This patchset adds a complete solution (well, the kernel part) for fast
high-precision time synchronization between computers using their LPT
ports. My tests show that it is able to achieve synchronization in the
order of 1-2 microseconds and keep it for as long as needed. We are
using this facility in my company for distributed real-time simulation.
The idea is to have a single master computer whose local clock is used
as a standard. It then provides time information through both PPS
high-precision signal over LPT and NTP over network. Then any other
computer can combine these two time sources (this is what ntpd can do).
Client-side ntpd constantly checks that the local time divergence from
the master's time is less then 128ms. If this is true it uses PPS
signal to further decrease the difference. ntpd can try to do itself
but it's too slow and imprecise. This is really a job for the kernel.
All stuff related to the PPS signals in Linux kernel is handled by the
code from LinuxPPS project. It can be controlled from user-space
through PPSAPI (RFC 2783) and ntpd can use it to pass control over
synchronization to the kernel. Unfortunately this is an optional
feature of PPSAPI and it was not implemented. Also Linux code from
NTPv4 reference model was missing all the pieces that deal with PPS.
This patchset closes both gaps to achieve the highest precision and
speed. It:
* adds missing hardpps() function to the NTPv4 Linux kernel code
* adds getnstime_raw_and_real() to atomically get both MONOTONIC_RAW
and REALTIME clock timestamps for hardpps()
* adds missing optional PPSAPI method to bind the particular PPS
source to feed information to the time subsystem through hardpps()
Also it adds the actual parallel port PPS generator and client.
This patchset is tested against the vanilla 2.6.32.9 kernel. But we are
actually using it on 2.6.31.12-rt20 rt-preempt kernel most of the time.
Also there is a version which should be applied on top of LinuxPPS out
of tree patches (i.e. all clients and low-level irq timestamps stuff).
Those who are interested in other versions of the patchset can find
them in my git repository:
http://lvk.cs.msu.su/~lasaine/timesync/linux-2.6-timesync.git
There is one problem however: hardpps() works bad when used on top
of 2.6.33-rc* with CONFIG_NO_HZ enabled. The reason for this is commit
a092ff0f90cae22b2ac8028ecd2c6f6c1a9e4601. Without it hardpps() is able
to sync to 1us precision in about 10 seconds. With it
Changelog
v1 -> v2:
* fix issues pointed out by John Stultz:
* style fixes
* add a about the authorship of the original code
* replace timespec with pps_normtime struct where timespec is used
in a wrong way
* fix seqlock usage in hardpps()
* unbind kernel consumer on device removal
* send raw timestamp instead of the last difference to hardpps() which
simplifies the code and is less error-prone
* update comments in the kernel consumer code to match the reality
* split the patch that adds MONOTONIC_RAW timestmaps into two
* other small fixes
Alexander Gordeev (6):
ntp: add hardpps implementation
pps: unify timestamp gathering
pps: capture MONOTONIC_RAW timestamps as well
pps: add kernel consumer support
pps: add parallel port PPS signal generator
pps: add parallel port PPS client
Documentation/ioctl/ioctl-number.txt | 2 +-
drivers/pps/Kconfig | 5 +
drivers/pps/Makefile | 1 +
drivers/pps/clients/Kconfig | 16 ++
drivers/pps/clients/Makefile | 9 +
drivers/pps/clients/pps_parport.c | 211 +++++++++++++++
drivers/pps/generators/Kconfig | 17 ++
drivers/pps/generators/Makefile | 9 +
drivers/pps/generators/pps_gen_parport.c | 264 +++++++++++++++++++
drivers/pps/kapi.c | 41 +++-
drivers/pps/pps.c | 67 +++++-
include/linux/pps.h | 7 +
include/linux/pps_kernel.h | 30 ++-
include/linux/time.h | 2 +
include/linux/timex.h | 1 +
kernel/time/Kconfig | 7 +
kernel/time/ntp.c | 420 ++++++++++++++++++++++++++++-
kernel/time/timekeeping.c | 34 +++
18 files changed, 1119 insertions(+), 24 deletions(-)
create mode 100644 drivers/pps/clients/Kconfig
create mode 100644 drivers/pps/clients/Makefile
create mode 100644 drivers/pps/clients/pps_parport.c
create mode 100644 drivers/pps/generators/Kconfig
create mode 100644 drivers/pps/generators/Makefile
create mode 100644 drivers/pps/generators/pps_gen_parport.c
MONOTONIC_RAW clock timestamps are ideally suited for frequency
calculation and also fit well into the original NTP hardpps design. Now
phase and frequency can be adjusted separately: the former based on
REALTIME clock and the latter based on MONOTONIC_RAW clock.
A new function getnstime_raw_and_real is added to timekeeping subsystem
to capture both timestamps at the same time and atomically.
Signed-off-by: Alexander Gordeev <[email protected]>
---
include/linux/pps_kernel.h | 3 ++-
include/linux/time.h | 2 ++
kernel/time/timekeeping.c | 34 ++++++++++++++++++++++++++++++++++
3 files changed, 38 insertions(+), 1 deletions(-)
diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
index a2804c1..9bda892 100644
--- a/include/linux/pps_kernel.h
+++ b/include/linux/pps_kernel.h
@@ -41,6 +41,7 @@ struct pps_source_info {
};
struct pps_event_time {
+ struct timespec ts_raw;
struct pps_ktime ts_real;
};
@@ -104,7 +105,7 @@ static inline void pps_get_ts(struct pps_event_time *ts)
{
struct timespec ts_real;
- getnstimeofday(&ts_real);
+ getnstime_raw_and_real(&ts->ts_raw, &ts_real);
timespec_to_pps_ktime(&ts->ts_real, ts_real);
}
diff --git a/include/linux/time.h b/include/linux/time.h
index 6e026e4..edf7eb7 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -143,6 +143,8 @@ extern unsigned int alarm_setitimer(unsigned int seconds);
extern int do_getitimer(int which, struct itimerval *value);
extern void getnstimeofday(struct timespec *tv);
extern void getrawmonotonic(struct timespec *ts);
+extern void getnstime_raw_and_real(struct timespec *ts_raw,
+ struct timespec *ts_real);
extern void getboottime(struct timespec *ts);
extern void monotonic_to_bootbased(struct timespec *ts);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 8b709de..0ca8336 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -293,6 +293,40 @@ void ktime_get_ts(struct timespec *ts)
EXPORT_SYMBOL_GPL(ktime_get_ts);
/**
+ * getnstime_raw_and_real - Returns both the time of day an raw
+ * monotonic time in a timespec format
+ * @ts_mono_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
+ */
+void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real)
+{
+ unsigned long seq;
+ s64 nsecs_raw, nsecs_real;
+
+ WARN_ON(timekeeping_suspended);
+
+ do {
+ seq = read_seqbegin(&xtime_lock);
+
+ *ts_raw = raw_time;
+ *ts_real = xtime;
+
+ nsecs_raw = timekeeping_get_ns_raw();
+ nsecs_real = timekeeping_get_ns();
+
+ /* If arch requires, add in gettimeoffset() */
+ nsecs_real += arch_gettimeoffset();
+
+ } while (read_seqretry(&xtime_lock, seq));
+
+ timespec_add_ns(ts_raw, nsecs_raw);
+ timespec_add_ns(ts_real, nsecs_real);
+}
+EXPORT_SYMBOL(getnstime_raw_and_real);
+
+/**
* do_gettimeofday - Returns the time of day in a timeval
* @tv: pointer to the timeval to be set
*
--
1.6.6.1
This commit adds hardpps() implementation based upon the original one
from the NTPv4 reference kernel code from David Mills. However, it is
highly optimized towards very fast syncronization and maximum stickness
to PPS signal. The typical error is less then a microsecond.
