
+ total_history_cycles, &corr_raw);
+ if (ret)
+ return ret;
+
+ /*
+ * If there is a discontinuity in the history, scale monotonic raw
+ * correction by:
+ * mult(real)/mult(raw) yielding the realtime correction
+ * Otherwise, calculate the realtime correction similar to monotonic
+ * raw calculation
+ */
+ if (discontinuity) {
+ corr_real = mul_u64_u32_div
+ (corr_raw, tk->tkr_mono.mult, tk->tkr_raw.mult);
+ } else {
+ corr_real = (u64)ktime_to_ns(
+ ktime_sub(ts->sys_realtime, history->real));
+ ret = scale64_check_overflow(partial_history_cycles,
+ total_history_cycles, &corr_real);
+ if (ret)
+ return ret;
+ }
+
+ /* Fixup monotonic raw and real time time values */
+ if (interp_forward) {
+ ts->sys_monoraw = ktime_add_ns(history->raw, corr_raw);
+ ts->sys_realtime = ktime_add_ns(history->real, corr_real);
+ } else {
+ ts->sys_monoraw = ktime_sub_ns(ts->sys_monoraw, corr_raw);
+ ts->sys_realtime = ktime_sub_ns(ts->sys_realtime, corr_real);
+ }
+
+ return 0;
+}
+
+/*
+ * cycle_between - true if test occurs chronologically between before and after
+ */
+static bool cycle_between(cycle_t before, cycle_t test, cycle_t after)
+{
+ if (test > before && test < after)
+ return true;
+ if (test < before && before > after)
+ return true;
+ return false;
+}
+
/**
* get_device_system_crosststamp - Synchronously capture system/device timestamp
- * @sync_devicetime: Callback to get simultaneous device time and
+ * @get_time_fn: Callback to get simultaneous device time and
* system counter from the device driver
+ * @ctx: Context passed to get_time_fn()
+ * @history_begin: Historical reference point used to interpolate system
+ * time when counter provided by the driver is before the current interval
* @xtstamp: Receives simultaneously captured system and device time
*
* Reads a timestamp from a device and correlates it to system time
@@ -920,13 +1036,18 @@ int get_device_system_crosststamp(int (*get_time_fn)
struct system_counterval_t *sys_counterval,
void *ctx),
void *ctx,
+ struct system_time_snapshot *history_begin,
struct system_device_crosststamp *xtstamp)
{
struct system_counterval_t system_counterval;
struct timekeeper *tk = &tk_core.timekeeper;
+ cycle_t cycles, now, interval_start;
+ unsigned int clock_was_set_seq;
ktime_t base_real, base_raw;
s64 nsec_real, nsec_raw;
+ u8 cs_was_changed_seq;
unsigned long seq;
+ bool do_interp;
int ret;
do {
@@ -946,6 +1067,22 @@ int get_device_system_crosststamp(int (*get_time_fn)
*/
if (tk->tkr_mono.clock != system_counterval.cs)
return -ENODEV;
+ cycles = system_counterval.cycles;
+
+ /*
+ * Check whether the system counter value provided by the
+ * device driver is on the current timekeeping interval.
+ */
+ now = tk->tkr_mono.read(tk->tkr_mono.clock);
+ interval_start = tk->tkr_mono.cycle_last;
+ if (!cycle_between(interval_start, cycles, now)) {
+ clock_was_set_seq = tk->clock_was_set_seq;
+ cs_was_changed_seq = tk->cs_was_changed_seq;
+ cycles = interval_start;
+ do_interp = true;
+ } else {
+ do_interp = false;
+ }
base_real = ktime_add(tk->tkr_mono.base,
tk_core.timekeeper.offs_real);
@@ -959,6 +1096,38 @@ int get_device_system_crosststamp(int (*get_time_fn)
xtstamp->sys_realtime = ktime_add_ns(base_real, nsec_real);
xtstamp->sys_monoraw = ktime_add_ns(base_raw, nsec_raw);
+
+ /*
+ * Interpolate if necessary, adjusting back from the start of the
+ * current interval
+ */
+ if (do_interp) {
+ cycle_t partial_history_cycles, total_history_cycles;
+ bool discontinuity;
+
+ /*
+ * Check that the counter value occurs after the provided
+ * history reference and that the history doesn't cross a
+ * clocksource change
+ */
+ if (!history_begin ||
+ !cycle_between(history_begin->cycles,
+ system_counterval.cycles, cycles) ||
+ history_begin->cs_was_changed_seq != cs_was_changed_seq)
+ return -EINVAL;
+ partial_history_cycles = cycles - system_counterval.cycles;
+ total_history_cycles = cycles - history_begin->cycles;
+ discontinuity =
+ history_begin->clock_was_set_seq != clock_was_set_seq;
+
+ ret = adjust_historical_crosststamp(history_begin,
+ partial_history_cycles,
+ total_history_cycles,
+ discontinuity, xtstamp);
+ if (ret)
+ return ret;
+ }
+
return 0;
}
EXPORT_SYMBOL_GPL(get_device_system_crosststamp);
--
1.9.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH 6/8] x86: tsc: Always Running Timer (ART) correlated clocksource
2016-03-03 4:21 [PATCH 0/8][GIT PULL] time: Cross-timestamp infrastructure for 4.6 John Stultz
` (4 preceding siblings ...)
2016-03-03 4:21 ` [PATCH 5/8] time: Add history to cross timestamp interface supporting slower devices John Stultz
@ 2016-03-03 4:21 ` John Stultz
2016-03-03 10:21 ` Thomas Gleixner
2016-03-03 4:21 ` [PATCH 7/8] ptp: Add PTP_SYS_OFFSET_PRECISE for driver crosstimestamping John Stultz
2016-03-03 4:21 ` [PATCH 8/8] net: e1000e: Adds hardware supported cross timestamp on e1000e nic John Stultz
7 siblings, 1 reply; 14+ messages in thread
From: John Stultz @ 2016-03-03 4:21 UTC (permalink / raw)
To: lkml
Cc: Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, kevin.b.stanton,
kevin.j.clarke, hpa, jeffrey.t.kirsher, netdev, John Stultz
From: "Christopher S. Hall" <christopher.s.hall@intel.com>
On modern Intel systems TSC is derived from the new Always Running Timer
(ART). ART can be captured simultaneous to the capture of
audio and network device clocks, allowing a correlation between timebases
to be constructed. Upon capture, the driver converts the captured ART
value to the appropriate system clock using the correlated clocksource
mechanism.
