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gpiolib: fix line event timestamps for nested irqs 

Nested interrupts run inside the calling thread's context and the top
half handler is never called which means that we never read the
timestamp.

This issue came up when trying to read line events from a gpiochip
using regmap_irq_chip for interrupts.

Fix it by reading the timestamp from the irq thread function if it's
still 0 by the time the second handler is called.

Fixes: d58f2bf261 ("gpio: Timestamp events in hardirq handler")
Cc: stable@vger.kernel.org
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
hifive-unleashed-5.1
Bartosz Golaszewski 2019-01-04 11:24:20 +01:00
parent 2486e67374
commit 1033be5899
1 changed files with 8 additions and 1 deletions
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9
drivers/gpio/gpiolib.c
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@ -828,7 +828,14 @@ static irqreturn_t lineevent_irq_thread(int irq, void *p)
/* Do not leak kernel stack to userspace */
memset(&ge, 0, sizeof(ge));
ge.timestamp = le->timestamp;
/*
* We may be running from a nested threaded interrupt in which case
* we didn't get the timestamp from lineevent_irq_handler().
*/
if (!le->timestamp)
ge.timestamp = ktime_get_real_ns();
else
ge.timestamp = le->timestamp;
if (le->eflags & GPIOEVENT_REQUEST_RISING_EDGE
&& le->eflags & GPIOEVENT_REQUEST_FALLING_EDGE) {