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

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Date: Wed, 24 Jan 2024 00:07:33 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Michal Vokáč <michal.vokac@...ft.com>
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
Subject: Re: [PATCH net] net: dsa: qca8k: fix illegal usage of GPIO

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.

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

    Andrew

---
pw-bot: cr