diff mbox series

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

Message ID 20240214-mbly-gpio-v1-19-f88c0ccf372b@bootlin.com (mailing list archive)
State Superseded
Headers show
Series Rework Nomadik GPIO to add Mobileye EyeQ5 support | expand

Commit Message

Théo Lebrun Feb. 14, 2024, 4:24 p.m. UTC
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.

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(+)

Comments

Philipp Zabel Feb. 15, 2024, 10:19 a.m. UTC | #1
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
Théo Lebrun Feb. 16, 2024, 10:46 a.m. UTC | #2
Hello,

On Thu Feb 15, 2024 at 11:19 AM CET, Philipp Zabel wrote:
> 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?

Those resets are shared only across GPIO banks which have no reason to
be unbind-able. I'll add a comment and disable unbind.

> > 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.

Makes sense, will do so for next revision.

Thanks for the review Philipp,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
diff mbox series

Patch

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);
+	}
+
+	ret = reset_control_deassert(reset);
+	if (ret) {
+		dev_err(&pdev->dev, "failed reset deassert: %d\n", ret);
+		return ERR_PTR(ret);
+	}
+
 #ifdef CONFIG_PINCTRL_NOMADIK
 	BUG_ON(nmk_chip->bank >= ARRAY_SIZE(nmk_gpio_chips));
 	nmk_gpio_chips[id] = nmk_chip;