To make it sync faster I had to throw away exponential phase filter so
that the full phase offset is corrected immediately. Then I also had to
throw away median phase filter because it gives a bigger error itself
if used without exponential filter.
Maybe we will find an appropriate filtering scheme in the future but
it's not necessary if the signal quality is ok.
Signed-off-by: Alexander Gordeev <[email protected]>
---
drivers/pps/Kconfig | 1 +
include/linux/timex.h | 1 +
kernel/time/Kconfig | 7 +
kernel/time/ntp.c | 420 +++++++++++++++++++++++++++++++++++++++++++++++--
4 files changed, 414 insertions(+), 15 deletions(-)
diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
index cc2eb8e..2bd4f65 100644
--- a/drivers/pps/Kconfig
+++ b/drivers/pps/Kconfig
@@ -7,6 +7,7 @@ menu "PPS support"
config PPS
tristate "PPS support"
depends on EXPERIMENTAL
+ select NTP_PPS
---help---
PPS (Pulse Per Second) is a special pulse provided by some GPS
antennae. Userland can use it to get a high-precision time
diff --git a/include/linux/timex.h b/include/linux/timex.h
index e6967d1..5a93cd3 100644
--- a/include/linux/timex.h
+++ b/include/linux/timex.h
@@ -274,6 +274,7 @@ extern u64 tick_length;
extern void second_overflow(void);
extern void update_ntp_one_tick(void);
extern int do_adjtimex(struct timex *);
+extern void hardpps(const struct timespec *, const struct timespec *);
/* Don't use! Compatibility define for existing users. */
#define tickadj (500/HZ ? : 1)
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 95ed429..2da4900 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -27,3 +27,10 @@ config GENERIC_CLOCKEVENTS_BUILD
default y
depends on GENERIC_CLOCKEVENTS || GENERIC_CLOCKEVENTS_MIGR
+config NTP_PPS
+ bool "PPS kernel consumer support"
+ depends on PPS
+ help
+ This option adds support for direct in-kernel time
+ syncronization using an external PPS signal.
+
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 4800f93..6db097a 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -14,6 +14,7 @@
#include <linux/timex.h>
#include <linux/time.h>
#include <linux/mm.h>
+#include <linux/module.h>
/*
* NTP timekeeping variables:
@@ -74,6 +75,161 @@ long time_adjust;
/* constant (boot-param configurable) NTP tick adjustment (upscaled) */
static s64 ntp_tick_adj;
+#ifdef CONFIG_NTP_PPS
+
+/*
+ * The following variables are used when a pulse-per-second (PPS) signal
+ * is available. They establish the engineering parameters of the clock
+ * discipline loop when controlled by the PPS signal.
+ */
+#define PPS_VALID 120 /* PPS signal watchdog max (s) */
+#define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
+#define PPS_INTMIN 2 /* min freq interval (s) (shift) */
+#define PPS_INTMAX 8 /* max freq interval (s) (shift) */
+#define PPS_INTCOUNT 4 /* number of consecutive good intervals to
+ increase pps_shift or consecutive bad
+ intervals to decrease it */
+#define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
+
+static int pps_valid; /* signal watchdog counter */
+static long pps_tf[3]; /* phase median filter */
+static long pps_jitter; /* current jitter (ns) */
+static struct timespec pps_fbase; /* beginning of the last freq interval */
+static int pps_shift; /* current interval duration (s) (shift) */
+static int pps_intcnt; /* interval counter */
+static s64 pps_freq; /* frequency offset (scaled ns/s) */
+static long pps_stabil; /* current stability (scaled ns/s) */
+
+/*
+ * PPS signal quality monitors
+ */
+static long pps_calcnt; /* calibration intervals */
+static long pps_jitcnt; /* jitter limit exceeded */
+static long pps_stbcnt; /* stability limit exceeded */
+static long pps_errcnt; /* calibration errors */
+
+
+/**
+ * pps_clear - Clears the PPS state variables
+ *
+ * Must be called while holding a write on the xtime_lock
+ */
+static inline void pps_clear(void)
+{
+ pps_shift = PPS_INTMIN;
+ pps_tf[0] = 0;
+ pps_tf[1] = 0;
+ pps_tf[2] = 0;
+ pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
+ pps_freq = 0;
+}
+
+/* PPS kernel consumer compensates the whole phase error immediately.
+ * Otherwise, reduce the offset by a fixed factor times the time constant.
+ */
+static inline s64 ntp_offset_chunk(s64 offset)
+{
+ if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
+ return offset;
+ else
+ return shift_right(offset, SHIFT_PLL + time_constant);
+}
+
+/* Decrease pps_valid to indicate that another second has passed since
+ * the last PPS signal. When it reaches 0, indicate that PPS signal is
+ * missing.
+ *
+ * Must be called while holding a write on the xtime_lock
+ */
+static inline void pps_dec_valid(void)
+{
+ if (pps_valid > 0)
+ pps_valid--;
+ else
+ time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
+ STA_PPSWANDER | STA_PPSERROR);
+}
+
+static inline void pps_reset_freq_interval(void)
+{
+ /* the PPS calibration interval may end
+ surprisingly early */
+ pps_shift = PPS_INTMIN;
+ pps_intcnt = 0;
+}
+
+static inline void pps_set_freq(s64 freq)
+{
+ pps_freq = freq;
+}
+
+static inline int is_error_status(int status)
+{
+ return (time_status & (STA_UNSYNC|STA_CLOCKERR))
+ /* PPS signal lost when either PPS time or
+ * PPS frequency synchronization requested
+ */
+ || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
+ && !(time_status & STA_PPSSIGNAL))
+ /* PPS jitter exceeded when
+ * PPS time synchronization requested */
+ || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
+ == (STA_PPSTIME|STA_PPSJITTER))
+ /* PPS wander exceeded or calibration error when
+ * PPS frequency synchronization requested
+ */
+ || ((time_status & STA_PPSFREQ)
+ && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
+}
+
+static inline void pps_fill_timex(struct timex *txc)
+{
+ txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
+ PPM_SCALE_INV, NTP_SCALE_SHIFT);
+ txc->jitter = pps_jitter;
+ if (!(time_status & STA_NANO))
+ txc->jitter /= NSEC_PER_USEC;
+ txc->shift = pps_shift;
+ txc->stabil = pps_stabil;
+ txc->jitcnt = pps_jitcnt;
+ txc->calcnt = pps_calcnt;
+ txc->errcnt = pps_errcnt;
+ txc->stbcnt = pps_stbcnt;
+}
+
+#else /* !CONFIG_NTP_PPS */
+
+static inline void pps_clear(void) {}
+
+static inline s64 ntp_offset_chunk(s64 offset)
+{
+ return shift_right(offset, SHIFT_PLL + time_constant);
+}
+
+static inline void pps_dec_valid(void) {}
+static inline void pps_reset_freq_interval(void) {}
+static inline void pps_set_freq(s64 freq) {}
+
+static inline int is_error_status(int status)
+{
+ return status & (STA_UNSYNC|STA_CLOCKERR);
+}
+
+static inline void pps_fill_timex(struct timex *txc)
+{
+ /* PPS is not implemented, so these are zero */
+ txc->ppsfreq = 0;
+ txc->jitter = 0;
+ txc->shift = 0;
+ txc->stabil = 0;
+ txc->jitcnt = 0;
+ txc->calcnt = 0;
+ txc->errcnt = 0;
+ txc->stbcnt = 0;
+}
+
+#endif /* CONFIG_NTP_PPS */
+
/*
* NTP methods:
*/
@@ -177,6 +333,9 @@ void ntp_clear(void)
tick_length = tick_length_base;
time_offset = 0;
+
+ /* Clear PPS state variables */
+ pps_clear();
}
/*
@@ -242,16 +401,16 @@ void second_overflow(void)
time_status |= STA_UNSYNC;
}
- /*
- * Compute the phase adjustment for the next second. The offset is
- * reduced by a fixed factor times the time constant.