On systems that support ART a new CPUID leaf (0x15) returns parameters
“m” and “n” such that:
TSC_value = (ART_value * m) / n + k [n >= 1]
[k is an offset that can adjusted by a privileged agent. The
IA32_TSC_ADJUST MSR is an example of an interface to adjust k.
See 17.14.4 of the Intel SDM for more details]
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
[jstultz: Tweaked to fix build issue, also reworked math for
64bit division on 32bit systems, as well as !CONFIG_CPU_FREQ build
fixes]
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
arch/x86/include/asm/cpufeature.h | 2 +-
arch/x86/include/asm/tsc.h | 2 ++
arch/x86/kernel/tsc.c | 62 +++++++++++++++++++++++++++++++++++++++
3 files changed, 65 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 7ad8c94..ff557b4 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -85,7 +85,7 @@
#define X86_FEATURE_P4 ( 3*32+ 7) /* "" P4 */
#define X86_FEATURE_CONSTANT_TSC ( 3*32+ 8) /* TSC ticks at a constant rate */
#define X86_FEATURE_UP ( 3*32+ 9) /* smp kernel running on up */
-/* free, was #define X86_FEATURE_FXSAVE_LEAK ( 3*32+10) * "" FXSAVE leaks FOP/FIP/FOP */
+#define X86_FEATURE_ART (3*32+10) /* Platform has always running timer (ART) */
#define X86_FEATURE_ARCH_PERFMON ( 3*32+11) /* Intel Architectural PerfMon */
#define X86_FEATURE_PEBS ( 3*32+12) /* Precise-Event Based Sampling */
#define X86_FEATURE_BTS ( 3*32+13) /* Branch Trace Store */
diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 6d7c547..174c421 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -29,6 +29,8 @@ static inline cycles_t get_cycles(void)
return rdtsc();
}
+extern struct system_counterval_t convert_art_to_tsc(cycle_t art);
+
extern void tsc_init(void);
extern void mark_tsc_unstable(char *reason);
extern int unsynchronized_tsc(void);
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 3d743da..683c8cb 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -43,6 +43,11 @@ static DEFINE_STATIC_KEY_FALSE(__use_tsc);
int tsc_clocksource_reliable;
+static u32 art_to_tsc_numerator;
+static u32 art_to_tsc_denominator;
+static u64 art_to_tsc_offset;
+struct clocksource *art_related_clocksource;
+
/*
* Use a ring-buffer like data structure, where a writer advances the head by
* writing a new data entry and a reader advances the tail when it observes a
@@ -949,6 +954,36 @@ static struct notifier_block time_cpufreq_notifier_block = {
.notifier_call = time_cpufreq_notifier
};
+#define ART_CPUID_LEAF (0x15)
+#define ART_MIN_DENOMINATOR (1)
+
+
+/*
+ * If ART is present detect the numerator:denominator to convert to TSC
+ */
+static void detect_art(void)
+{
+ unsigned int unused[2];
+
+ if (boot_cpu_data.cpuid_level < ART_CPUID_LEAF)
+ return;
+
+ cpuid(ART_CPUID_LEAF, &art_to_tsc_denominator,
+ &art_to_tsc_numerator, unused, unused+1);
+
+ /* Don't enable ART in a VM, non-stop TSC required */
+ if (boot_cpu_has(X86_FEATURE_HYPERVISOR) ||
+ !boot_cpu_has(X86_FEATURE_NONSTOP_TSC) ||
+ art_to_tsc_denominator < ART_MIN_DENOMINATOR)
+ return;
+
+ if (rdmsrl_safe(MSR_IA32_TSC_ADJUST, &art_to_tsc_offset))
+ return;
+
+ /* Make this sticky over multiple CPU init calls */
+ setup_force_cpu_cap(X86_FEATURE_ART);
+}
+
static int __init cpufreq_tsc(void)
{
if (!cpu_has_tsc)
@@ -962,6 +997,10 @@ static int __init cpufreq_tsc(void)
core_initcall(cpufreq_tsc);
+#else
+
+#define detect_art()
+
#endif /* CONFIG_CPU_FREQ */
/* clocksource code */
@@ -1071,6 +1110,25 @@ int unsynchronized_tsc(void)
return 0;
}
+/*
+ * Convert ART to TSC given numerator/denominator found in detect_art()
+ */
+struct system_counterval_t convert_art_to_tsc(cycle_t art)
+{
+ u64 tmp, res, rem;
+
+ rem = do_div(art, art_to_tsc_denominator);
+
+ res = art * art_to_tsc_numerator;
+ tmp = rem * art_to_tsc_numerator;
+
+ do_div(tmp, art_to_tsc_denominator);
+ res += tmp + art_to_tsc_offset;
+
+ return (struct system_counterval_t) {.cs = art_related_clocksource,
+ .cycles = res};
+}
+EXPORT_SYMBOL(convert_art_to_tsc);
static void tsc_refine_calibration_work(struct work_struct *work);
static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work);
@@ -1142,6 +1200,8 @@ static void tsc_refine_calibration_work(struct work_struct *work)
(unsigned long)tsc_khz % 1000);
out:
+ if (boot_cpu_has(X86_FEATURE_ART))
+ art_related_clocksource = &clocksource_tsc;
clocksource_register_khz(&clocksource_tsc, tsc_khz);
}
@@ -1235,6 +1295,8 @@ void __init tsc_init(void)
mark_tsc_unstable("TSCs unsynchronized");
check_system_tsc_reliable();
+
+ detect_art();
}
#ifdef CONFIG_SMP
--
1.9.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* Re: [PATCH 6/8] x86: tsc: Always Running Timer (ART) correlated clocksource
2016-03-03 4:21 ` [PATCH 6/8] x86: tsc: Always Running Timer (ART) correlated clocksource John Stultz
@ 2016-03-03 10:21 ` Thomas Gleixner
2016-03-03 22:24 ` John Stultz
0 siblings, 1 reply; 14+ messages in thread
From: Thomas Gleixner @ 2016-03-03 10:21 UTC (permalink / raw)
To: John Stultz
Cc: lkml, Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Ingo Molnar, Andy Lutomirski, kevin.b.stanton, kevin.j.clarke,
hpa, jeffrey.t.kirsher, netdev
On Wed, 2 Mar 2016, John Stultz wrote:
Subject: x86: tsc: Always Running ...
