redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

pps: parport: use timespec64 instead of timespec 

getnstimeofday() is deprecated, so I'm converting this to use
ktime_get_real_ts64() as a safe replacement.  I considered using
ktime_get_real() instead, but since the algorithm here depends on the
exact timing, I decided to introduce fewer changes and leave the code
that determines the nanoseconds since the last seconds wrap untouched.

It's not entirely clear to me whether we should also change the time
base to CLOCK_BOOTTIME or CLOCK_TAI.  With boottime, we would be
independent of changes due to settimeofday() and only see the speed
adjustment from the upstream clock source, with the downside of having
the signal be at an arbirary offset from the start of the UTC second
signal.  With CLOCK_TAI, we would use the same offset from the UTC
second as before and still suffer from settimeofday() adjustments, but
would be less confused during leap seconds.

Both boottime and tai only offer usable (i.e.  avoiding ktime_t to
timespec64 conversion) interfaces for ktime_t though, so either way,
changing it wouldn't take significantly more work.  CLOCK_MONOTONIC
could be used with ktime_get_ts64(), but would lose synchronization
across a suspend/resume cycle, which seems worse.

Link: http://lkml.kernel.org/r/20180116171451.3095620-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hifive-unleashed-5.1
Arnd Bergmann 2018-02-06 15:40:21 -08:00 committed by Linus Torvalds
parent 2ee0826085
commit 28f3a488ed
1 changed files with 20 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
drivers/pps/generators/pps_gen_parport.c
View File

@ -70,7 +70,7 @@ 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 timespec64 expire_time, ts1, ts2, ts3, dts;
struct pps_generator_pp *dev;
struct parport *port;
long lim, delta;
@ -78,7 +78,7 @@ static enum hrtimer_restart hrtimer_event(struct hrtimer *timer)
/* We have to disable interrupts here. The idea is to prevent
* other interrupts on the same processor to introduce random
* lags while polling the clock. getnstimeofday() takes <1us on
* lags while polling the clock. ktime_get_real_ts64() takes <1us on
* most machines while other interrupt handlers can take much
* more potentially.
*
@ -88,22 +88,22 @@ static enum hrtimer_restart hrtimer_event(struct hrtimer *timer)
local_irq_save(flags);
/* first of all we get the time stamp... */
getnstimeofday(&ts1);
expire_time = ktime_to_timespec(hrtimer_get_softexpires(timer));
ktime_get_real_ts64(&ts1);
expire_time = ktime_to_timespec64(hrtimer_get_softexpires(timer));
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("we are late this time %ld.%09ld\n",
ts1.tv_sec, ts1.tv_nsec);
pr_err("we are late this time %lld.%09ld\n",
(s64)ts1.tv_sec, ts1.tv_nsec);
goto done;
}
/* busy loop until the time is right for an assert edge */
do {
getnstimeofday(&ts2);
ktime_get_real_ts64(&ts2);
} while (expire_time.tv_sec == ts2.tv_sec && ts2.tv_nsec < lim);
/* set the signal */
@ -113,25 +113,25 @@ static enum hrtimer_restart hrtimer_event(struct hrtimer *timer)
/* busy loop until the time is right for a clear edge */
lim = NSEC_PER_SEC - dev->port_write_time;
do {
getnstimeofday(&ts2);
ktime_get_real_ts64(&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);
ktime_get_real_ts64(&ts3);
local_irq_restore(flags);
/* update calibrated port write time */
dts = timespec_sub(ts3, ts2);
dts = timespec64_sub(ts3, ts2);
dev->port_write_time =
(dev->port_write_time + timespec_to_ns(&dts)) >> 1;
(dev->port_write_time + timespec64_to_ns(&dts)) >> 1;
done:
/* update calibrated hrtimer error */
dts = timespec_sub(ts1, expire_time);
delta = timespec_to_ns(&dts);
dts = timespec64_sub(ts1, expire_time);
delta = timespec64_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
@ -161,17 +161,17 @@ static void calibrate_port(struct pps_generator_pp *dev)
long acc = 0;
for (i = 0; i < (1 << PORT_NTESTS_SHIFT); i++) {
struct timespec a, b;
struct timespec64 a, b;
unsigned long irq_flags;
local_irq_save(irq_flags);
getnstimeofday(&a);
ktime_get_real_ts64(&a);
port->ops->write_control(port, NO_SIGNAL);
getnstimeofday(&b);
ktime_get_real_ts64(&b);
local_irq_restore(irq_flags);
b = timespec_sub(b, a);
acc += timespec_to_ns(&b);
b = timespec64_sub(b, a);
acc += timespec64_to_ns(&b);
}
dev->port_write_time = acc >> PORT_NTESTS_SHIFT;
@ -180,9 +180,9 @@ static void calibrate_port(struct pps_generator_pp *dev)
static inline ktime_t next_intr_time(struct pps_generator_pp *dev)
{
struct timespec ts;
struct timespec64 ts;
getnstimeofday(&ts);
ktime_get_real_ts64(&ts);
return ktime_set(ts.tv_sec +
((ts.tv_nsec > 990 * NSEC_PER_MSEC) ? 1 : 0),