[PATCH v2 2/7] gpio: regmap: Add configurable dir/value order

[Sander Vanheule <sander@svanheule.net>]

GPIO chips may not support setting the output value when a pin is
configured as an input, although the current implementation assumes this
is always possible.

Add support for setting pin direction before value. The order defaults
to setting the value first, but this can be reversed by setting the
regmap_config.no_set_on_input flag, similar to the corresponding flag in
the gpio-mmio driver.

Signed-off-by: Sander Vanheule <sander@svanheule.net>
---
 drivers/gpio/gpio-regmap.c  | 20 +++++++++++++++++---
 include/linux/gpio/regmap.h |  3 +++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
index 134cedf151a7..1cdb20f8f8b4 100644
--- a/drivers/gpio/gpio-regmap.c
+++ b/drivers/gpio/gpio-regmap.c
@@ -170,14 +170,25 @@ static int gpio_regmap_direction_input(struct gpio_chip *chip,
 	return gpio_regmap_set_direction(chip, offset, false);
 }
 
-static int gpio_regmap_direction_output(struct gpio_chip *chip,
-					unsigned int offset, int value)
+static int gpio_regmap_dir_out_val_first(struct gpio_chip *chip,
+					 unsigned int offset, int value)
 {
 	gpio_regmap_set(chip, offset, value);
 
 	return gpio_regmap_set_direction(chip, offset, true);
 }
 
+static int gpio_regmap_dir_out_dir_first(struct gpio_chip *chip,
+					 unsigned int offset, int value)
+{
+	int err;
+
+	err = gpio_regmap_set_direction(chip, offset, true);
+	gpio_regmap_set(chip, offset, value);
+
+	return err;
+}
+
 void gpio_regmap_set_drvdata(struct gpio_regmap *gpio, void *data)
 {
 	gpio->driver_data = data;
@@ -277,7 +288,10 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
 	if (gpio->reg_dir_in_base || gpio->reg_dir_out_base) {
 		chip->get_direction = gpio_regmap_get_direction;
 		chip->direction_input = gpio_regmap_direction_input;
-		chip->direction_output = gpio_regmap_direction_output;
+		if (config->no_set_on_input)
+			chip->direction_output = gpio_regmap_dir_out_dir_first;
+		else
+			chip->direction_output = gpio_regmap_dir_out_val_first;
 	}
 
 	ret = gpiochip_add_data(chip, gpio);
diff --git a/include/linux/gpio/regmap.h b/include/linux/gpio/regmap.h
index 334dd928042b..2a732f8f23be 100644
--- a/include/linux/gpio/regmap.h
+++ b/include/linux/gpio/regmap.h
@@ -30,6 +30,8 @@ struct regmap;
  * @reg_dir_out_base:	(Optional) out setting register base address
  * @reg_stride:		(Optional) May be set if the registers (of the
  *			same type, dat, set, etc) are not consecutive.
+ * @no_set_on_input:	Set if output value can only be set when the direction
+ *			is configured as output.
  * @ngpio_per_reg:	Number of GPIOs per register
  * @irq_domain:		(Optional) IRQ domain if the controller is
  *			interrupt-capable
@@ -73,6 +75,7 @@ struct gpio_regmap_config {
 	unsigned int reg_dir_out_base;
 	int reg_stride;
 	int ngpio_per_reg;
+	bool no_set_on_input;
 	struct irq_domain *irq_domain;
 
 	int (*reg_mask_xlate)(struct gpio_regmap *gpio, unsigned int base,
-- 
2.31.1