Please make that:
Subject: x86/tsc: Always Running ...
>
> +#else
> +
> +#define detect_art()
Inline stub if at all. Why sits detect_art() under CONFIG_CPU_FREQ while the
rest of the art code is not????
Thanks
tglx
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH 6/8] x86: tsc: Always Running Timer (ART) correlated clocksource
2016-03-03 10:21 ` Thomas Gleixner
@ 2016-03-03 22:24 ` John Stultz
0 siblings, 0 replies; 14+ messages in thread
From: John Stultz @ 2016-03-03 22:24 UTC (permalink / raw)
To: Thomas Gleixner
Cc: lkml, Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Ingo Molnar, Andy Lutomirski, Stanton, Kevin B, kevin.j.clarke,
H. Peter Anvin, Jeff Kirsher, netdev
On Thu, Mar 3, 2016 at 2:21 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Wed, 2 Mar 2016, John Stultz wrote:
>
> Subject: x86: tsc: Always Running ...
>
> Please make that:
>
> Subject: x86/tsc: Always Running ...
Will do.
>
>>
>> +#else
>> +
>> +#define detect_art()
>
> Inline stub if at all. Why sits detect_art() under CONFIG_CPU_FREQ while the
> rest of the art code is not????
Ok. Just double checked with Christopher and the code is ok to move
out from CONFIG_CPU_FREQ.
I'll respin and resend the set later today.
thanks
-john
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH 7/8] ptp: Add PTP_SYS_OFFSET_PRECISE for driver crosstimestamping
2016-03-03 4:21 [PATCH 0/8][GIT PULL] time: Cross-timestamp infrastructure for 4.6 John Stultz
` (5 preceding siblings ...)
2016-03-03 4:21 ` [PATCH 6/8] x86: tsc: Always Running Timer (ART) correlated clocksource John Stultz
@ 2016-03-03 4:21 ` John Stultz
2016-03-03 4:21 ` [PATCH 8/8] net: e1000e: Adds hardware supported cross timestamp on e1000e nic John Stultz
7 siblings, 0 replies; 14+ messages in thread
From: John Stultz @ 2016-03-03 4:21 UTC (permalink / raw)
To: lkml
Cc: Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, kevin.b.stanton,
kevin.j.clarke, hpa, jeffrey.t.kirsher, netdev, John Stultz
From: "Christopher S. Hall" <christopher.s.hall@intel.com>
Currently, network /system cross-timestamping is performed in the
PTP_SYS_OFFSET ioctl. The PTP clock driver reads gettimeofday() and
the gettime64() callback provided by the driver. The cross-timestamp
is best effort where the latency between the capture of system time
(getnstimeofday()) and the device time (driver callback) may be
significant.
The getcrosststamp() callback and corresponding PTP_SYS_OFFSET_PRECISE
ioctl allows the driver to perform this device/system correlation when
for example cross timestamp hardware is available. Modern Intel
systems can do this for onboard Ethernet controllers using the ART
counter. There is virtually zero latency between captures of the ART
and network device clock.
The capabilities ioctl (PTP_CLOCK_GETCAPS), is augmented allowing
applications to query whether or not drivers implement the
getcrosststamp callback, providing more precise cross timestamping.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
[jstultz: Commit subject tweaks]
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
Documentation/ptp/testptp.c | 6 ++++--
drivers/ptp/ptp_chardev.c | 27 +++++++++++++++++++++++++++
include/linux/ptp_clock_kernel.h | 8 ++++++++
include/uapi/linux/ptp_clock.h | 13 ++++++++++++-
4 files changed, 51 insertions(+), 3 deletions(-)
diff --git a/Documentation/ptp/testptp.c b/Documentation/ptp/testptp.c
index 6c6247a..d99012f 100644
--- a/Documentation/ptp/testptp.c
+++ b/Documentation/ptp/testptp.c
@@ -277,13 +277,15 @@ int main(int argc, char *argv[])
" %d external time stamp channels\n"
" %d programmable periodic signals\n"
" %d pulse per second\n"
- " %d programmable pins\n",
+ " %d programmable pins\n"
+ " %d cross timestamping\n",
caps.max_adj,
caps.n_alarm,
caps.n_ext_ts,
caps.n_per_out,
caps.pps,
- caps.n_pins);
+ caps.n_pins,
+ caps.cross_timestamping);
}
}
diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index da7bae9..579fd65 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -22,6 +22,7 @@
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/slab.h>
+#include <linux/timekeeping.h>
#include "ptp_private.h"
@@ -120,11 +121,13 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
struct ptp_clock_caps caps;
struct ptp_clock_request req;
struct ptp_sys_offset *sysoff = NULL;
+ struct ptp_sys_offset_precise precise_offset;
struct ptp_pin_desc pd;
struct ptp_clock *ptp = container_of(pc, struct ptp_clock, clock);
struct ptp_clock_info *ops = ptp->info;
struct ptp_clock_time *pct;
struct timespec64 ts;
+ struct system_device_crosststamp xtstamp;
int enable, err = 0;
unsigned int i, pin_index;
@@ -138,6 +141,7 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
caps.n_per_out = ptp->info->n_per_out;
caps.pps = ptp->info->pps;
caps.n_pins = ptp->info->n_pins;
+ caps.cross_timestamping = ptp->info->getcrosststamp != NULL;
if (copy_to_user((void __user *)arg, &caps, sizeof(caps)))
err = -EFAULT;
break;
@@ -180,6 +184,29 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
err = ops->enable(ops, &req, enable);
break;
+ case PTP_SYS_OFFSET_PRECISE:
+ if (!ptp->info->getcrosststamp) {
+ err = -EOPNOTSUPP;
+ break;
+ }
+ err = ptp->info->getcrosststamp(ptp->info, &xtstamp);
+ if (err)
+ break;
+
+ ts = ktime_to_timespec64(xtstamp.device);
+ precise_offset.device.sec = ts.tv_sec;
+ precise_offset.device.nsec = ts.tv_nsec;
+ ts = ktime_to_timespec64(xtstamp.sys_realtime);
+ precise_offset.sys_realtime.sec = ts.tv_sec;
+ precise_offset.sys_realtime.nsec = ts.tv_nsec;
+ ts = ktime_to_timespec64(xtstamp.sys_monoraw);
+ precise_offset.sys_monoraw.sec = ts.tv_sec;
+ precise_offset.sys_monoraw.nsec = ts.tv_nsec;
+ if (copy_to_user((void __user *)arg, &precise_offset,
+ sizeof(precise_offset)))
+ err = -EFAULT;
+ break;
+
case PTP_SYS_OFFSET:
sysoff = kmalloc(sizeof(*sysoff), GFP_KERNEL);
if (!sysoff) {
diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h
index b8b7306..6b15e16 100644
--- a/include/linux/ptp_clock_kernel.h
+++ b/include/linux/ptp_clock_kernel.h
@@ -38,6 +38,7 @@ struct ptp_clock_request {
};
};
+struct system_device_crosststamp;
/**
* struct ptp_clock_info - decribes a PTP hardware clock
*
@@ -67,6 +68,11 @@ struct ptp_clock_request {
* @gettime64: Reads the current time from the hardware clock.
