linux-kernel - Re: [PATCH 1/1] extcon: gpio: queue work only if debounce is NZ

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Date:	Tue, 8 Mar 2016 06:51:21 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Venkat Reddy Talla <vreddytalla@...dia.com>
Cc:	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	linux-kernel@...r.kernel.org,
	Laxman Dewangan <ldewangan@...dia.com>
Subject: Re: [PATCH 1/1] extcon: gpio: queue work only if debounce is NZ

On Tue, Mar 08, 2016 at 05:15:53PM +0530, Venkat Reddy Talla wrote:
> Use queue_delayed_work only when debounce time is
> required to read gpio state properly, read the gpio
> state and set the extcon cable state in IRQ handler
> context if gpio settling time is not needed.
> 
> Signed-off-by: Venkat Reddy Talla <vreddytalla@...dia.com>
> ---
>  drivers/extcon/extcon-gpio.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/extcon/extcon-gpio.c b/drivers/extcon/extcon-gpio.c
> index 279ff8f..1beb086 100644
> --- a/drivers/extcon/extcon-gpio.c
> +++ b/drivers/extcon/extcon-gpio.c
> @@ -56,8 +56,12 @@ static irqreturn_t gpio_irq_handler(int irq, void *dev_id)
>  {
>  	struct gpio_extcon_data *data = dev_id;
>  
> -	queue_delayed_work(system_power_efficient_wq, &data->work,
> +	if (data->debounce_jiffies)
> +		queue_delayed_work(system_power_efficient_wq, &data->work,
>  			      data->debounce_jiffies);
> +	else
> +		gpio_extcon_work(&data->work.work);
> +

The interrupt is requested with devm_request_any_context_irq(), meaning
the handler may run in hard interrupt context. gpio_extcon_work() calls
gpiod_get_value_cansleep(), which may not be a good idea in hard interrupt
context.

Guenter

>  	return IRQ_HANDLED;
>  }
>  
> -- 
> 2.1.4
> 
>