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Subject: Re: [PATCH] net: dsa: b53: Replace mdelay with msleep in
 b53_switch_reset_gpio
To:     Jia-Ju Bai <baijiaju1990@gmail.com>, f.fainelli@gmail.com,
        andrew@lunn.ch, vivien.didelot@savoirfairelinux.com
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <1523411485-2030-1-git-send-email-baijiaju1990@gmail.com>
From:   Phil Reid <preid@electromag.com.au>
Message-ID: <11d079ab-3c07-a10d-c321-f873c53e9690@electromag.com.au>
Date:   Wed, 11 Apr 2018 13:30:11 +0800
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On 11/04/2018 09:51, Jia-Ju Bai wrote:
> b53_switch_reset_gpio() is never called in atomic context.
> 
> The call chain ending up at b53_switch_reset_gpio() is:
> [1] b53_switch_reset_gpio() <- b53_switch_reset() <-
> 	b53_reset_switch() <- b53_setup()
> 
> b53_switch_reset_gpio() is set as ".setup" in struct dsa_switch_ops.
> This function is not called in atomic context.
> 
> Despite never getting called from atomic context, b53_switch_reset_gpio()
> calls mdelay() to busily wait.
> This is not necessary and can be replaced with msleep() to
> avoid busy waiting.
> 
> This is found by a static analysis tool named DCNS written by myself.
> And I also manually check it.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
> ---
>   drivers/net/dsa/b53/b53_common.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
> index 274f367..e070ff6 100644
> --- a/drivers/net/dsa/b53/b53_common.c
> +++ b/drivers/net/dsa/b53/b53_common.c
> @@ -597,10 +597,10 @@ static void b53_switch_reset_gpio(struct b53_device *dev)
>   	/* Reset sequence: RESET low(50ms)->high(20ms)
>   	 */
>   	gpio_set_value(gpio, 0);
> -	mdelay(50);
> +	msleep(50);
>   
>   	gpio_set_value(gpio, 1);
> -	mdelay(20);
> +	msleep(20);
>   
>   	dev->current_page = 0xff;
>   }
> 
Would that also imply gpio_set_value could be gpio_set_value_cansleep?


-- 
Regards
Phil Reid