Re: [PATCH 19/23] gpio: nomadik: grab optional reset control and deassert it at probe

Philipp Zabel
2024-02-15T10:19:23Z

On Mi, 2024-02-14 at 17:24 +0100, Théo Lebrun wrote:
> Fetch a reference to the optional shared reset control and deassert it
> if it exists.
>
> 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.
>
> 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=balanced#assertion-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.
>
> Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
> ---
> drivers/gpio/gpio-nomadik.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> 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;
>
> gpio_pdev = 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 = clk;
>
> + reset = 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