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

From: Phil Reid
Date: Wed Apr 11 2018 - 22:31:46 EST


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@xxxxxxxxx>
---
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@xxxxxxxxxxxxxxxxx>