gpio: regmap: add the .fixed_direction_output configuration parameter

There are GPIO controllers such as the one present in the LX2160ARDB
QIXIS FPGA which have fixed-direction input and output GPIO lines mixed
together in a single register. This cannot be modeled using the
gpio-regmap as-is since there is no way to present the true direction of
a GPIO line.

In order to make this use case possible, add a new configuration
parameter - fixed_direction_output - into the gpio_regmap_config
structure. This will enable user drivers to provide a bitmap that
represents the fixed direction of the GPIO lines.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Michael Walle <mwalle@kernel.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

drivers/gpio/gpio-regmap.c

@@ -31,6 +31,7 @@ struct gpio_regmap {
 	unsigned int reg_clr_base;
 	unsigned int reg_dir_in_base;
 	unsigned int reg_dir_out_base;
+	unsigned long *fixed_direction_output;
 
 #ifdef CONFIG_REGMAP_IRQ
 	int regmap_irq_line;
@@ -134,6 +135,13 @@ static int gpio_regmap_get_direction(struct gpio_chip *chip,
 	unsigned int base, val, reg, mask;
 	int invert, ret;
 
+	if (gpio->fixed_direction_output) {
+		if (test_bit(offset, gpio->fixed_direction_output))
+			return GPIO_LINE_DIRECTION_OUT;
+		else
+			return GPIO_LINE_DIRECTION_IN;
+	}
+
 	if (gpio->reg_dat_base && !gpio->reg_set_base)
 		return GPIO_LINE_DIRECTION_IN;
 	if (gpio->reg_set_base && !gpio->reg_dat_base)
@@ -284,6 +292,17 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
 			goto err_free_gpio;
 	}
 
+	if (config->fixed_direction_output) {
+		gpio->fixed_direction_output = bitmap_alloc(chip->ngpio,
+							    GFP_KERNEL);
+		if (!gpio->fixed_direction_output) {
+			ret = -ENOMEM;
+			goto err_free_gpio;
+		}
+		bitmap_copy(gpio->fixed_direction_output,
+			    config->fixed_direction_output, chip->ngpio);
+	}
+
 	/* if not set, assume there is only one register */
 	gpio->ngpio_per_reg = config->ngpio_per_reg;
 	if (!gpio->ngpio_per_reg)
@@ -300,7 +319,7 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
 
 	ret = gpiochip_add_data(chip, gpio);
 	if (ret < 0)
-		goto err_free_gpio;
+		goto err_free_bitmap;
 
 #ifdef CONFIG_REGMAP_IRQ
 	if (config->regmap_irq_chip) {
@@ -309,7 +328,7 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
 						 config->regmap_irq_line, config->regmap_irq_flags,
 						 0, config->regmap_irq_chip, &gpio->irq_chip_data);
 		if (ret)
-			goto err_free_gpio;
+			goto err_free_bitmap;
 
 		irq_domain = regmap_irq_get_domain(gpio->irq_chip_data);
 	} else
@@ -326,6 +345,8 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
 
 err_remove_gpiochip:
 	gpiochip_remove(chip);
+err_free_bitmap:
+	bitmap_free(gpio->fixed_direction_output);
 err_free_gpio:
 	kfree(gpio);
 	return ERR_PTR(ret);
@@ -344,6 +365,7 @@ void gpio_regmap_unregister(struct gpio_regmap *gpio)
 #endif
 
 	gpiochip_remove(&gpio->gpio_chip);
+	bitmap_free(gpio->fixed_direction_output);
 	kfree(gpio);
 }
 EXPORT_SYMBOL_GPL(gpio_regmap_unregister);

include/linux/gpio/regmap.h

@@ -38,6 +38,10 @@ struct regmap;
  *			offset to a register/bitmask pair. If not
  *			given the default gpio_regmap_simple_xlate()
  *			is used.
+ * @fixed_direction_output:
+ *			(Optional) Bitmap representing the fixed direction of
+ *			the GPIO lines. Useful when there are GPIO lines with a
+ *			fixed direction mixed together in the same register.
  * @drvdata:		(Optional) Pointer to driver specific data which is
  *			not used by gpio-remap but is provided "as is" to the
  *			driver callback(s).
@@ -85,6 +89,7 @@ struct gpio_regmap_config {
 	int reg_stride;
 	int ngpio_per_reg;
 	struct irq_domain *irq_domain;
+	unsigned long *fixed_direction_output;
 
 #ifdef CONFIG_REGMAP_IRQ
 	struct regmap_irq_chip *regmap_irq_chip;