- */
+ /* Compute the phase adjustment for the next second */
tick_length = tick_length_base;
- delta = shift_right(time_offset, SHIFT_PLL + time_constant);
+ delta = ntp_offset_chunk(time_offset);
time_offset -= delta;
tick_length += delta;
+ /* Check PPS signal */
+ pps_dec_valid();
+
if (!time_adjust)
return;
@@ -361,6 +520,8 @@ static inline void process_adj_status(struct timex *txc, struct timespec *ts)
if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
time_state = TIME_OK;
time_status = STA_UNSYNC;
+ /* restart PPS frequency calibration */
+ pps_reset_freq_interval();
}
/*
@@ -410,6 +571,8 @@ static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts
time_freq = txc->freq * PPM_SCALE;
time_freq = min(time_freq, MAXFREQ_SCALED);
time_freq = max(time_freq, -MAXFREQ_SCALED);
+ /* update pps_freq */
+ pps_set_freq(time_freq);
}
if (txc->modes & ADJ_MAXERROR)
@@ -500,7 +663,8 @@ int do_adjtimex(struct timex *txc)
}
result = time_state; /* mostly `TIME_OK' */
- if (time_status & (STA_UNSYNC|STA_CLOCKERR))
+ /* check for errors */
+ if (is_error_status(time_status))
result = TIME_ERROR;
txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
@@ -514,15 +678,8 @@ int do_adjtimex(struct timex *txc)
txc->tick = tick_usec;
txc->tai = time_tai;
- /* PPS is not implemented, so these are zero */
- txc->ppsfreq = 0;
- txc->jitter = 0;
- txc->shift = 0;
- txc->stabil = 0;
- txc->jitcnt = 0;
- txc->calcnt = 0;
- txc->errcnt = 0;
- txc->stbcnt = 0;
+ /* fill PPS status fields */
+ pps_fill_timex(txc);
write_sequnlock_irq(&xtime_lock);
@@ -536,6 +693,239 @@ int do_adjtimex(struct timex *txc)
return result;
}
+#ifdef CONFIG_NTP_PPS
+
+struct pps_normtime {
+ __kernel_time_t sec; /* seconds */
+ long nsec; /* nanoseconds */
+};
+
+/* normalize the timestamp so that nsec is in the
+ ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
+static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
+{
+ struct pps_normtime norm = {
+ .sec = ts.tv_sec,
+ .nsec = ts.tv_nsec
+ };
+
+ if (norm.nsec > (NSEC_PER_SEC >> 1)) {
+ norm.nsec -= NSEC_PER_SEC;
+ norm.sec++;
+ }
+
+ return norm;
+}
+
+/* get current phase correction and jitter */
+static inline long pps_phase_filter_get(long *jitter)
+{
+ *jitter = pps_tf[0] - pps_tf[1];
+ if (*jitter < 0)
+ *jitter = -*jitter;
+
+ /* TODO: test various filters */
+ return pps_tf[0];
+}
+
+/* add the sample to the phase filter */
+static inline void pps_phase_filter_add(long err)
+{
+ pps_tf[2] = pps_tf[1];
+ pps_tf[1] = pps_tf[0];
+ pps_tf[0] = err;
+}
+
+/* decrease frequency calibration interval length.
+ * It is halved after four consecutive unstable intervals.
+ */
+static inline void pps_dec_freq_interval(void)
+{
+ if (--pps_intcnt <= -PPS_INTCOUNT) {
+ pps_intcnt = -PPS_INTCOUNT;
+ if (pps_shift > PPS_INTMIN) {
+ pps_shift--;
+ pps_intcnt = 0;
+ }
+ }
+}
+
+/* increase frequency calibration interval length.
+ * It is doubled after four consecutive stable intervals.
+ */
+static inline void pps_inc_freq_interval(void)
+{
+ if (++pps_intcnt >= PPS_INTCOUNT) {
+ pps_intcnt = PPS_INTCOUNT;
+ if (pps_shift < PPS_INTMAX) {
+ pps_shift++;
+ pps_intcnt = 0;
+ }
+ }
+}
+
+/* update clock frequency based on MONOTONIC_RAW clock PPS signal
+ * timestamps
+ *
+ * At the end of the calibration interval the difference between the
+ * first and last MONOTONIC_RAW clock timestamps divided by the length
+ * of the interval becomes the frequency update. If the interval was
+ * too long, the data are discarded.
+ * Returns the difference between old and new frequency values.
+ */
+static long hardpps_update_freq(struct pps_normtime freq_norm)
+{
+ long delta, delta_mod;
+ s64 ftemp;
+
+ /* check if the frequency interval was too long */
+ if (freq_norm.sec > (2 << pps_shift)) {
+ time_status |= STA_PPSERROR;
+ pps_errcnt++;
+ pps_dec_freq_interval();
+ pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
+ freq_norm.sec);
+ return 0;
+ }
+
+ /* here the raw frequency offset and wander (stability) is
+ * calculated. If the wander is less than the wander threshold
+ * the interval is increased; otherwise it is decreased.
+ */
+ ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
+ freq_norm.sec);
+ delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
+ pps_freq = ftemp;
+ if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
+ pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
+ time_status |= STA_PPSWANDER;
+ pps_stbcnt++;
+ pps_dec_freq_interval();
+ } else { /* good sample */
+ pps_inc_freq_interval();
+ }
+
+ /* the stability metric is calculated as the average of recent
+ * frequency changes, but is used only for performance
+ * monitoring
+ */
+ delta_mod = delta;
+ if (delta_mod < 0)
+ delta_mod = -delta_mod;
+ pps_stabil += (div_s64(((s64)delta_mod) <<
+ (NTP_SCALE_SHIFT - SHIFT_USEC),
+ NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
+
+ /* if enabled, the system clock frequency is updated */
+ if ((time_status & STA_PPSFREQ) != 0 &&
+ (time_status & STA_FREQHOLD) == 0) {
+ time_freq = pps_freq;
+ ntp_update_frequency();
+ }
+
+ return delta;
+}
+
+/* correct REALTIME clock phase error against PPS signal */
+static void hardpps_update_phase(long error)
+{
+ long correction = -error;
+ long jitter;
+
+ /* add the sample to the median filter */
+ pps_phase_filter_add(correction);
+ correction = pps_phase_filter_get(&jitter);
+
+ /* Nominal jitter is due to PPS signal noise. If it exceeds the
+ * threshold, the sample is discarded; otherwise, if so enabled,
+ * the time offset is updated.
