linux-kernel - Re: [PATCH v2] gpio: rockchip: resolve underflow issue

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Message-ID: <Zsih2NggJXRF6YhI@smile.fi.intel.com>
Date: Fri, 23 Aug 2024 17:51:04 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Ye Zhang <ye.zhang@...k-chips.com>
Cc: linus.walleij@...aro.org, brgl@...ev.pl, heiko@...ech.de,
	linux-gpio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
	mika.westerberg@...ux.intel.com, tao.huang@...k-chips.com,
	finley.xiao@...k-chips.com, tim.chen@...k-chips.com,
	elaine.zhang@...k-chips.com
Subject: Re: [PATCH v2] gpio: rockchip: resolve underflow issue

On Fri, Aug 23, 2024 at 11:43:07AM +0800, Ye Zhang wrote:
> div_reg may be < 0 if debounce is zero, causing the unsigned int to
> overflow.

...

> -	if (bank->gpio_type == GPIO_TYPE_V2 && !IS_ERR(bank->db_clk)) {
> -		div_debounce_support = true;

Wouldn't be cleaner (from the patch perspective) to simply move else branch here?

	else
		div_debounce_support = false;

> +	div_debounce_support = (bank->gpio_type == GPIO_TYPE_V2) && !IS_ERR(bank->db_clk);
> +	if (debounce && div_debounce_support) {
>  		freq = clk_get_rate(bank->db_clk);
>  		if (!freq)
>  			return -EINVAL;
> @@ -216,8 +216,6 @@ static int rockchip_gpio_set_debounce(struct gpio_chip *gc,
>  
>  		div = (u64)debounce * freq;
>  		div_reg = DIV_ROUND_CLOSEST_ULL(div, 2 * USEC_PER_SEC) - 1;
> -	} else {
> -		div_debounce_support = false;
>  	}

-- 
With Best Regards,
Andy Shevchenko