* parameter ts: Holds the result.
*
+ * @getcrosststamp: Reads the current time from the hardware clock and
+ * system clock simultaneously.
+ * parameter cts: Contains timestamp (device,system) pair,
+ * where system time is realtime and monotonic.
+ *
* @settime64: Set the current time on the hardware clock.
* parameter ts: Time value to set.
*
@@ -105,6 +111,8 @@ struct ptp_clock_info {
int (*adjfreq)(struct ptp_clock_info *ptp, s32 delta);
int (*adjtime)(struct ptp_clock_info *ptp, s64 delta);
int (*gettime64)(struct ptp_clock_info *ptp, struct timespec64 *ts);
+ int (*getcrosststamp)(struct ptp_clock_info *ptp,
+ struct system_device_crosststamp *cts);
int (*settime64)(struct ptp_clock_info *p, const struct timespec64 *ts);
int (*enable)(struct ptp_clock_info *ptp,
struct ptp_clock_request *request, int on);
diff --git a/include/uapi/linux/ptp_clock.h b/include/uapi/linux/ptp_clock.h
index f0b7bfe..ac6dded 100644
--- a/include/uapi/linux/ptp_clock.h
+++ b/include/uapi/linux/ptp_clock.h
@@ -51,7 +51,9 @@ struct ptp_clock_caps {
int n_per_out; /* Number of programmable periodic signals. */
int pps; /* Whether the clock supports a PPS callback. */
int n_pins; /* Number of input/output pins. */
- int rsv[14]; /* Reserved for future use. */
+ /* Whether the clock supports precise system-device cross timestamps */
+ int cross_timestamping;
+ int rsv[13]; /* Reserved for future use. */
};
struct ptp_extts_request {
@@ -81,6 +83,13 @@ struct ptp_sys_offset {
struct ptp_clock_time ts[2 * PTP_MAX_SAMPLES + 1];
};
+struct ptp_sys_offset_precise {
+ struct ptp_clock_time device;
+ struct ptp_clock_time sys_realtime;
+ struct ptp_clock_time sys_monoraw;
+ unsigned int rsv[4]; /* Reserved for future use. */
+};
+
enum ptp_pin_function {
PTP_PF_NONE,
PTP_PF_EXTTS,
@@ -124,6 +133,8 @@ struct ptp_pin_desc {
#define PTP_SYS_OFFSET _IOW(PTP_CLK_MAGIC, 5, struct ptp_sys_offset)
#define PTP_PIN_GETFUNC _IOWR(PTP_CLK_MAGIC, 6, struct ptp_pin_desc)
#define PTP_PIN_SETFUNC _IOW(PTP_CLK_MAGIC, 7, struct ptp_pin_desc)
+#define PTP_SYS_OFFSET_PRECISE \
+ _IOWR(PTP_CLK_MAGIC, 8, struct ptp_sys_offset_precise)
struct ptp_extts_event {
struct ptp_clock_time t; /* Time event occured. */
--
1.9.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* [PATCH 8/8] net: e1000e: Adds hardware supported cross timestamp on e1000e nic
2016-03-03 4:21 [PATCH 0/8][GIT PULL] time: Cross-timestamp infrastructure for 4.6 John Stultz
` (6 preceding siblings ...)
2016-03-03 4:21 ` [PATCH 7/8] ptp: Add PTP_SYS_OFFSET_PRECISE for driver crosstimestamping John Stultz
@ 2016-03-03 4:21 ` John Stultz
2016-03-03 22:27 ` Jeff Kirsher
7 siblings, 1 reply; 14+ messages in thread
From: John Stultz @ 2016-03-03 4:21 UTC (permalink / raw)
To: lkml
Cc: Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, Jeff Kirsher,
kevin.b.stanton, kevin.j.clarke, hpa, netdev, John Stultz
From: "Christopher S. Hall" <christopher.s.hall@intel.com>
Modern Intel systems supports cross timestamping of the network device
clock and Always Running Timer (ART) in hardware. This allows the
device time and system time to be precisely correlated. The timestamp
pair is returned through e1000e_phc_get_syncdevicetime() used by
get_system_device_crosststamp(). The hardware cross-timestamp result
is made available to applications through the PTP_SYS_OFFSET_PRECISE
ioctl which calls e1000e_phc_getcrosststamp().
