Received-SPF: pass (google.com: domain of linux-kernel+bounces-66614-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Message-ID: <d51dbac55d3677031bfab8bfe959f7b556b1c373.camel@pengutronix.de>
Subject: Re: [PATCH 19/23] gpio: nomadik: grab optional reset control and
 deassert it at probe
From: Philipp Zabel <p.zabel@pengutronix.de>
To: =?ISO-8859-1?Q?Th=E9o?= Lebrun <theo.lebrun@bootlin.com>, Linus Walleij
 <linus.walleij@linaro.org>, Bartosz Golaszewski <brgl@bgdev.pl>, Rob
 Herring <robh+dt@kernel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@linaro.org>,  Conor Dooley <conor+dt@kernel.org>,
 Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: linux-gpio@vger.kernel.org, devicetree@vger.kernel.org, 
 linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, 
 linux-mips@vger.kernel.org, Gregory CLEMENT <gregory.clement@bootlin.com>, 
 Vladimir Kondratiev <vladimir.kondratiev@mobileye.com>, Thomas Petazzoni
 <thomas.petazzoni@bootlin.com>, Tawfik Bayouk <tawfik.bayouk@mobileye.com>
Date: Thu, 15 Feb 2024 11:19:14 +0100
In-Reply-To: <20240214-mbly-gpio-v1-19-f88c0ccf372b@bootlin.com>
References: <20240214-mbly-gpio-v1-0-f88c0ccf372b@bootlin.com>
	 <20240214-mbly-gpio-v1-19-f88c0ccf372b@bootlin.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.46.4-2 
Precedence: bulk
MIME-Version: 1.0

On Mi, 2024-02-14 at 17:24 +0100, Th=C3=A9o Lebrun wrote:
> Fetch a reference to the optional shared reset control and deassert it
> if it exists.
>=20
> Optional because not all platforms that use this driver have a reset
> attached to the reset block. Shared because some platforms that use the
> reset (at least Mobileye EyeQ5) share the reset across banks.
>=20
> Do not keep a reference to the reset control as it is not needed
> afterwards; the driver does not handle suspend, does not use runtime PM
> and does not register a remove callback.

I suppose you don't care that the reset is only ever deasserted once
and never asserted again on this hardware, but for shared reset
controls the expectation is that deassert/assert calls are balanced:

https://docs.kernel.org/driver-api/reset.html?highlight=3Dbalanced#assertio=
n-and-deassertion

So maybe this warrants a comment in the code. Or do you mean to
suppress unbind via suppress_bind_attrs to explain away any missing
cleanup?

> The operation is done in nmk_gpio_populate_chip(). This function is
> called by either gpio-nomadik or pinctrl-nomadik, whoever comes first.
> This is here for historic reasons and could probably be removed now; it
> seems gpio-ranges enforces the ordering to be pinctrl-first. It is not
> the topic of the present patch however.
>=20
> Signed-off-by: Th=C3=A9o Lebrun <theo.lebrun@bootlin.com>
> ---
>  drivers/gpio/gpio-nomadik.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>=20
> diff --git a/drivers/gpio/gpio-nomadik.c b/drivers/gpio/gpio-nomadik.c
> index 21bb6d6363fc..b623c093b54d 100644
> --- a/drivers/gpio/gpio-nomadik.c
> +++ b/drivers/gpio/gpio-nomadik.c
> @@ -513,12 +513,14 @@ struct nmk_gpio_chip *nmk_gpio_populate_chip(struct=
 device_node *np,
>  {
>  	struct nmk_gpio_chip *nmk_chip;
>  	struct platform_device *gpio_pdev;
> +	struct reset_control *reset;
>  	struct gpio_chip *chip;
>  	struct resource *res;
>  	struct clk *clk;
>  	void __iomem *base;
>  	uintptr_t flags;
>  	u32 id, ngpio;
> +	int ret;
> =20
>  	gpio_pdev =3D of_find_device_by_node(np);
>  	if (!gpio_pdev) {
> @@ -576,6 +578,19 @@ struct nmk_gpio_chip *nmk_gpio_populate_chip(struct =
device_node *np,
>  	clk_prepare(clk);
>  	nmk_chip->clk =3D clk;
> =20
> +	reset =3D devm_reset_control_get_optional_shared(&gpio_pdev->dev, NULL)=
;
> +	if (IS_ERR(reset)) {
> +		dev_err(&pdev->dev, "failed getting reset control: %ld\n",
> +			PTR_ERR(reset));
> +		return ERR_CAST(reset);

Consider using dev_err_probe() here.

regards
Philipp