+ */
+ if (jitter > (pps_jitter << PPS_POPCORN)) {
+ pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
+ jitter, (pps_jitter << PPS_POPCORN));
+ time_status |= STA_PPSJITTER;
+ pps_jitcnt++;
+ } else if (time_status & STA_PPSTIME) {
+ /* correct the time using the phase offset */
+ time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
+ NTP_INTERVAL_FREQ);
+ /* cancel running adjtime() */
+ time_adjust = 0;
+ }
+ /* update jitter */
+ pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
+}
+
+/*
+ * hardpps() - discipline CPU clock oscillator to external PPS signal
+ *
+ * This routine is called at each PPS signal arrival in order to
+ * discipline the CPU clock oscillator to the PPS signal. It takes two
+ * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
+ * is used to correct clock phase error and the latter is used to
+ * correct the frequency.
+ *
+ * This code is based on David Mills's reference nanokernel
+ * implementation. It was mostly rewritten but keeps the same idea.
+ */
+void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
+{
+ struct pps_normtime pts_norm, freq_norm;
+ unsigned long flags;
+
+ pts_norm = pps_normalize_ts(*phase_ts);
+
+ write_seqlock_irqsave(&xtime_lock, flags);
+
+ /* clear the error bits, they will be set again if needed */
+ time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
+
+ /* indicate signal presence */
+ time_status |= STA_PPSSIGNAL;
+ pps_valid = PPS_VALID;
+
+ /* when called for the first time,
+ * just start the frequency interval */
+ if (unlikely(pps_fbase.tv_sec == 0)) {
+ pps_fbase = *raw_ts;
+ write_sequnlock_irq(&xtime_lock);
+ return;
+ }
+
+ /* ok, now we have a base for frequency calculation */
+ freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
+
+ /* check that the signal is in the range
+ * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
+ if ((freq_norm.sec == 0) ||
+ (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
+ (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
+ time_status |= STA_PPSJITTER;
+ /* restart the frequency calibration interval */
+ pps_fbase = *raw_ts;
+ write_sequnlock_irqrestore(&xtime_lock, flags);
+ pr_err("hardpps: PPSJITTER: bad pulse\n");
+ return;
+ }
+
+ /* signal is ok */
+
+ /* check if the current frequency interval is finished */
+ if (freq_norm.sec >= (1 << pps_shift)) {
+ pps_calcnt++;
+ /* restart the frequency calibration interval */
+ pps_fbase = *raw_ts;
+ hardpps_update_freq(freq_norm);
+ }
+
+ hardpps_update_phase(pts_norm.nsec);
+
+ write_sequnlock_irqrestore(&xtime_lock, flags);
+}
+EXPORT_SYMBOL(hardpps);
+
+#endif /* CONFIG_NTP_PPS */
+
static int __init ntp_tick_adj_setup(char *str)
{
ntp_tick_adj = simple_strtol(str, NULL, 0);
--
1.6.6.1
Add an optional feature of PPSAPI, kernel consumer support, which uses
the added hardpps() function.
Signed-off-by: Alexander Gordeev <[email protected]>
---
Documentation/ioctl/ioctl-number.txt | 2 +-
drivers/pps/kapi.c | 26 +++++++++++++
drivers/pps/pps.c | 67 +++++++++++++++++++++++++++++++++-
include/linux/pps.h | 7 ++++
include/linux/pps_kernel.h | 6 +++
5 files changed, 106 insertions(+), 2 deletions(-)
diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index 9473749..d68718b 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -152,7 +152,7 @@ Code Seq# Include File Comments
'p' 40-7F linux/nvram.h
'p' 80-9F user-space parport
<mailto:[email protected]>
-'p' a1-a4 linux/pps.h LinuxPPS
+'p' a1-a5 linux/pps.h LinuxPPS
<mailto:[email protected]>
'q' 00-1F linux/serio.h
'q' 80-FF Internet PhoneJACK, Internet LineJACK
diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
index b87f699..5871744 100644
--- a/drivers/pps/kapi.c
+++ b/drivers/pps/kapi.c
@@ -25,6 +25,7 @@
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/time.h>
+#include <linux/timex.h>
#include <linux/spinlock.h>
#include <linux/idr.h>
#include <linux/fs.h>
@@ -37,6 +38,12 @@
DEFINE_SPINLOCK(pps_idr_lock);
DEFINE_IDR(pps_idr);
+/* state variables to bind kernel consumer */
+/* PPS API (RFC 2783): current source and mode for ``kernel consumer'' */
+DEFINE_SPINLOCK(pps_kc_hardpps_lock);
+void *pps_kc_hardpps_dev; /* some unique pointer to device */
+int pps_kc_hardpps_mode; /* mode bits for kernel consumer */
+
/*
* Local functions
*/
@@ -248,6 +255,15 @@ void pps_unregister_source(int source)
}
spin_unlock_irq(&pps_idr_lock);
+ spin_lock_irq(&pps_kc_hardpps_lock);
+ if (pps == pps_kc_hardpps_dev) {
+ pps_kc_hardpps_mode = 0;
+ pps_kc_hardpps_dev = NULL;
+ spin_unlock_irq(&pps_kc_hardpps_lock);
+ pr_info("unbound kernel consumer on device removal\n");
+ } else
+ spin_unlock_irq(&pps_kc_hardpps_lock);
+
pps_unregister_cdev(pps);
pps_put_source(pps);
}
@@ -325,6 +341,16 @@ void pps_event(int source, struct pps_event_time *ts, int event, void *data)
captured = ~0;
}
+ spin_lock(&pps_kc_hardpps_lock);
+ if (pps == pps_kc_hardpps_dev && event & pps_kc_hardpps_mode) {
+ struct timespec p_ts = {
+ .tv_sec = ts->ts_real.sec,
+ .tv_nsec = ts->ts_real.nsec
+ };
+
+ hardpps(&p_ts, &ts->ts_raw);
+ }
+ spin_unlock(&pps_kc_hardpps_lock);
/* Wake up iif captured somthing */
if (captured) {
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index ca5183b..22fdcfe 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -62,6 +62,8 @@ static long pps_cdev_ioctl(struct file *file,
struct pps_device *pps = file->private_data;
struct pps_kparams params;
struct pps_fdata fdata;
+ struct pps_bind_args bind_args;
+ unsigned long irq_flags;
unsigned long ticks;
void __user *uarg = (void __user *) arg;
int __user *iuarg = (int __user *) arg;
@@ -186,9 +188,72 @@ static long pps_cdev_ioctl(struct file *file,
break;
+ case PPS_KC_BIND:
+ pr_info("PPS_KC_BIND: source %d\n", pps->id);
+
+ /* Check the capabilities */
+ if (!capable(CAP_SYS_TIME))
+ return -EPERM;
+
+ if (copy_from_user(&bind_args, uarg,
+ sizeof(struct pps_bind_args)))
+ return -EFAULT;
+
+ /* Check for supported capabilities */
+ if ((bind_args.edge & ~pps->info.mode) != 0) {
+ pr_err("PPS_KC_BIND: "
+ "unsupported capabilities (%x)\n",
+ bind_args.edge);
+ return -EINVAL;
+ }
+
