From: Florian Fainelli <f.fainelli@gmail.com>
To: Jia-Ju Bai <baijiaju1990@gmail.com>,
Phil Reid <preid@electromag.com.au>,
andrew@lunn.ch, vivien.didelot@savoirfairelinux.com
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: dsa: b53: Replace mdelay with msleep in b53_switch_reset_gpio
Date: Wed, 11 Apr 2018 09:19:04 -0700 [thread overview]
Message-ID: <7d376874-8078-0252-ed7e-29392a519fc8@gmail.com> (raw)
In-Reply-To: <7c9dffb7-d55a-98f5-4024-7e2f0c704a56@gmail.com>
On 04/11/2018 12:14 AM, Jia-Ju Bai wrote:
>
>
> On 2018/4/11 13:30, Phil Reid wrote:
>> 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?
>>
>
> Yes, I think gpio_set_value_cansleep() is okay here?
> Do I need to send a V2 patch to replace gpio_set_value()?
Yes, I would lump these two changes in the same patch since this is
effectively about solving sleeping vs. non sleeping operations.
Thanks!
--
Florian
next prev parent reply other threads:[~2018-04-11 16:19 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-11 1:51 [PATCH] net: dsa: b53: Replace mdelay with msleep in b53_switch_reset_gpio Jia-Ju Bai
2018-04-11 5:30 ` Phil Reid
2018-04-11 7:14 ` Jia-Ju Bai
2018-04-11 16:19 ` Florian Fainelli [this message]
2018-04-12 1:49 ` Jia-Ju Bai
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