linux-kernel - Re: [PATCH V2 3/3] gpio: tegra: Add support for gpio debounce

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Date:	Tue, 19 Apr 2016 11:43:25 +0100
From:	Jon Hunter <jonathanh@...dia.com>
To:	Laxman Dewangan <ldewangan@...dia.com>, <linus.walleij@...aro.org>,
	<gnurou@...il.com>, <swarren@...dotorg.org>,
	<thierry.reding@...il.com>
CC:	<linux-gpio@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 3/3] gpio: tegra: Add support for gpio debounce


On 19/04/16 10:43, 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.
> 
> Signed-off-by: Laxman Dewangan <ldewangan@...dia.com>
> 
> ---
> Changes from V1:
> - Write debounce count before enable.
> - Make sure the debounce count do not have any boot residuals.
> ---
>  drivers/gpio/gpio-tegra.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)

[snip]

> @@ -327,6 +360,9 @@ static int tegra_gpio_resume(struct device *dev)
>  			tegra_gpio_writel(bank->oe[p], GPIO_OE(gpio));
>  			tegra_gpio_writel(bank->int_lvl[p], GPIO_INT_LVL(gpio));
>  			tegra_gpio_writel(bank->int_enb[p], GPIO_INT_ENB(gpio));
> +			tegra_gpio_writel(bank->dbc_cnt[p], GPIO_DBC_CNT(gpio));
> +			tegra_gpio_writel(bank->dbc_enb[p],
> +					  GPIO_MSK_DBC_EN(gpio));

If these registers are not valid on Tegra devices prior to Tegra210, I
don't think we should write to these locations on those devices (even if
we are writing back the values read).

> @@ -351,6 +387,10 @@ static int tegra_gpio_suspend(struct device *dev)
>  			bank->oe[p] = tegra_gpio_readl(GPIO_OE(gpio));
>  			bank->int_enb[p] = tegra_gpio_readl(GPIO_INT_ENB(gpio));
>  			bank->int_lvl[p] = tegra_gpio_readl(GPIO_INT_LVL(gpio));
> +			bank->dbc_enb[p] = tegra_gpio_readl(
> +							GPIO_MSK_DBC_EN(gpio));
> +			bank->dbc_enb[p] = (bank->dbc_enb[p] << 8) ||
> +						bank->dbc_enb[p];

Same here, not sure we should even bother reading these for Tegra's
before Tegra210.

Cheers
Jon