+ /* Validate parameters roughly */
+ if (bind_args.tsformat != PPS_TSFMT_TSPEC ||
+ (bind_args.edge & ~PPS_CAPTUREBOTH) != 0 ||
+ bind_args.consumer != PPS_KC_HARDPPS) {
+ pr_err("PPS_KC_BIND: "
+ "invalid kcbind parameters (%x)\n",
+ bind_args.edge);
+ return -EINVAL;
+ }
+
+ /* Check if another consumer is already bound */
+ spin_lock_irqsave(&pps_kc_hardpps_lock, irq_flags);
+
+ if (bind_args.edge == 0)
+ if (pps_kc_hardpps_dev == pps) {
+ pps_kc_hardpps_mode = 0;
+ pps_kc_hardpps_dev = NULL;
+ spin_unlock_irqrestore(&pps_kc_hardpps_lock,
+ irq_flags);
+ pr_info("unbound kernel consumer\n");
+ } else {
+ spin_unlock_irqrestore(&pps_kc_hardpps_lock,
+ irq_flags);
+ pr_err("selected kernel consumer"
+ " is not bound\n");
+ return -EINVAL;
+ }
+ else
+ if (pps_kc_hardpps_dev == NULL ||
+ pps_kc_hardpps_dev == pps) {
+ pps_kc_hardpps_mode = bind_args.edge;
+ pps_kc_hardpps_dev = pps;
+ spin_unlock_irqrestore(&pps_kc_hardpps_lock,
+ irq_flags);
+ pr_info("bound kernel consumer: dev=%p, "
+ "edge=0x%x\n", pps, bind_args.edge);
+ } else {
+ spin_unlock_irqrestore(&pps_kc_hardpps_lock,
+ irq_flags);
+ pr_err("another kernel consumer"
+ " is already bound\n");
+ return -EINVAL;
+ }
+ break;
+
default:
return -ENOTTY;
- break;
}
return 0;
diff --git a/include/linux/pps.h b/include/linux/pps.h
index 0194ab0..a9bb1d9 100644
--- a/include/linux/pps.h
+++ b/include/linux/pps.h
@@ -114,11 +114,18 @@ struct pps_fdata {
struct pps_ktime timeout;
};
+struct pps_bind_args {
+ int tsformat; /* format of time stamps */
+ int edge; /* selected event type */
+ int consumer; /* selected kernel consumer */
+};
+
#include <linux/ioctl.h>
#define PPS_GETPARAMS _IOR('p', 0xa1, struct pps_kparams *)
#define PPS_SETPARAMS _IOW('p', 0xa2, struct pps_kparams *)
#define PPS_GETCAP _IOR('p', 0xa3, int *)
#define PPS_FETCH _IOWR('p', 0xa4, struct pps_fdata *)
+#define PPS_KC_BIND _IOW('p', 0xa5, struct pps_bind_args *)
#endif /* _PPS_H_ */
diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
index 9bda892..2b203cd 100644
--- a/include/linux/pps_kernel.h
+++ b/include/linux/pps_kernel.h
@@ -80,6 +80,12 @@ extern struct timespec pps_irq_ts[];
extern struct device_attribute pps_attrs[];
+/* state variables to bind kernel consumer */
+/* PPS API (RFC 2783): current source and mode for ``kernel consumer'' */
+extern spinlock_t pps_kc_hardpps_lock;
+extern void *pps_kc_hardpps_dev; /* some unique pointer to device */
+extern int pps_kc_hardpps_mode; /* mode bits for kernel consumer */
+
/*
* Exported functions
*/
--
1.6.6.1
Add a helper function to gather timestamps. This way clients don't have
to duplicate it.
Signed-off-by: Alexander Gordeev <[email protected]>
---
drivers/pps/kapi.c | 15 +++++++++------
include/linux/pps_kernel.h | 23 ++++++++++++++++++++++-
2 files changed, 31 insertions(+), 7 deletions(-)
diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
index 2d414e2..b87f699 100644
--- a/drivers/pps/kapi.c
+++ b/drivers/pps/kapi.c
@@ -267,7 +267,7 @@ EXPORT_SYMBOL(pps_unregister_source);
* pps->info.echo(source, event, data);
*/
-void pps_event(int source, struct pps_ktime *ts, int event, void *data)
+void pps_event(int source, struct pps_event_time *ts, int event, void *data)
{
struct pps_device *pps;
unsigned long flags;
@@ -284,7 +284,8 @@ void pps_event(int source, struct pps_ktime *ts, int event, void *data)
return;
pr_debug("PPS event on source %d at %llu.%06u\n",
- pps->id, (unsigned long long) ts->sec, ts->nsec);
+ pps->id, (unsigned long long) ts->ts_real.sec,
+ ts->ts_real.nsec);
spin_lock_irqsave(&pps->lock, flags);
@@ -298,10 +299,11 @@ void pps_event(int source, struct pps_ktime *ts, int event, void *data)
(pps->params.mode & PPS_CAPTUREASSERT)) {
/* We have to add an offset? */
if (pps->params.mode & PPS_OFFSETASSERT)
- pps_add_offset(ts, &pps->params.assert_off_tu);
+ pps_add_offset(&ts->ts_real,
+ &pps->params.assert_off_tu);
/* Save the time stamp */
- pps->assert_tu = *ts;
+ pps->assert_tu = ts->ts_real;
pps->assert_sequence++;
pr_debug("capture assert seq #%u for source %d\n",
pps->assert_sequence, source);
@@ -312,10 +314,11 @@ void pps_event(int source, struct pps_ktime *ts, int event, void *data)
(pps->params.mode & PPS_CAPTURECLEAR)) {
/* We have to add an offset? */
if (pps->params.mode & PPS_OFFSETCLEAR)
- pps_add_offset(ts, &pps->params.clear_off_tu);
+ pps_add_offset(&ts->ts_real,
+ &pps->params.clear_off_tu);
/* Save the time stamp */
- pps->clear_tu = *ts;
+ pps->clear_tu = ts->ts_real;
pps->clear_sequence++;
pr_debug("capture clear seq #%u for source %d\n",
pps->clear_sequence, source);
diff --git a/include/linux/pps_kernel.h b/include/linux/pps_kernel.h
index e0a193f..a2804c1 100644
--- a/include/linux/pps_kernel.h
+++ b/include/linux/pps_kernel.h
@@ -40,6 +40,10 @@ struct pps_source_info {
struct device *dev;
};
+struct pps_event_time {
+ struct pps_ktime ts_real;
+};
+
/* The main struct */
struct pps_device {
struct pps_source_info info; /* PSS source info */
@@ -86,4 +90,21 @@ extern int pps_register_source(struct pps_source_info *info,
extern void pps_unregister_source(int source);
extern int pps_register_cdev(struct pps_device *pps);
extern void pps_unregister_cdev(struct pps_device *pps);
-extern void pps_event(int source, struct pps_ktime *ts, int event, void *data);
+extern void pps_event(int source, struct pps_event_time *ts, int event,
+ void *data);
+
+static inline void timespec_to_pps_ktime(struct pps_ktime *kt,
+ struct timespec ts)
+{
+ kt->sec = ts.tv_sec;
+ kt->nsec = ts.tv_nsec;
+}
+
+static inline void pps_get_ts(struct pps_event_time *ts)
+{
+ struct timespec ts_real;
+
+ getnstimeofday(&ts_real);
+ timespec_to_pps_ktime(&ts->ts_real, ts_real);
+}
+
--
1.6.6.1
Add parallel port PPS client. It uses a standard method for capturing
timestamps for assert edge transitions: getting a timestamp soon after
an interrupt has happened. This is not a very precise source of time
information due to interrupt handling delays. However, timestamps for
clear edge transitions are much more precise because the interrupt
handler continuously polls hardware port until the transition is done.
