linux-kernel - Re: [PATCH V3 4/4] gpio: tegra: Add support for gpio debounce

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Message-ID: <57191D8A.9040704@wwwdotorg.org>
Date:	Thu, 21 Apr 2016 12:35:54 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Laxman Dewangan <ldewangan@...dia.com>
Cc:	linus.walleij@...aro.org, gnurou@...il.com,
	thierry.reding@...il.com, linux-gpio@...r.kernel.org,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 4/4] gpio: tegra: Add support for gpio debounce

On 04/20/2016 07:30 AM, Laxman Dewangan wrote:
> NVIDIA's Tegra210 support the HW debounce in the GPIO
> controller for all its GPIO pins.
>
> Add support for setting debounce timing by implementing the
> set_debounce callback of gpiochip.

> diff --git a/drivers/gpio/gpio-tegra.c b/drivers/gpio/gpio-tegra.c

> +static int tegra_gpio_set_debounce(struct gpio_chip *chip, unsigned int offset,

> +	/* There is only one debounce count register per port and hence
> +	 * set the maximum of current and requested debounce time.
> +	 */
> +	if (tgi->bank_info[bank].dbc_cnt[port] < debounce_ms) {
> +		tegra_gpio_writel(tgi, debounce_ms, GPIO_DBC_CNT(tgi, offset));
> +		tgi->bank_info[bank].dbc_cnt[port] = debounce_ms;
> +	}

Do we need any locking there? I imagine the GPIO core doesn't prevent 
different threads/drivers from manipulating different GPIOs in parallel 
on different cores.