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

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Date: Thu, 25 Apr 2024 14:42:40 +0200
From: Rodolfo Giometti <giometti@...eenne.com>
To: Bastien Curutchet <bastien.curutchet@...tlin.com>
Cc: linux-kernel@...r.kernel.org,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, herve.codina@...tlin.com,
 christophercordahi@...ometrics.ca,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 1/1] pps: clients: gpio: Bypass edge's direction check
 when not needed

On 25/04/24 14:28, Bastien Curutchet wrote:
> 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@...tlin.com>

Acked-by: Rodolfo Giometti <giometti@...eenne.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;
>   }

-- 
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