pps: pps-gpio: split IRQ handler into hardirq timestamper + threaded handler

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Split the pps-gpio interrupt handler into a primary (hardirq) handler that
captures the PPS timestamp at interrupt entry, and a threaded handler that
processes the event.  This produces the same two-part handler structure on
both PREEMPT_RT and non-RT kernels.

On non-RT kernels the threaded portion runs immediately after the primary,
with no behavioral change compared to the previous single-handler
implementation.

On PREEMPT_RT, where interrupt handlers are force-threaded by default, the
previous single-handler implementation captured the timestamp inside the
threaded portion, after IRQ-thread scheduling delay.  With the split, the
timestamp is captured in true hardirq context as it is on non-RT kernels,
eliminating a significant source of PPS jitter on RT systems.

Link: https://lore.kernel.org/2e32729029fbf6977ecf04665eb00f2efd3e2c17.1780359378.git.calvin@wbinvd.org
Signed-off-by: Michael Byczkowski <by@by-online.de>
Signed-off-by: Calvin Owens <calvin@wbinvd.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Michael Byczkowski <by@by-online.de>
Tested-by: Calvin Owens <calvin@wbinvd.org>
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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This commit is contained in:

Michael Byczkowski 2026-06-01 17:44:09 -07:00 • committed by Andrew Morton

parent 8fdcbb5b37

commit 93781560b2

1 changed files with 25 additions and 12 deletions

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drivers/pps/clients/pps-gpio.c

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