linux-kernel - Re: [PATCH v2] net: dsa: b53: Using sleep-able operations in b53_switch_reset

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Date:   Thu, 12 Apr 2018 10:31:22 +0800
From:   Phil Reid <preid@...ctromag.com.au>
To:     Jia-Ju Bai <baijiaju1990@...il.com>, f.fainelli@...il.com,
        andrew@...n.ch, vivien.didelot@...oirfairelinux.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: dsa: b53: Using sleep-able operations in
 b53_switch_reset_gpio

On 12/04/2018 09:48, 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 non-sleep operations mdelay() and gpio_set_value().
> They are not necessary and can be replaced with msleep()
> and gpio_set_value_cansleep().
> 
> 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@...il.com>
> ---
> v2:
> * Use gpio_set_value_cansleep() to replace gpio_set_value() additionally.
>    Thanks for Florian and Phil for good advice.
> ---
>   drivers/net/dsa/b53/b53_common.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/dsa/b53/b53_common.c b/drivers/net/dsa/b53/b53_common.c
> index 274f367..36cc60d 100644
> --- a/drivers/net/dsa/b53/b53_common.c
> +++ b/drivers/net/dsa/b53/b53_common.c
> @@ -596,11 +596,11 @@ static void b53_switch_reset_gpio(struct b53_device *dev)
>   
>   	/* Reset sequence: RESET low(50ms)->high(20ms)
>   	 */
> -	gpio_set_value(gpio, 0);
> -	mdelay(50);
> +	gpio_set_value_cansleep(gpio, 0);
> +	msleep(50);
>   
> -	gpio_set_value(gpio, 1);
> -	mdelay(20);
> +	gpio_set_value_cansleep(gpio, 1);
> +	msleep(20);
>   
>   	dev->current_page = 0xff;
>   }
> 

FWIW:
Reviewed-by: Phil Reid <preid@...ctromag.com.au>