Hardware port operations require only about 1us so the maximum error
should not exceed this value. This was my primary goal when developing
this client.
Signed-off-by: Alexander Gordeev <[email protected]>
---
drivers/pps/Kconfig | 2 +
drivers/pps/Makefile | 2 +-
drivers/pps/clients/Kconfig | 16 +++
drivers/pps/clients/Makefile | 9 ++
drivers/pps/clients/pps_parport.c | 211 +++++++++++++++++++++++++++++++++++++
5 files changed, 239 insertions(+), 1 deletions(-)
create mode 100644 drivers/pps/clients/Kconfig
create mode 100644 drivers/pps/clients/Makefile
create mode 100644 drivers/pps/clients/pps_parport.c
diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
index f3b14cd..3b70d9e 100644
--- a/drivers/pps/Kconfig
+++ b/drivers/pps/Kconfig
@@ -31,6 +31,8 @@ config PPS_DEBUG
messages to the system log. Select this if you are having a
problem with PPS support and want to see more of what is going on.
+source drivers/pps/clients/Kconfig
+
source drivers/pps/generators/Kconfig
endmenu
diff --git a/drivers/pps/Makefile b/drivers/pps/Makefile
index b299814..1906eb7 100644
--- a/drivers/pps/Makefile
+++ b/drivers/pps/Makefile
@@ -4,6 +4,6 @@
pps_core-y := pps.o kapi.o sysfs.o
obj-$(CONFIG_PPS) := pps_core.o
-obj-y += generators/
+obj-y += clients/ generators/
ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
diff --git a/drivers/pps/clients/Kconfig b/drivers/pps/clients/Kconfig
new file mode 100644
index 0000000..969a486
--- /dev/null
+++ b/drivers/pps/clients/Kconfig
@@ -0,0 +1,16 @@
+#
+# PPS clients configuration
+#
+
+if PPS
+
+comment "PPS clients support"
+
+config PPS_CLIENT_PARPORT
+ tristate "Parallel port PPS client"
+ depends on PPS && PARPORT
+ help
+ If you say yes here you get support for a PPS source connected
+ with the interrupt pin of your parallel port.
+
+endif
diff --git a/drivers/pps/clients/Makefile b/drivers/pps/clients/Makefile
new file mode 100644
index 0000000..95f6fc3
--- /dev/null
+++ b/drivers/pps/clients/Makefile
@@ -0,0 +1,9 @@
+#
+# Makefile for PPS clients.
+#
+
+obj-$(CONFIG_PPS_CLIENT_PARPORT) += pps_parport.o
+
+ifeq ($(CONFIG_PPS_DEBUG),y)
+EXTRA_CFLAGS += -DDEBUG
+endif
diff --git a/drivers/pps/clients/pps_parport.c b/drivers/pps/clients/pps_parport.c
new file mode 100644
index 0000000..390f8e4
--- /dev/null
+++ b/drivers/pps/clients/pps_parport.c
@@ -0,0 +1,211 @@
+/*
+ * pps_parport.c -- kernel parallel port PPS client
+ *
+ *
+ * Copyright (C) 2009 Alexander Gordeev <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+/*
+ * TODO:
+ * 1. try using SA_NODELAY for parport irq handler
+ * 2. test under heavy load
+ * 3. implement echo over SEL pin
+ * 4. module parameters
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/irqnr.h>
+#include <linux/time.h>
+#include <linux/parport.h>
+#include <linux/pps_kernel.h>
+
+#define DRVNAME "pps_parport"
+#define DRVDESC "parallel port PPS client"
+
+/* maximum number of port reads when polling for signal clear */
+#define RECEIVE_TIMEOUT 100
+
+/* internal per port structure */
+struct pps_client_pp {
+ struct pardevice *pardev; /* parport device */
+ int source; /* PPS source number */
+};
+
+#define SIGNAL_IS_SET(port) \
+ ((port->ops->read_status(port) & PARPORT_STATUS_ACK) != 0)
+
+/* parport interrupt handler */
+static void parport_irq(void *handle)
+{
+ struct pps_event_time ts_assert, ts_clear;
+ struct pps_client_pp *dev = handle;
+ struct parport *port = dev->pardev->port;
+ int i;
+ unsigned long flags;
+
+ /* first of all we get the time stamp... */
+ pps_get_ts(&ts_assert);
+
+ /* check the signal (no signal means the pulse is lost this time) */
+ if (!SIGNAL_IS_SET(port)) {
+ pr_err(DRVNAME ": lost the signal\n");
+ return;
+ }
+
+ /* FIXME: this is here until we have a fast interrupt */
+ local_irq_save(flags);
+ /* poll the port until the signal is unset */
+ for (i = RECEIVE_TIMEOUT; i; i--)
+ if (!SIGNAL_IS_SET(port)) {
+ pps_get_ts(&ts_clear);
+ local_irq_restore(flags);
+
+ /* FIXME: move these two calls to workqueue? */
+ /* fire assert event */
+ pps_event(dev->source, &ts_assert,
+ PPS_CAPTUREASSERT, NULL);
+ /* fire clear event */
+ pps_event(dev->source, &ts_clear,
+ PPS_CAPTURECLEAR, NULL);
+
+ return;
+ }
+ local_irq_restore(flags);
+
+ /* timeout */
+ pr_err(DRVNAME ": timeout in interrupt handler while waiting"
+ " for signal clear\n");
+}
+
+/* the PPS echo function */
+static void pps_echo(int source, int event, void *data)
+{
+ pr_info("echo %s %s for source %d\n",
+ event & PPS_CAPTUREASSERT ? "assert" : "",
+ event & PPS_CAPTURECLEAR ? "clear" : "",
+ source);
+}
+
