linux-kernel - Re: [PATCH] power: reset: piix4-poweroff: Replace mdelay() with msleep() and usleep_range() in piix4

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Message-ID: <20180829224456.3iadf2hnv5pxlms4@earth.universe>
Date:   Thu, 30 Aug 2018 00:44:56 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] power: reset: piix4-poweroff: Replace mdelay() with
 msleep() and usleep_range() in piix4_poweroff()

Hi,

On Mon, Jul 30, 2018 at 09:48:38PM +0800, Jia-Ju Bai wrote:
> piix4_poweroff() is never called in atomic context.
> It calls mdelay() to busily wait, which is not necessary.
> mdelay() can be replaced with msleep() and usleep_range().
> 
> This is found by a static analysis tool named DCNS written by myself.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
> ---

This is a shutdown driver, so busy waiting is ok.

-- Sebastian

>  drivers/power/reset/piix4-poweroff.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/power/reset/piix4-poweroff.c b/drivers/power/reset/piix4-poweroff.c
> index 20ce3ff5e039..5d4c72992d2c 100644
> --- a/drivers/power/reset/piix4-poweroff.c
> +++ b/drivers/power/reset/piix4-poweroff.c
> @@ -47,7 +47,7 @@ static void piix4_poweroff(void)
>  	     io_offset + PIIX4_FUNC3IO_PMCNTRL);
>  
>  	/* If the special cycle occurs too soon this doesn't work... */
> -	mdelay(10);
> +	usleep_range(10000, 11000);
>  
>  	/*
>  	 * The PIIX4 will enter the suspend state only after seeing a special
> @@ -59,7 +59,7 @@ static void piix4_poweroff(void)
>  				   PIIX4_SUSPEND_MAGIC);
>  
>  	/* Give the system some time to power down, then error */
> -	mdelay(1000);
> +	msleep(1000);
>  	pr_emerg("Unable to poweroff system\n");
>  }
>  
> -- 
> 2.17.0
> 

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