[PATCH v1 0/2] Fix Nvidia BlueField-3 GPIO access

[PATCH v1 0/2] Fix Nvidia BlueField-3 GPIO access

[Asmaa Mnebhi]

Fix Nvidia BlueField-3 GPIO access via libgpiod gpioset tool.
gpioset tool fails to modify the GPIO value due to the following:
1) the pinctrl-mlxbf3 driver defines mlxbf3_gpio_request_enable()
   to enable software to take control over a gpio. Only then can
   the gpio-mlxbf3 driver modify the direction and value of the
   gpio. mlxbf3_gpio_disable_free() gives control back to hardware
   and is called when the "gpioset" command is invoked.
   This cancels out the effort to change the GPIO value and
   direction. So mlxbf3_gpio_disable_free() needs to be removed.
2) the gpio-mlxbf3 driver calls gpiochip_generic_request() which
   calls mlxbf3_gpio_request_enable(). "pin_ranges" needs not to be
   empty for mlxbf3_gpio_request_enable() to be invoked. So
   gpio-mlxbf3 needs to populate "pin_ranges".

Asmaa Mnebhi (2):
  pinctrl: mlxbf3: Remove gpio_disable_free()
  gpio: mlxbf3: Support add_pin_ranges()

 drivers/gpio/gpio-mlxbf3.c       | 20 ++++++++++++++++++++
 drivers/pinctrl/pinctrl-mlxbf3.c | 14 --------------
 2 files changed, 20 insertions(+), 14 deletions(-)

-- 
2.30.1

[PATCH v1 1/2] pinctrl: mlxbf3: Remove gpio_disable_free()

[Asmaa Mnebhi]

Remove support for gpio_disable_free() because it is called when the libgpiod
command "gpiset" is invoked. This gives the GPIO control back to hardware which
cancels out the effort to set the GPIO value.

Reminder of the code flow to change a GPIO value from software:
1) All GPIOs are controlled by hardware by default
2) To change the GPIO value, enable software control via a mux.
3) Once software has control over the GPIO pin, the gpio-mlxbf3 driver
   will be able to change the direction and value of the GPIO.

When the user runs "gpioset gpiochip0 0=0" for example, the gpio
pin value should change from 1 to 0. In this case, mlxbf3_gpio_request_enable()
is called via gpiochip_generic_request(). The latter switches GPIO control from
hardware to software. Then the GPIO value is changed from 1 to 0. However,
gpio_disable_free() is also called which changes control back to hardware
which changes the GPIO value back to 1.

Fixes: d11f932808d ("pinctrl: mlxbf3: Add pinctrl driver support")
Signed-off-by: Asmaa Mnebhi <asmaa@nvidia.com>
---
 drivers/pinctrl/pinctrl-mlxbf3.c | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/drivers/pinctrl/pinctrl-mlxbf3.c b/drivers/pinctrl/pinctrl-mlxbf3.c
index d9944e6a0af9..0e852a0d5ec2 100644
--- a/drivers/pinctrl/pinctrl-mlxbf3.c
+++ b/drivers/pinctrl/pinctrl-mlxbf3.c
@@ -223,26 +223,12 @@ static int mlxbf3_gpio_request_enable(struct pinctrl_dev *pctldev,
 	return 0;
 }
 
-static void mlxbf3_gpio_disable_free(struct pinctrl_dev *pctldev,
-				    struct pinctrl_gpio_range *range,
-				    unsigned int offset)
-{
-	struct mlxbf3_pinctrl *priv = pinctrl_dev_get_drvdata(pctldev);
-
-	/* disable GPIO functionality by giving control back to hardware */
-	if (offset < MLXBF3_NGPIOS_GPIO0)
-		writel(BIT(offset), priv->fw_ctrl_clr0);
-	else
-		writel(BIT(offset % MLXBF3_NGPIOS_GPIO0), priv->fw_ctrl_clr1);
-}
-
 static const struct pinmux_ops mlxbf3_pmx_ops = {
 	.get_functions_count = mlxbf3_pmx_get_funcs_count,
 	.get_function_name = mlxbf3_pmx_get_func_name,
 	.get_function_groups = mlxbf3_pmx_get_groups,
 	.set_mux = mlxbf3_pmx_set,
 	.gpio_request_enable = mlxbf3_gpio_request_enable,
-	.gpio_disable_free = mlxbf3_gpio_disable_free,
 };
 
 static struct pinctrl_desc mlxbf3_pin_desc = {
-- 
2.30.1

[PATCH v1 2/2] gpio: mlxbf3: Support add_pin_ranges()