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
[jstultz: Reworked to use new interface, commit message tweaks]
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
drivers/net/ethernet/intel/Kconfig | 9 +++
drivers/net/ethernet/intel/e1000e/defines.h | 5 ++
drivers/net/ethernet/intel/e1000e/ptp.c | 85 +++++++++++++++++++++++++++++
drivers/net/ethernet/intel/e1000e/regs.h | 4 ++
4 files changed, 103 insertions(+)
diff --git a/drivers/net/ethernet/intel/Kconfig b/drivers/net/ethernet/intel/Kconfig
index fa593dd..3772f3a 100644
--- a/drivers/net/ethernet/intel/Kconfig
+++ b/drivers/net/ethernet/intel/Kconfig
@@ -83,6 +83,15 @@ config E1000E
To compile this driver as a module, choose M here. The module
will be called e1000e.
+config E1000E_HWTS
+ bool "Support HW cross-timestamp on PCH devices"
+ default y
+ depends on E1000E && X86
+ ---help---
+ Say Y to enable hardware supported cross-timestamping on PCH
+ devices. The cross-timestamp is available through the PTP clock
+ driver precise cross-timestamp ioctl (PTP_SYS_OFFSET_PRECISE).
+
config IGB
tristate "Intel(R) 82575/82576 PCI-Express Gigabit Ethernet support"
depends on PCI
diff --git a/drivers/net/ethernet/intel/e1000e/defines.h b/drivers/net/ethernet/intel/e1000e/defines.h
index f7c7804..0641c00 100644
--- a/drivers/net/ethernet/intel/e1000e/defines.h
+++ b/drivers/net/ethernet/intel/e1000e/defines.h
@@ -528,6 +528,11 @@
#define E1000_RXCW_C 0x20000000 /* Receive config */
#define E1000_RXCW_SYNCH 0x40000000 /* Receive config synch */
+/* HH Time Sync */
+#define E1000_TSYNCTXCTL_MAX_ALLOWED_DLY_MASK 0x0000F000 /* max delay */
+#define E1000_TSYNCTXCTL_SYNC_COMP 0x40000000 /* sync complete */
+#define E1000_TSYNCTXCTL_START_SYNC 0x80000000 /* initiate sync */
+
#define E1000_TSYNCTXCTL_VALID 0x00000001 /* Tx timestamp valid */
#define E1000_TSYNCTXCTL_ENABLED 0x00000010 /* enable Tx timestamping */
diff --git a/drivers/net/ethernet/intel/e1000e/ptp.c b/drivers/net/ethernet/intel/e1000e/ptp.c
index 25a0ad5..e2ff3ef 100644
--- a/drivers/net/ethernet/intel/e1000e/ptp.c
+++ b/drivers/net/ethernet/intel/e1000e/ptp.c
@@ -26,6 +26,12 @@
#include "e1000.h"
+#ifdef CONFIG_E1000E_HWTS
+#include <linux/clocksource.h>
+#include <linux/ktime.h>
+#include <asm/tsc.h>
+#endif
+
/**
* e1000e_phc_adjfreq - adjust the frequency of the hardware clock
* @ptp: ptp clock structure
@@ -98,6 +104,78 @@ static int e1000e_phc_adjtime(struct ptp_clock_info *ptp, s64 delta)
return 0;
}
+#ifdef CONFIG_E1000E_HWTS
+#define MAX_HW_WAIT_COUNT (3)
+
+/**
+ * e1000e_phc_get_syncdevicetime - Callback given to timekeeping code reads system/device registers
+ * @device: current device time
+ * @system: system counter value read synchronously with device time
+ * @ctx: context provided by timekeeping code
+ *
+ * Read device and system (ART) clock simultaneously and return the corrected
+ * clock values in ns.
+ **/
+static int e1000e_phc_get_syncdevicetime(ktime_t *device,
+ struct system_counterval_t *system,
+ void *ctx)
+{
+ struct e1000_adapter *adapter = (struct e1000_adapter *)ctx;
+ struct e1000_hw *hw = &adapter->hw;
+ unsigned long flags;
+ int i;
+ u32 tsync_ctrl;
+ cycle_t dev_cycles;
+ cycle_t sys_cycles;
+
+ tsync_ctrl = er32(TSYNCTXCTL);
+ tsync_ctrl |= E1000_TSYNCTXCTL_START_SYNC |
+ E1000_TSYNCTXCTL_MAX_ALLOWED_DLY_MASK;
+ ew32(TSYNCTXCTL, tsync_ctrl);
+ for (i = 0; i < MAX_HW_WAIT_COUNT; ++i) {
+ udelay(1);
+ tsync_ctrl = er32(TSYNCTXCTL);
+ if (tsync_ctrl & E1000_TSYNCTXCTL_SYNC_COMP)
+ break;
+ }
+
+ if (i == MAX_HW_WAIT_COUNT)
+ return -ETIMEDOUT;
+
+ dev_cycles = er32(SYSSTMPH);
+ dev_cycles <<= 32;
+ dev_cycles |= er32(SYSSTMPL);
+ spin_lock_irqsave(&adapter->systim_lock, flags);
+ *device = ns_to_ktime(timecounter_cyc2time(&adapter->tc, dev_cycles));
+ spin_unlock_irqrestore(&adapter->systim_lock, flags);
+
+ sys_cycles = er32(PLTSTMPH);
+ sys_cycles <<= 32;
+ sys_cycles |= er32(PLTSTMPL);
+ *system = convert_art_to_tsc(sys_cycles);
+
+ return 0;
+}
+
+/**
+ * e1000e_phc_getsynctime - Reads the current system/device cross timestamp
+ * @ptp: ptp clock structure
+ * @cts: structure containing timestamp
+ *
+ * Read device and system (ART) clock simultaneously and return the scaled
+ * clock values in ns.
