gpio: mmio: Add flag for calling pinctrl back-end

It turns out that with this flag we can switch over an entire
driver to use gpio-mmio instead of a bunch of custom code,
also providing get/set_multiple() to it in the process, so it
seems like a reasonable feature to add.

The generic pin control backend requires us to call the
gpiochip_generic_request(), gpiochip_generic_free(),
pinctrl_gpio_direction_output() and pinctrl_gpio_direction_input()
callbacks, so if the new flag for a pin control back-end
is set, we make sure these functions get called as
expected.

Signed-off-by: Linus Walleij <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bartosz Golaszewski <[e-mail]>

drivers/gpio/gpio-mmio.c

···
 #include <linux/log2.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
+#include <linux/pinctrl/consumer.h>
 #include <linux/platform_device.h>
 #include <linux/property.h>
 #include <linux/slab.h>
···
 		gc->write_reg(gc->reg_clr, clear_mask);
 }
 
+static int bgpio_dir_return(struct gpio_chip *gc, unsigned int gpio, bool dir_out)
+{
+	if (!gc->bgpio_pinctrl)
+		return 0;
+
+	if (dir_out)
+		return pinctrl_gpio_direction_output(gc, gpio);
+	else
+		return pinctrl_gpio_direction_input(gc, gpio);
+}
+
 static int bgpio_simple_dir_in(struct gpio_chip *gc, unsigned int gpio)
 {
-	return 0;
+	return bgpio_dir_return(gc, gpio, false);
 }
 
 static int bgpio_dir_out_err(struct gpio_chip *gc, unsigned int gpio,
···
 {
 	gc->set(gc, gpio, val);
 
-	return 0;
+	return bgpio_dir_return(gc, gpio, true);
 }
 
 static int bgpio_dir_in(struct gpio_chip *gc, unsigned int gpio)
···
 
 	raw_spin_unlock_irqrestore(&gc->bgpio_lock, flags);
 
-	return 0;
+	return bgpio_dir_return(gc, gpio, false);
 }
 
 static int bgpio_get_dir(struct gpio_chip *gc, unsigned int gpio)
···
 {
 	bgpio_dir_out(gc, gpio, val);
 	gc->set(gc, gpio, val);
-	return 0;
+	return bgpio_dir_return(gc, gpio, true);
 }
 
 static int bgpio_dir_out_val_first(struct gpio_chip *gc, unsigned int gpio,
···
 {
 	gc->set(gc, gpio, val);
 	bgpio_dir_out(gc, gpio, val);
-	return 0;
+	return bgpio_dir_return(gc, gpio, true);
 }
 
 static int bgpio_setup_accessors(struct device *dev,
···
 
 static int bgpio_request(struct gpio_chip *chip, unsigned gpio_pin)
 {
-	if (gpio_pin < chip->ngpio)
-		return 0;
+	if (gpio_pin >= chip->ngpio)
+		return -EINVAL;
 
-	return -EINVAL;
+	if (chip->bgpio_pinctrl)
+		return gpiochip_generic_request(chip, gpio_pin);
+
+	return 0;
 }
 
 /**
···
 	ret = bgpio_setup_direction(gc, dirout, dirin, flags);
 	if (ret)
 		return ret;
+
+	if (flags & BGPIOF_PINCTRL_BACKEND) {
+		gc->bgpio_pinctrl = true;
+		/* Currently this callback is only used for pincontrol */
+		gc->free = gpiochip_generic_free;
+	}
 
 	gc->bgpio_data = gc->read_reg(gc->reg_dat);
 	if (gc->set == bgpio_set_set &&

include/linux/gpio/driver.h

···
  * @reg_dir_in: direction in setting register for generic GPIO
  * @bgpio_dir_unreadable: indicates that the direction register(s) cannot
  *	be read and we need to rely on out internal state tracking.
+ * @bgpio_pinctrl: the generic GPIO uses a pin control backend.
  * @bgpio_bits: number of register bits used for a generic GPIO i.e.
  *	<register width> * 8
  * @bgpio_lock: used to lock chip->bgpio_data. Also, this is needed to keep
···
 	void __iomem *reg_dir_out;
 	void __iomem *reg_dir_in;
 	bool bgpio_dir_unreadable;
+	bool bgpio_pinctrl;
 	int bgpio_bits;
 	raw_spinlock_t bgpio_lock;
 	unsigned long bgpio_data;
···
 #define BGPIOF_READ_OUTPUT_REG_SET	BIT(4) /* reg_set stores output value */
 #define BGPIOF_NO_OUTPUT		BIT(5) /* only input */
 #define BGPIOF_NO_SET_ON_INPUT		BIT(6)
+#define BGPIOF_PINCTRL_BACKEND		BIT(7) /* Call pinctrl direction setters */
 
 #ifdef CONFIG_GPIOLIB_IRQCHIP
 int gpiochip_irqchip_add_domain(struct gpio_chip *gc,