+static void parport_attach(struct parport *port)
+{
+ struct pps_client_pp *device;
+ struct pps_source_info info = {
+ .name = DRVNAME,
+ .path = "",
+ .mode = PPS_CAPTUREBOTH | \
+ PPS_OFFSETASSERT | PPS_OFFSETCLEAR | \
+ PPS_ECHOASSERT | PPS_ECHOCLEAR | \
+ PPS_CANWAIT | PPS_TSFMT_TSPEC,
+ .echo = pps_echo,
+ .owner = THIS_MODULE,
+ };
+
+ device = kzalloc(sizeof(struct pps_client_pp), GFP_KERNEL);
+ if (!device) {
+ pr_err(DRVNAME ": memory allocation failed, not attaching\n");
+ return;
+ }
+
+ device->pardev = parport_register_device(port, DRVNAME,
+ NULL, NULL, parport_irq, 0, device);
+ if (!device->pardev) {
+ pr_err(DRVNAME ": couldn't register with %s\n", port->name);
+ goto err_free;
+ }
+
+ if (parport_claim_or_block(device->pardev) < 0) {
+ pr_err(DRVNAME ": couldn't claim %s\n", port->name);
+ goto err_unregister_dev;
+ }
+
+ device->source = pps_register_source(&info,
+ PPS_CAPTUREBOTH | PPS_OFFSETASSERT | PPS_OFFSETCLEAR);
+ if (device->source < 0) {
+ pr_err(DRVNAME ": couldn't register PPS source\n");
+ goto err_release_dev;
+ }
+
+ port->ops->enable_irq(port);
+
+ pr_info(DRVNAME ": attached to %s\n", port->name);
+
+ return;
+
+err_release_dev:
+ parport_release(device->pardev);
+err_unregister_dev:
+ parport_unregister_device(device->pardev);
+err_free:
+ kfree(device);
+}
+
+static void parport_detach(struct parport *port)
+{
+ struct pardevice *pardev = port->cad;
+ struct pps_client_pp *device;
+
+ /* oooh, this is ugly! */
+ if (strcmp(pardev->name, DRVNAME))
+ /* not our port */
+ return;
+
+ device = pardev->private;
+
+ port->ops->disable_irq(port);
+ pps_unregister_source(device->source);
+ parport_release(pardev);
+ parport_unregister_device(pardev);
+ kfree(device);
+}
+
+static struct parport_driver pps_parport_driver = {
+ .name = DRVNAME,
+ .attach = parport_attach,
+ .detach = parport_detach,
+};
+
+/* module staff */
+
+static int __init pps_parport_init(void)
+{
+ int ret;
+
+ pr_info(DRVNAME ": " DRVDESC "\n");
+
+ ret = parport_register_driver(&pps_parport_driver);
+ if (ret) {
+ pr_err(DRVNAME ": unable to register with parport\n");
+ return ret;
+ }
+
+ return 0;
+}
+
+static void __exit pps_parport_exit(void)
+{
+ parport_unregister_driver(&pps_parport_driver);
+}
+
+module_init(pps_parport_init);
+module_exit(pps_parport_exit);
+
+MODULE_AUTHOR("Alexander Gordeev <[email protected]>");
+MODULE_DESCRIPTION(DRVDESC);
+MODULE_LICENSE("GPL");
--
1.6.6.1
Add PPS signal generator which utilizes STROBE pin of a parallel port to
send PPS signals. It uses parport abstraction layer and hrtimers to
precisely control the signal.
Signed-off-by: Alexander Gordeev <[email protected]>
---
drivers/pps/Kconfig | 2 +
drivers/pps/Makefile | 1 +
drivers/pps/generators/Kconfig | 17 ++
drivers/pps/generators/Makefile | 9 +
drivers/pps/generators/pps_gen_parport.c | 264 ++++++++++++++++++++++++++++++
5 files changed, 293 insertions(+), 0 deletions(-)
create mode 100644 drivers/pps/generators/Kconfig
create mode 100644 drivers/pps/generators/Makefile
create mode 100644 drivers/pps/generators/pps_gen_parport.c
diff --git a/drivers/pps/Kconfig b/drivers/pps/Kconfig
index 2bd4f65..f3b14cd 100644
--- a/drivers/pps/Kconfig
+++ b/drivers/pps/Kconfig
@@ -31,4 +31,6 @@ config PPS_DEBUG
messages to the system log. Select this if you are having a
problem with PPS support and want to see more of what is going on.
+source drivers/pps/generators/Kconfig
+
endmenu
diff --git a/drivers/pps/Makefile b/drivers/pps/Makefile
index 19ea582..b299814 100644
--- a/drivers/pps/Makefile
+++ b/drivers/pps/Makefile
@@ -4,5 +4,6 @@
pps_core-y := pps.o kapi.o sysfs.o
obj-$(CONFIG_PPS) := pps_core.o
+obj-y += generators/
ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
diff --git a/drivers/pps/generators/Kconfig b/drivers/pps/generators/Kconfig
new file mode 100644
index 0000000..9cc1118
--- /dev/null
+++ b/drivers/pps/generators/Kconfig
@@ -0,0 +1,17 @@
+#
+# PPS clients configuration
+#
+
+if PPS
+
+comment "PPS generators support"
+
+config PPS_GENERATOR_PARPORT
+ tristate "Parallel port PPS signal generator"
+ depends on PARPORT != n && GENERIC_TIME
+ help
+ If you say yes here you get support for a PPS signal generator which
+ utilizes STROBE pin of a parallel port to send PPS signals. It uses
+ parport abstraction layer and hrtimers to precisely control the signal.
+
+endif
diff --git a/drivers/pps/generators/Makefile b/drivers/pps/generators/Makefile
new file mode 100644
index 0000000..303304a
--- /dev/null
+++ b/drivers/pps/generators/Makefile
@@ -0,0 +1,9 @@
+#
+# Makefile for PPS generators.
