linux-kernel - Re: [PATCH net] net: dsa: qca8k: fix illegal usage of GPIO

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Date: Wed, 24 Jan 2024 10:47:32 +0100
From: Michal Vokáč <michal.vokac@...ft.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: "David S. Miller" <davem@...emloft.net>,
 Florian Fainelli <f.fainelli@...il.com>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Christian Lamparter <chunkeey@...il.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, petr.benes@...ft.com,
 Vladimir Oltean <olteanv@...il.com>, Christian Marangi
 <ansuelsmth@...il.com>, "Russell King (Oracle)"
 <rmk+kernel@...linux.org.uk>, Marek Behún
 <kabel@...nel.org>, Jiasheng Jiang <jiasheng@...as.ac.cn>
Subject: Re: [PATCH net] net: dsa: qca8k: fix illegal usage of GPIO

On 24. 01. 24 0:07, Andrew Lunn wrote:
> On Mon, Jan 22, 2024 at 01:04:09PM +0100, Michal Vokáč wrote:
>> When working with GPIO, its direction must be set either when the GPIO is
>> requested by gpiod_get*() or later on by one of the gpiod_direction_*()
>> functions. Neither of this is done here which result in undefined behavior
>> on some systems.
>>
>> As the reset GPIO is used right after it is requested here, it makes sense
>> to configure it as GPIOD_OUT_HIGH right away.
>> Fixes: a653f2f538f9 ("net: dsa: qca8k: introduce reset via gpio feature")
>> Signed-off-by: Michal Vokáč <michal.vokac@...ft.com>
>> ---
>>   drivers/net/dsa/qca/qca8k-8xxx.c | 3 +--
>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/dsa/qca/qca8k-8xxx.c b/drivers/net/dsa/qca/qca8k-8xxx.c
>> index 4ce68e655a63..83b19c2d7b97 100644
>> --- a/drivers/net/dsa/qca/qca8k-8xxx.c
>> +++ b/drivers/net/dsa/qca/qca8k-8xxx.c
>> @@ -2037,8 +2037,7 @@ qca8k_sw_probe(struct mdio_device *mdiodev)
>>   	priv->dev = &mdiodev->dev;
>>   	priv->info = of_device_get_match_data(priv->dev);
>>   
>> -	priv->reset_gpio = devm_gpiod_get_optional(priv->dev, "reset",
>> -						   GPIOD_ASIS);
>> +	priv->reset_gpio = devm_gpiod_get_optional(priv->dev, "reset", GPIOD_OUT_HIGH);
>>   	if (IS_ERR(priv->reset_gpio))
>>   		return PTR_ERR(priv->reset_gpio);
> 
> Hi Michal
> 
> So the current code is:
> 
> 	priv->reset_gpio = devm_gpiod_get_optional(priv->dev, "reset",
> 						   GPIOD_ASIS);
> 	if (IS_ERR(priv->reset_gpio))
> 		return PTR_ERR(priv->reset_gpio);
> 
> 	if (priv->reset_gpio) {
> 		gpiod_set_value_cansleep(priv->reset_gpio, 1);
> 		/* The active low duration must be greater than 10 ms
> 		 * and checkpatch.pl wants 20 ms.
> 		 */
> 		msleep(20);
> 		gpiod_set_value_cansleep(priv->reset_gpio, 0);
> 	}
> 
> Doesn't your change make the gpiod_set_value_cansleep() pointless?
> 
> Please extend your patch to remove it, maybe extending the comment a
> little.

Hi Andrew,
I agree, in this case the call to gpiod_set_value(1) is now pointless.
I will remove it and describe the change.

> Please also make sure what v2 Is Cc: to the qca8k Maintainers.

I wonder who do you mean by qca8k maintainers? There is no one explicitly
stated as a qca8k driver maintainer in MAINTAINERS file.

I admit that there is couple of people listed in get_maintainer output
as authors/commit signers that I have not Cc'd. I have added them to
the Cc list now and will do in the v2 as well.

Thanks for the comments!
Michal