+ **/
+static int e1000e_phc_getcrosststamp(struct ptp_clock_info *ptp,
+ struct system_device_crosststamp *xtstamp)
+{
+ struct e1000_adapter *adapter = container_of(ptp, struct e1000_adapter,
+ ptp_clock_info);
+
+ return get_device_system_crosststamp(e1000e_phc_get_syncdevicetime,
+ adapter, NULL, xtstamp);
+}
+#endif/*CONFIG_E1000E_HWTS*/
+
/**
* e1000e_phc_gettime - Reads the current time from the hardware clock
* @ptp: ptp clock structure
@@ -236,6 +314,13 @@ void e1000e_ptp_init(struct e1000_adapter *adapter)
break;
}
+#ifdef CONFIG_E1000E_HWTS
+ /* CPU must have ART and GBe must be from Sunrise Point or greater */
+ if (hw->mac.type >= e1000_pch_spt && boot_cpu_has(X86_FEATURE_ART))
+ adapter->ptp_clock_info.getcrosststamp =
+ e1000e_phc_getcrosststamp;
+#endif/*CONFIG_E1000E_HWTS*/
+
INIT_DELAYED_WORK(&adapter->systim_overflow_work,
e1000e_systim_overflow_work);
diff --git a/drivers/net/ethernet/intel/e1000e/regs.h b/drivers/net/ethernet/intel/e1000e/regs.h
index 1d5e0b7..0cb4d36 100644
--- a/drivers/net/ethernet/intel/e1000e/regs.h
+++ b/drivers/net/ethernet/intel/e1000e/regs.h
@@ -245,6 +245,10 @@
#define E1000_SYSTIML 0x0B600 /* System time register Low - RO */
#define E1000_SYSTIMH 0x0B604 /* System time register High - RO */
#define E1000_TIMINCA 0x0B608 /* Increment attributes register - RW */
+#define E1000_SYSSTMPL 0x0B648 /* HH Timesync system stamp low register */
+#define E1000_SYSSTMPH 0x0B64C /* HH Timesync system stamp hi register */
+#define E1000_PLTSTMPL 0x0B640 /* HH Timesync platform stamp low register */
+#define E1000_PLTSTMPH 0x0B644 /* HH Timesync platform stamp hi register */
#define E1000_RXMTRL 0x0B634 /* Time sync Rx EtherType and Msg Type - RW */
#define E1000_RXUDP 0x0B638 /* Time Sync Rx UDP Port - RW */
--
1.9.1
^ permalink raw reply related [flat|nested] 14+ messages in thread* Re: [PATCH 8/8] net: e1000e: Adds hardware supported cross timestamp on e1000e nic
2016-03-03 4:21 ` [PATCH 8/8] net: e1000e: Adds hardware supported cross timestamp on e1000e nic John Stultz
@ 2016-03-03 22:27 ` Jeff Kirsher
2016-03-03 22:29 ` John Stultz
0 siblings, 1 reply; 14+ messages in thread
From: Jeff Kirsher @ 2016-03-03 22:27 UTC (permalink / raw)
To: John Stultz, lkml
Cc: Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, kevin.b.stanton,
kevin.j.clarke, hpa, netdev
[-- Attachment #1: Type: text/plain, Size: 1764 bytes --]
On Wed, 2016-03-02 at 20:21 -0800, John Stultz wrote:
> From: "Christopher S. Hall" <christopher.s.hall@intel.com>
>
> Modern Intel systems supports cross timestamping of the network
> device
> clock and Always Running Timer (ART) in hardware. This allows the
> device time and system time to be precisely correlated. The timestamp
> pair is returned through e1000e_phc_get_syncdevicetime() used by
> get_system_device_crosststamp(). The hardware cross-timestamp result
> is made available to applications through the PTP_SYS_OFFSET_PRECISE
> ioctl which calls e1000e_phc_getcrosststamp().
>
> Cc: Prarit Bhargava <prarit@redhat.com>
> Cc: Richard Cochran <richardcochran@gmail.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> Cc: kevin.b.stanton@intel.com
> Cc: kevin.j.clarke@intel.com
> Cc: hpa@zytor.com
> Cc: jeffrey.t.kirsher@intel.com
> Cc: netdev@vger.kernel.org
> Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
> [jstultz: Reworked to use new interface, commit message tweaks]
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> ---
> drivers/net/ethernet/intel/Kconfig | 9 +++
> drivers/net/ethernet/intel/e1000e/defines.h | 5 ++
> drivers/net/ethernet/intel/e1000e/ptp.c | 85
> +++++++++++++++++++++++++++++
> drivers/net/ethernet/intel/e1000e/regs.h | 4 ++
> 4 files changed, 103 insertions(+)
Since you are making changes to patch 6's title, then you should fix
this patch title as well, it should be:
[PATCH 8/8] e1000e: Adds hardware supported...
[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 819 bytes --]
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH 8/8] net: e1000e: Adds hardware supported cross timestamp on e1000e nic
2016-03-03 22:27 ` Jeff Kirsher
@ 2016-03-03 22:29 ` John Stultz
0 siblings, 0 replies; 14+ messages in thread
From: John Stultz @ 2016-03-03 22:29 UTC (permalink / raw)
To: Jeff Kirsher
Cc: lkml, Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, Stanton, Kevin B,
kevin.j.clarke, H. Peter Anvin, netdev
On Thu, Mar 3, 2016 at 2:27 PM, Jeff Kirsher
<jeffrey.t.kirsher@intel.com> wrote:
> Since you are making changes to patch 6's title, then you should fix
> this patch title as well, it should be:
>
> [PATCH 8/8] e1000e: Adds hardware supported...
Ack
-john
^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH 5/8] time: Add history to cross timestamp interface supporting slower devices
2016-03-04 1:56 [PATCHv2 0/8][GIT PULLv2] time: Cross-timestamp infrastructure for 4.6 John Stultz
@ 2016-03-04 1:57 ` John Stultz
0 siblings, 0 replies; 14+ messages in thread
From: John Stultz @ 2016-03-04 1:57 UTC (permalink / raw)
To: lkml
Cc: Christopher S. Hall, Prarit Bhargava, Richard Cochran,
Thomas Gleixner, Ingo Molnar, Andy Lutomirski, kevin.b.stanton,
kevin.j.clarke, hpa, jeffrey.t.kirsher, netdev, John Stultz
From: "Christopher S. Hall" <christopher.s.hall@intel.com>
Another representative use case of time sync and the correlated
clocksource (in addition to PTP noted above) is PTP synchronized
audio.
In a streaming application, as an example, samples will be sent and/or
received by multiple devices with a presentation time that is in terms
of the PTP master clock. Synchronizing the audio output on these
devices requires correlating the audio clock with the PTP master
clock. The more precise this correlation is, the better the audio
quality (i.e. out of sync audio sounds bad).