+#
+
+obj-$(CONFIG_PPS_GENERATOR_PARPORT) += pps_gen_parport.o
+
+ifeq ($(CONFIG_PPS_DEBUG),y)
+EXTRA_CFLAGS += -DDEBUG
+endif
diff --git a/drivers/pps/generators/pps_gen_parport.c b/drivers/pps/generators/pps_gen_parport.c
new file mode 100644
index 0000000..e7cce30
--- /dev/null
+++ b/drivers/pps/generators/pps_gen_parport.c
@@ -0,0 +1,264 @@
+/*
+ * pps_gen_parport.c -- kernel parallel port PPS signal generator
+ *
+ *
+ * Copyright (C) 2009 Alexander Gordeev <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+/*
+ * TODO:
+ * 1. module parameters
+ * 2. check that local interrupts are blocked in hrtimer handler
+ * 3. fix issues when realtime clock is adjusted in a leap
+ * 4. test under heavy load
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/time.h>
+#include <linux/hrtimer.h>
+#include <linux/parport.h>
+
+#define DRVNAME "pps_gen_parport"
+#define DRVDESC "parallel port PPS signal generator"
+
+#define SIGNAL 0
+#define NO_SIGNAL PARPORT_CONTROL_STROBE
+
+#define SEND_DELAY 30000 /* delay between setting and
+ dropping the signal (ns) */
+#define SAFETY_INTERVAL 3000 /* set the hrtimer earlier for safety (ns) */
+
+/* internal per port structure */
+struct pps_generator_pp {
+ struct pardevice *pardev; /* parport device */
+ struct hrtimer timer;
+ long port_write_time; /* calibrated port write time (ns) */
+};
+
+static struct pps_generator_pp device = {
+ .pardev = NULL,
+};
+
+static int attached;
+
+/* calibrated time between a hrtimer event and the reaction */
+static long hrtimer_error = SAFETY_INTERVAL;
+
+/* the kernel hrtimer event */
+static enum hrtimer_restart hrtimer_event(struct hrtimer *timer)
+{
+ struct timespec expire_time, ts1, ts2, ts3, dts;
+ struct pps_generator_pp *dev;
+ struct parport *port;
+ long lim, delta;
+ unsigned long flags;
+
+ /* NB: approx time with blocked interrupts =
+ SEND_DELAY + 3 * SAFETY_INTERVAL */
+ local_irq_save(flags);
+
+ /* first of all we get the time stamp... */
+ getnstimeofday(&ts1);
+ expire_time = ktime_to_timespec(timer->_expires);
+ dev = container_of(timer, struct pps_generator_pp, timer);
+ lim = NSEC_PER_SEC - SEND_DELAY - dev->port_write_time;
+
+ /* check if we are late */
+ if (expire_time.tv_sec != ts1.tv_sec || ts1.tv_nsec > lim) {
+ local_irq_restore(flags);
+ pr_err(DRVNAME ": we are late this time %ld.%09ld\n",
+ ts1.tv_sec, ts1.tv_nsec);
+ goto done;
+ }
+
+ /* busy loop until the time is right for an assert edge */
+ do {
+ getnstimeofday(&ts2);
+ } while (expire_time.tv_sec == ts2.tv_sec && ts2.tv_nsec < lim);
+
+ /* set the signal */
+ port = dev->pardev->port;
+ port->ops->write_control(port, SIGNAL);
+
+ /* busy loop until the time is right for a clear edge */
+ lim = NSEC_PER_SEC - dev->port_write_time;
+ do {
+ getnstimeofday(&ts2);
+ } while (expire_time.tv_sec == ts2.tv_sec && ts2.tv_nsec < lim);
+
+ /* unset the signal */
+ port->ops->write_control(port, NO_SIGNAL);
+
+ getnstimeofday(&ts3);
+
+ local_irq_restore(flags);
+
+ /* update calibrated port write time */
+ dts = timespec_sub(ts3, ts2);
+ dev->port_write_time =
+ (dev->port_write_time + timespec_to_ns(&dts)) >> 1;
+
+done:
+ /* update calibrated hrtimer error */
+ dts = timespec_sub(ts1, expire_time);
+ delta = timespec_to_ns(&dts);
+ /* If the new error value is bigger then the old, use the new
+ * value, if not then slowly move towards the new value. This
+ * way it should be safe in bad conditions and efficient in
+ * good conditions.
+ */
+ if (delta >= hrtimer_error)
+ hrtimer_error = delta;
+ else
+ hrtimer_error = (3 * hrtimer_error + delta) >> 2;
+
+ /* update the hrtimer expire time */
+ hrtimer_set_expires(timer,
+ ktime_set(expire_time.tv_sec + 1,
+ NSEC_PER_SEC - (SEND_DELAY +
+ dev->port_write_time + SAFETY_INTERVAL +
+ 2 * hrtimer_error)));
+
+ return HRTIMER_RESTART;
+}
+
+/* calibrate port write time */
+#define PORT_NTESTS_SHIFT 5
+static void calibrate_port(struct pps_generator_pp *dev)
+{
+ struct parport *port = dev->pardev->port;
+ int i;
+ long acc = 0;
+
+ for (i = 0; i < (1 << PORT_NTESTS_SHIFT); i++) {
+ struct timespec a, b;
+ unsigned long irq_flags;
+
+ local_irq_save(irq_flags);
+ getnstimeofday(&a);
+ port->ops->write_control(port, NO_SIGNAL);
+ getnstimeofday(&b);
+ local_irq_restore(irq_flags);
+
+ b = timespec_sub(b, a);
+ acc += timespec_to_ns(&b);
+ }
+
+ dev->port_write_time = acc >> PORT_NTESTS_SHIFT;
+ pr_info(DRVNAME ": port write takes %ldns\n", dev->port_write_time);
+}
+
+static inline ktime_t next_intr_time(struct pps_generator_pp *dev)
+{
+ struct timespec ts;
+
+ getnstimeofday(&ts);
+
+ return ktime_set(ts.tv_sec +
+ ((ts.tv_nsec > 990 * NSEC_PER_MSEC) ? 1 : 0),
+ NSEC_PER_SEC - (SEND_DELAY +
+ dev->port_write_time + 3 * SAFETY_INTERVAL));
+}
+
+static void parport_attach(struct parport *port)
+{
+ if (attached) {
+ /* we already have a port */
+ return;
+ }
+
+ device.pardev = parport_register_device(port, DRVNAME,
+ NULL, NULL, NULL, 0, &device);
+ if (!device.pardev) {
+ pr_err(DRVNAME ": couldn't register with %s\n", port->name);
+ return;
+ }
+
+ if (parport_claim_or_block(device.pardev) < 0) {
+ pr_err(DRVNAME ": couldn't claim %s\n", port->name);
+ goto err_unregister_dev;
+ }
+
+ pr_info(DRVNAME ": attached to %s\n", port->name);
+ attached = 1;
+
+ calibrate_port(&device);
+
+ hrtimer_init(&device.timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
+ device.timer.function = hrtimer_event;
+#ifdef CONFIG_PREEMPT_RT
+ /* hrtimer interrupt will run in the interrupt context with this */
+ device.timer.irqsafe = 1;
+#endif
+
+ hrtimer_start(&device.timer, next_intr_time(&device), HRTIMER_MODE_ABS);
+
+ return;
+
+err_unregister_dev:
+ parport_unregister_device(device.pardev);
+}
+
+static void parport_detach(struct parport *port)
+{
+ if (port->cad != device.pardev)
+ /* not our port */
+ return;
+
+ hrtimer_cancel(&device.timer);
+ parport_release(device.pardev);
+ parport_unregister_device(device.pardev);
+}
+
+static struct parport_driver pps_gen_parport_driver = {
+ .name = DRVNAME,
+ .attach = parport_attach,
+ .detach = parport_detach,
+};
+
+/* module staff */
+
+static int __init pps_gen_parport_init(void)
+{
+ int ret;
+
+ pr_info(DRVNAME ": " DRVDESC "\n");
+
+ ret = parport_register_driver(&pps_gen_parport_driver);
+ if (ret) {
+ pr_err(DRVNAME ": unable to register with parport\n");
+ return ret;
+ }
+
+ return 0;
+}
+
+static void __exit pps_gen_parport_exit(void)
+{
+ parport_unregister_driver(&pps_gen_parport_driver);
+ pr_info(DRVNAME ": hrtimer avg error is %ldns\n", hrtimer_error);
+}
+
+module_init(pps_gen_parport_init);
+module_exit(pps_gen_parport_exit);
+
+MODULE_AUTHOR("Alexander Gordeev <[email protected]>");
+MODULE_DESCRIPTION(DRVDESC);
+MODULE_LICENSE("GPL");
--
1.6.6.1