[Asmaa Mnebhi]

Support add_pin_ranges() so that pinctrl_gpio_request() can be called.
The GPIO value is not modified when the user runs the "gpioset" tool.
This is because when gpiochip_generic_request is invoked by the gpio-mlxbf3
driver, "pin_ranges" is empty so it skips "pinctrl_gpio_request()".
pinctrl_gpio_request() is essential in the code flow because it changes the
mux value so that software has control over modifying the GPIO value.
Adding add_pin_ranges() creates a dependency on the pinctrl-mlxbf3.c driver.

Fixes: cd33f216d24 ("gpio: mlxbf3: Add gpio driver support")
Signed-off-by: Asmaa Mnebhi <asmaa@nvidia.com>
---
 drivers/gpio/gpio-mlxbf3.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/gpio/gpio-mlxbf3.c b/drivers/gpio/gpio-mlxbf3.c
index e30cee108986..3828f5282b17 100644
--- a/drivers/gpio/gpio-mlxbf3.c
+++ b/drivers/gpio/gpio-mlxbf3.c
@@ -158,6 +158,24 @@ static const struct irq_chip gpio_mlxbf3_irqchip = {
 	GPIOCHIP_IRQ_RESOURCE_HELPERS,
 };
 
+static int mlxbf3_gpio_add_pin_ranges(struct gpio_chip *chip)
+{
+	int ret;
+	int id = 0;
+
+	id = !!(chip->ngpio % MLXBF3_GPIO_MAX_PINS_PER_BLOCK);
+
+	ret = gpiochip_add_pin_range(chip,
+			"MLNXBF34:00",
+			chip->base,
+			id * MLXBF3_GPIO_MAX_PINS_PER_BLOCK,
+			chip->ngpio);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
 static int mlxbf3_gpio_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -197,6 +215,7 @@ static int mlxbf3_gpio_probe(struct platform_device *pdev)
 	gc->request = gpiochip_generic_request;
 	gc->free = gpiochip_generic_free;
 	gc->owner = THIS_MODULE;
+	gc->add_pin_ranges = mlxbf3_gpio_add_pin_ranges;
 
 	irq = platform_get_irq(pdev, 0);
 	if (irq >= 0) {
@@ -243,6 +262,7 @@ static struct platform_driver mlxbf3_gpio_driver = {
 };
 module_platform_driver(mlxbf3_gpio_driver);
 
+MODULE_SOFTDEP("pre: pinctrl-mlxbf3");
 MODULE_DESCRIPTION("NVIDIA BlueField-3 GPIO Driver");
 MODULE_AUTHOR("Asmaa Mnebhi <asmaa@nvidia.com>");
 MODULE_LICENSE("Dual BSD/GPL");
-- 
2.30.1

Re: [PATCH v1 2/2] gpio: mlxbf3: Support add_pin_ranges()

[Andy Shevchenko]

On Wed, Aug 16, 2023 at 4:59 PM Asmaa Mnebhi <asmaa@nvidia.com> wrote:
>
> Support add_pin_ranges() so that pinctrl_gpio_request() can be called.
> The GPIO value is not modified when the user runs the "gpioset" tool.
> This is because when gpiochip_generic_request is invoked by the gpio-mlxbf3
> driver, "pin_ranges" is empty so it skips "pinctrl_gpio_request()".
> pinctrl_gpio_request() is essential in the code flow because it changes the
> mux value so that software has control over modifying the GPIO value.
> Adding add_pin_ranges() creates a dependency on the pinctrl-mlxbf3.c driver.

...

> +static int mlxbf3_gpio_add_pin_ranges(struct gpio_chip *chip)
> +{
> +       int ret;
> +       int id = 0;

Redundant assignment.

> +       id = !!(chip->ngpio % MLXBF3_GPIO_MAX_PINS_PER_BLOCK);

Using int as boolean. Seems to me you wanted something different here.

> +       ret = gpiochip_add_pin_range(chip,
> +                       "MLNXBF34:00",
> +                       chip->base,
> +                       id * MLXBF3_GPIO_MAX_PINS_PER_BLOCK,
> +                       chip->ngpio);
> +       if (ret)
> +               return ret;
> +
> +       return 0;

You can return directly:

  return gpiochip_add_pin_range(...);

> +}

-- 
With Best Regards,
Andy Shevchenko