[PATCH v3 1/1] pps: clients: gpio: Bypass edge's direction check when not needed

[Bastien Curutchet <bastien.curutchet@bootlin.com>]

In the IRQ handler, the GPIO's state is read to verify the direction of
the edge that triggered the interruption before generating the PPS event.
If a pulse is too short, the GPIO line can reach back its original state
before this verification and the PPS event is lost.

This check is needed when info->capture_clear is set because it needs
interruptions on both rising and falling edges. When info->capture_clear
is not set, interruption is triggered by one edge only so this check can
be omitted.

Add a warning if irq_handler is left without triggering any PPS event.
Bypass the edge's direction verification when info->capture_clear is not
set.

Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>
---
Changes in v3:
 - Add a warning in irq_handler
Changes in v2:
 - Modifiy the way the bypass is done to avoid code duplication

v1: https://lore.kernel.org/all/20240410113502.73038-1-bastien.curutchet@bootlin.com/
v2: https://lore.kernel.org/all/20240411061329.7262-1-bastien.curutchet@bootlin.com/

 drivers/pps/clients/pps-gpio.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c
index 2f4b11b4dfcd..af62d944d051 100644
--- a/drivers/pps/clients/pps-gpio.c
+++ b/drivers/pps/clients/pps-gpio.c
@@ -52,7 +52,9 @@ static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
 
 	info = data;
 
-	rising_edge = gpiod_get_value(info->gpio_pin);
+	/* Small trick to bypass the check on edge's direction when capture_clear is unset */
+	rising_edge = info->capture_clear ?
+		      gpiod_get_value(info->gpio_pin) : !info->assert_falling_edge;
 	if ((rising_edge && !info->assert_falling_edge) ||
 			(!rising_edge && info->assert_falling_edge))
 		pps_event(info->pps, &ts, PPS_CAPTUREASSERT, data);
@@ -60,6 +62,8 @@ static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
 			((rising_edge && info->assert_falling_edge) ||
 			(!rising_edge && !info->assert_falling_edge)))
 		pps_event(info->pps, &ts, PPS_CAPTURECLEAR, data);
+	else
+		dev_warn_ratelimited(info->pps->dev, "IRQ did not trigger any PPS event\n");
 
 	return IRQ_HANDLED;
 }
-- 
2.44.0