>From an application standpoint, to correlate the PTP master clock with
the audio device clock, the system clock is used as a intermediate
timebase. The transforms such an application would perform are:
System Clock <-> Audio clock
System Clock <-> Network Device Clock [<-> PTP Master Clock]
Modern Intel platforms can perform a more accurate cross timestamp in
hardware (ART,audio device clock). The audio driver requires
ART->system time transforms -- the same as required for the network
driver. These platforms offload audio processing (including
cross-timestamps) to a DSP which to ensure uninterrupted audio
processing, communicates and response to the host only once every
millsecond. As a result is takes up to a millisecond for the DSP to
receive a request, the request is processed by the DSP, the audio
output hardware is polled for completion, the result is copied into
shared memory, and the host is notified. All of these operation occur
on a millisecond cadence. This transaction requires about 2 ms, but
under heavier workloads it may take up to 4 ms.
Adding a history allows these slow devices the option of providing an
ART value outside of the current interval. In this case, the callback
provided is an accessor function for the previously obtained counter
value. If get_system_device_crosststamp() receives a counter value
previous to cycle_last, it consults the history provided as an
argument in history_ref and interpolates the realtime and monotonic
raw system time using the provided counter value. If there are any
clock discontinuities, e.g. from calling settimeofday(), the monotonic
raw time is interpolated in the usual way, but the realtime clock time
is adjusted by scaling the monotonic raw adjustment.
When an accessor function is used a history argument *must* be
provided. The history is initialized using ktime_get_snapshot() and
must be called before the counter values are read.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
[jstultz: Fixed up cycles_t/cycle_t type confusion]
Signed-off-by: John Stultz <john.stultz@linaro.org>
---
include/linux/timekeeper_internal.h | 2 +
include/linux/timekeeping.h | 5 ++
kernel/time/timekeeping.c | 171 +++++++++++++++++++++++++++++++++++-
3 files changed, 177 insertions(+), 1 deletion(-)
diff --git a/include/linux/timekeeper_internal.h b/include/linux/timekeeper_internal.h
index 2524722..e880054 100644
--- a/include/linux/timekeeper_internal.h
+++ b/include/linux/timekeeper_internal.h
@@ -50,6 +50,7 @@ struct tk_read_base {
* @offs_tai: Offset clock monotonic -> clock tai
* @tai_offset: The current UTC to TAI offset in seconds
* @clock_was_set_seq: The sequence number of clock was set events
+ * @cs_was_changed_seq: The sequence number of clocksource change events
* @next_leap_ktime: CLOCK_MONOTONIC time value of a pending leap-second
* @raw_time: Monotonic raw base time in timespec64 format
* @cycle_interval: Number of clock cycles in one NTP interval
@@ -91,6 +92,7 @@ struct timekeeper {
ktime_t offs_tai;
s32 tai_offset;
unsigned int clock_was_set_seq;
+ u8 cs_was_changed_seq;
ktime_t next_leap_ktime;
struct timespec64 raw_time;
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 4a2ca65..96f37be 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -272,11 +272,15 @@ extern void ktime_get_raw_and_real_ts64(struct timespec64 *ts_raw,
* @cycles: Clocksource counter value to produce the system times
* @real: Realtime system time
* @raw: Monotonic raw system time
+ * @clock_was_set_seq: The sequence number of clock was set events
+ * @cs_was_changed_seq: The sequence number of clocksource change events
*/
struct system_time_snapshot {
cycle_t cycles;
ktime_t real;
ktime_t raw;
+ unsigned int clock_was_set_seq;
+ u8 cs_was_changed_seq;
};
/*
@@ -312,6 +316,7 @@ extern int get_device_system_crosststamp(
struct system_counterval_t *system_counterval,
void *ctx),
void *ctx,
+ struct system_time_snapshot *history,
struct system_device_crosststamp *xtstamp);
/*
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index dba595c..931b0b1 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -233,6 +233,7 @@ static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
u64 tmp, ntpinterval;
struct clocksource *old_clock;
+ ++tk->cs_was_changed_seq;
old_clock = tk->tkr_mono.clock;
tk->tkr_mono.clock = clock;
tk->tkr_mono.read = clock->read;
@@ -894,6 +895,8 @@ void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
seq = read_seqcount_begin(&tk_core.seq);
now = tk->tkr_mono.read(tk->tkr_mono.clock);
+ systime_snapshot->cs_was_changed_seq = tk->cs_was_changed_seq;
+ systime_snapshot->clock_was_set_seq = tk->clock_was_set_seq;
base_real = ktime_add(tk->tkr_mono.base,
tk_core.timekeeper.offs_real);
base_raw = tk->tkr_raw.base;
@@ -907,10 +910,123 @@ void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot)
}
EXPORT_SYMBOL_GPL(ktime_get_snapshot);
+/* Scale base by mult/div checking for overflow */
+static int scale64_check_overflow(u64 mult, u64 div, u64 *base)
+{
+ u64 tmp, rem;
+
+ tmp = div64_u64_rem(*base, div, &rem);
+
+ if (((int)sizeof(u64)*8 - fls64(mult) < fls64(tmp)) ||
+ ((int)sizeof(u64)*8 - fls64(mult) < fls64(rem)))
+ return -EOVERFLOW;
+ tmp *= mult;
+ rem *= mult;
+
+ do_div(rem, div);
+ *base = tmp + rem;
+ return 0;
+}
+
+/**
+ * adjust_historical_crosststamp - adjust crosstimestamp previous to current interval
+ * @history: Snapshot representing start of history
+ * @partial_history_cycles: Cycle offset into history (fractional part)
+ * @total_history_cycles: Total history length in cycles
+ * @discontinuity: True indicates clock was set on history period
+ * @ts: Cross timestamp that should be adjusted using
+ * partial/total ratio
+ *
+ * Helper function used by get_device_system_crosststamp() to correct the
+ * crosstimestamp corresponding to the start of the current interval to the
+ * system counter value (timestamp point) provided by the driver. The
+ * total_history_* quantities are the total history starting at the provided
+ * reference point and ending at the start of the current interval. The cycle
+ * count between the driver timestamp point and the start of the current
+ * interval is partial_history_cycles.
