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authorLinus Walleij <linus.walleij@linaro.org>2020-02-20 15:56:24 +0100
committerLinus Walleij <linus.walleij@linaro.org>2020-02-21 16:29:38 +0100
commitf8850206e160bfe35de9ca2e726ab6d6b8cb77dd (patch)
tree544a8700772a327087c3a86815d2a8a465842ad2 /drivers
parent1739a2d852265977836152be43073ead5c64d1ea (diff)
gpio: Switch timestamps to ktime_get_ns()
The existing use of ktime_get_real_ns() in the timestamps from the GPIO events is dubious. We have had several discussions about this timestamp, and it is unclear whether userspace has ever taken into account that a timestamp from ktime_get_real_ns() can actually move backwards in time relative the previous timetamp, and userspace is more likely to expect a monotonic counter. Background: https://lore.kernel.org/linux-gpio/CAK8P3a1Skvm48sje8FNDPLYqyz9Lf8q0qX1QETWtyZTxuX4k1g@mail.gmail.com/ https://marc.info/?l=linux-gpio&m=151661955709074&w=2 The change is ABI incompatible, but incompatible in a way that is IMO more likely to fix future bugs rather than break current userspace. To the best of my knowledge all userspace expects a monotonic timestamp and users are just lucky that they very seldom move backwards in time. Cc: Arnd Bergmann <arnd@arndb.de> Acked-by: Bartosz Golaszewski <bgolaszewski@baylibre.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/gpio/gpiolib.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 611709fd560f..2c3a9c1c76be 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -954,7 +954,7 @@ static irqreturn_t lineevent_irq_thread(int irq, void *p)
* we didn't get the timestamp from lineevent_irq_handler().
*/
if (!le->timestamp)
- ge.timestamp = ktime_get_real_ns();
+ ge.timestamp = ktime_get_ns();
else
ge.timestamp = le->timestamp;
@@ -995,7 +995,7 @@ static irqreturn_t lineevent_irq_handler(int irq, void *p)
* Just store the timestamp in hardirq context so we get it as
* close in time as possible to the actual event.
*/
- le->timestamp = ktime_get_real_ns();
+ le->timestamp = ktime_get_ns();
return IRQ_WAKE_THREAD;
}