[PATCH v2] net: dsa: b53: Using sleep-able operations in b53_switch_reset_gpio

[PATCH v2] net: dsa: b53: Using sleep-able operations in b53_switch_reset_gpio

[Jia-Ju Bai]

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@gmail.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;
 }
-- 
1.9.1

Re: [PATCH v2] net: dsa: b53: Using sleep-able operations in b53_switch_reset_gpio

[Phil Reid]

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@gmail.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@electromag.com.au>

Re: [PATCH v2] net: dsa: b53: Using sleep-able operations in b53_switch_reset_gpio

[Florian Fainelli]

On 04/11/2018 06:48 PM, 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@gmail.com>

Acked-by: Florian Fainelli <f.fainelli@gmail.com>

-- 
Florian