+ */
+static int adjust_historical_crosststamp(struct system_time_snapshot *history,
+ cycle_t partial_history_cycles,
+ cycle_t total_history_cycles,
+ bool discontinuity,
+ struct system_device_crosststamp *ts)
+{
+ struct timekeeper *tk = &tk_core.timekeeper;
+ u64 corr_raw, corr_real;
+ bool interp_forward;
+ int ret;
+
+ if (total_history_cycles == 0 || partial_history_cycles == 0)
+ return 0;
+
+ /* Interpolate shortest distance from beginning or end of history */
+ interp_forward = partial_history_cycles > total_history_cycles/2 ?
+ true : false;
+ partial_history_cycles = interp_forward ?
+ total_history_cycles - partial_history_cycles :
+ partial_history_cycles;
+
+ /*
+ * Scale the monotonic raw time delta by:
+ * partial_history_cycles / total_history_cycles
+ */
+ corr_raw = (u64)ktime_to_ns(
+ ktime_sub(ts->sys_monoraw, history->raw));
+ ret = scale64_check_overflow(partial_history_cycles,
+ total_history_cycles, &corr_raw);
+ if (ret)
+ return ret;
+
+ /*
+ * If there is a discontinuity in the history, scale monotonic raw
+ * correction by:
+ * mult(real)/mult(raw) yielding the realtime correction
+ * Otherwise, calculate the realtime correction similar to monotonic
+ * raw calculation
+ */
+ if (discontinuity) {
+ corr_real = mul_u64_u32_div
+ (corr_raw, tk->tkr_mono.mult, tk->tkr_raw.mult);
+ } else {
+ corr_real = (u64)ktime_to_ns(
+ ktime_sub(ts->sys_realtime, history->real));
+ ret = scale64_check_overflow(partial_history_cycles,
+ total_history_cycles, &corr_real);
+ if (ret)
+ return ret;
+ }
+
+ /* Fixup monotonic raw and real time time values */
+ if (interp_forward) {
+ ts->sys_monoraw = ktime_add_ns(history->raw, corr_raw);
+ ts->sys_realtime = ktime_add_ns(history->real, corr_real);
+ } else {
+ ts->sys_monoraw = ktime_sub_ns(ts->sys_monoraw, corr_raw);
+ ts->sys_realtime = ktime_sub_ns(ts->sys_realtime, corr_real);
+ }
+
+ return 0;
+}
+
+/*
+ * cycle_between - true if test occurs chronologically between before and after
+ */
+static bool cycle_between(cycle_t before, cycle_t test, cycle_t after)
+{
+ if (test > before && test < after)
+ return true;
+ if (test < before && before > after)
+ return true;
+ return false;
+}
+
/**
* get_device_system_crosststamp - Synchronously capture system/device timestamp
- * @sync_devicetime: Callback to get simultaneous device time and
+ * @get_time_fn: Callback to get simultaneous device time and
* system counter from the device driver
+ * @ctx: Context passed to get_time_fn()
+ * @history_begin: Historical reference point used to interpolate system
+ * time when counter provided by the driver is before the current interval
* @xtstamp: Receives simultaneously captured system and device time
*
* Reads a timestamp from a device and correlates it to system time
@@ -920,13 +1036,18 @@ int get_device_system_crosststamp(int (*get_time_fn)
struct system_counterval_t *sys_counterval,
void *ctx),
void *ctx,
+ struct system_time_snapshot *history_begin,
struct system_device_crosststamp *xtstamp)
{
struct system_counterval_t system_counterval;
struct timekeeper *tk = &tk_core.timekeeper;
+ cycle_t cycles, now, interval_start;
+ unsigned int clock_was_set_seq;
ktime_t base_real, base_raw;
s64 nsec_real, nsec_raw;
+ u8 cs_was_changed_seq;
unsigned long seq;
+ bool do_interp;
int ret;
do {
@@ -946,6 +1067,22 @@ int get_device_system_crosststamp(int (*get_time_fn)
*/
if (tk->tkr_mono.clock != system_counterval.cs)
return -ENODEV;
+ cycles = system_counterval.cycles;
+
+ /*
+ * Check whether the system counter value provided by the
+ * device driver is on the current timekeeping interval.
+ */
+ now = tk->tkr_mono.read(tk->tkr_mono.clock);
+ interval_start = tk->tkr_mono.cycle_last;
+ if (!cycle_between(interval_start, cycles, now)) {
+ clock_was_set_seq = tk->clock_was_set_seq;
+ cs_was_changed_seq = tk->cs_was_changed_seq;
+ cycles = interval_start;
+ do_interp = true;
+ } else {
+ do_interp = false;
+ }
base_real = ktime_add(tk->tkr_mono.base,
tk_core.timekeeper.offs_real);
@@ -959,6 +1096,38 @@ int get_device_system_crosststamp(int (*get_time_fn)
xtstamp->sys_realtime = ktime_add_ns(base_real, nsec_real);
xtstamp->sys_monoraw = ktime_add_ns(base_raw, nsec_raw);
+
+ /*
+ * Interpolate if necessary, adjusting back from the start of the
+ * current interval
+ */
+ if (do_interp) {
+ cycle_t partial_history_cycles, total_history_cycles;
+ bool discontinuity;
+
+ /*
+ * Check that the counter value occurs after the provided
+ * history reference and that the history doesn't cross a
+ * clocksource change
+ */
+ if (!history_begin ||
+ !cycle_between(history_begin->cycles,
+ system_counterval.cycles, cycles) ||
+ history_begin->cs_was_changed_seq != cs_was_changed_seq)
+ return -EINVAL;
+ partial_history_cycles = cycles - system_counterval.cycles;
+ total_history_cycles = cycles - history_begin->cycles;
+ discontinuity =
+ history_begin->clock_was_set_seq != clock_was_set_seq;
+
+ ret = adjust_historical_crosststamp(history_begin,
+ partial_history_cycles,
+ total_history_cycles,
+ discontinuity, xtstamp);
+ if (ret)
+ return ret;
+ }
+
return 0;
}
EXPORT_SYMBOL_GPL(get_device_system_crosststamp);
--
1.9.1
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