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

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Date: Wed, 10 Apr 2024 16:23:43 +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
Subject: Re: [PATCH 1/1] pps: clients: gpio: Bypass edge's direction check
 when not needed

On 10/04/24 13:35, 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.
> 
> Bypass the edge's direction verification when info->capture_clear is not
> set.
> 
> Signed-off-by: Bastien Curutchet <bastien.curutchet@...tlin.com>
> ---
>   drivers/pps/clients/pps-gpio.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/pps/clients/pps-gpio.c b/drivers/pps/clients/pps-gpio.c
> index 2f4b11b4dfcd..c2a96e3e3836 100644
> --- a/drivers/pps/clients/pps-gpio.c
> +++ b/drivers/pps/clients/pps-gpio.c
> @@ -52,6 +52,15 @@ static irqreturn_t pps_gpio_irq_handler(int irq, void *data)
>   
>   	info = data;
>   
> +	if (!info->capture_clear) {
> +		/*
> +		 * If capture_clear is unset, IRQ is triggered by one edge only.
> +		 * So the check on edge direction is not needed here
> +		 */
> +		pps_event(info->pps, &ts, PPS_CAPTUREASSERT, data);
> +		return IRQ_HANDLED;
> +	}
> +
>   	rising_edge = gpiod_get_value(info->gpio_pin);
>   	if ((rising_edge && !info->assert_falling_edge) ||
>   			(!rising_edge && info->assert_falling_edge))

Apart the code duplication, which are the real benefits of doing so?

Rodolfo

-- 
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