linux-kernel - Re: [PATCH] clockevents: timer-stm32: Fix build warning spotted by kbuild test robot

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Date:	Thu, 28 May 2015 00:52:14 +0200
From:	Luc Van Oostenryck <luc.vanoostenryck@...il.com>
To:	Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, fengguang.wu@...el.com
Subject: Re: [PATCH] clockevents: timer-stm32: Fix build warning spotted by
 kbuild test robot

On Wed, May 27, 2015 at 06:41:23PM +0200, Maxime Coquelin wrote:
> This patch fixes below warning spotted by kbuild test robot when building
> with ARCH=powerpc:
> 
>    drivers/clocksource/timer-stm32.c: In function 'stm32_clockevent_init':
> >> drivers/clocksource/timer-stm32.c:140:9: warning: large integer implicitly truncated to unsigned type [-Woverflow]
>      writel_relaxed(~0UL, data->base + TIM_ARR);
> 
> The fix consists in casting the value to u32.
> 
> Reported-by: kbuild test robot <fengguang.wu@...el.com>
> Signed-off-by: Maxime Coquelin <mcoquelin.stm32@...il.com>
> ---
>  drivers/clocksource/timer-stm32.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clocksource/timer-stm32.c b/drivers/clocksource/timer-stm32.c
> index fad2e2e..c9578d8 100644
> --- a/drivers/clocksource/timer-stm32.c
> +++ b/drivers/clocksource/timer-stm32.c
> @@ -137,7 +137,7 @@ static void __init stm32_clockevent_init(struct device_node *np)
>  	}
>  
>  	/* Detect whether the timer is 16 or 32 bits */
> -	writel_relaxed(~0UL, data->base + TIM_ARR);
> +	writel_relaxed((u32)~0UL, data->base + TIM_ARR);
>  	max_delta = readl_relaxed(data->base + TIM_ARR);
>  	if (max_delta == ~0UL) {
>  		prescaler = 1;


Since the warning come from using a unsigned long constant while
writel() expect an unsigned int, why not simply use ~0U ?


Luc Van Oostenryck
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