[PATCH 1/3] gpio: regmap: Support registers with more than one bit per GPIO

[Aidan MacDonald <aidanmacdonald.0x0@xxxxxxxxx>]

Some devices use a multi-bit register field to change the GPIO
input/output direction. Add the ->reg_field_xlate() callback to
support such devices in gpio-regmap.

->reg_field_xlate() builds on ->reg_mask_xlate() by allowing the
driver to return a mask and values to describe a register field.
gpio-regmap will use the mask to isolate the field and compare or
update it using the values to implement GPIO level and direction
get and set ops.

Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@xxxxxxxxx>
---
 drivers/gpio/gpio-regmap.c  | 73 +++++++++++++++++++++----------------
 include/linux/gpio/regmap.h | 14 +++++++
 2 files changed, 56 insertions(+), 31 deletions(-)

diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
index 6383136cbe59..9256b922c654 100644
--- a/drivers/gpio/gpio-regmap.c
+++ b/drivers/gpio/gpio-regmap.c
@@ -27,6 +27,10 @@ struct gpio_regmap {
 	int (*reg_mask_xlate)(struct gpio_regmap *gpio, unsigned int base,
 			      unsigned int offset, unsigned int *reg,
 			      unsigned int *mask);
+	void (*reg_field_xlate)(struct gpio_regmap *gpio,
+				unsigned int base, unsigned int offset,
+				unsigned int *reg, unsigned int *mask,
+				unsigned int *values);
 
 	void *driver_data;
 };
@@ -52,10 +56,22 @@ static int gpio_regmap_simple_xlate(struct gpio_regmap *gpio,
 	return 0;
 }
 
+static void
+gpio_regmap_simple_field_xlate(struct gpio_regmap *gpio,
+			       unsigned int base, unsigned int offset,
+			       unsigned int *reg, unsigned int *mask,
+			       unsigned int *values)
+{
+	gpio->reg_mask_xlate(gpio, base, offset, reg, mask);
+	values[0] = 0;
+	values[1] = *mask;
+}
+
 static int gpio_regmap_get(struct gpio_chip *chip, unsigned int offset)
 {
 	struct gpio_regmap *gpio = gpiochip_get_data(chip);
 	unsigned int base, val, reg, mask;
+	unsigned int values[2];
 	int ret;
 
 	/* we might not have an output register if we are input only */
@@ -64,15 +80,13 @@ static int gpio_regmap_get(struct gpio_chip *chip, unsigned int offset)
 	else
 		base = gpio_regmap_addr(gpio->reg_set_base);
 
-	ret = gpio->reg_mask_xlate(gpio, base, offset, &reg, &mask);
-	if (ret)
-		return ret;
+	gpio->reg_field_xlate(gpio, base, offset, &reg, &mask, values);
 
 	ret = regmap_read(gpio->regmap, reg, &val);
 	if (ret)
 		return ret;
 
-	return !!(val & mask);
+	return (val & mask) == values[1];
 }
 
 static void gpio_regmap_set(struct gpio_chip *chip, unsigned int offset,
@@ -81,12 +95,10 @@ static void gpio_regmap_set(struct gpio_chip *chip, unsigned int offset,
 	struct gpio_regmap *gpio = gpiochip_get_data(chip);
 	unsigned int base = gpio_regmap_addr(gpio->reg_set_base);
 	unsigned int reg, mask;
+	unsigned int values[2];
 
-	gpio->reg_mask_xlate(gpio, base, offset, &reg, &mask);
-	if (val)
-		regmap_update_bits(gpio->regmap, reg, mask, mask);
-	else
-		regmap_update_bits(gpio->regmap, reg, mask, 0);
+	gpio->reg_field_xlate(gpio, base, offset, &reg, &mask, values);
+	regmap_update_bits(gpio->regmap, reg, mask, values[!!val]);
 }
 
 static void gpio_regmap_set_with_clear(struct gpio_chip *chip,
@@ -94,14 +106,15 @@ static void gpio_regmap_set_with_clear(struct gpio_chip *chip,
 {
 	struct gpio_regmap *gpio = gpiochip_get_data(chip);
 	unsigned int base, reg, mask;
+	unsigned int values[2];
 
 	if (val)
 		base = gpio_regmap_addr(gpio->reg_set_base);
 	else
 		base = gpio_regmap_addr(gpio->reg_clr_base);
 
-	gpio->reg_mask_xlate(gpio, base, offset, &reg, &mask);
-	regmap_write(gpio->regmap, reg, mask);
+	gpio->reg_field_xlate(gpio, base, offset, &reg, &mask, values);
+	regmap_update_bits(gpio->regmap, reg, mask, values[1]);
 }
 
 static int gpio_regmap_get_direction(struct gpio_chip *chip,
@@ -109,6 +122,7 @@ static int gpio_regmap_get_direction(struct gpio_chip *chip,
 {
 	struct gpio_regmap *gpio = gpiochip_get_data(chip);
 	unsigned int base, val, reg, mask;
+	unsigned int values[2];
 	int invert, ret;
 
 	if (gpio->reg_dir_out_base) {
@@ -121,47 +135,36 @@ static int gpio_regmap_get_direction(struct gpio_chip *chip,
 		return -EOPNOTSUPP;
 	}
 
-	ret = gpio->reg_mask_xlate(gpio, base, offset, &reg, &mask);
-	if (ret)
-		return ret;
+	gpio->reg_field_xlate(gpio, base, offset, &reg, &mask, values);
 
 	ret = regmap_read(gpio->regmap, reg, &val);
 	if (ret)
 		return ret;
 
-	if (!!(val & mask) ^ invert)
-		return GPIO_LINE_DIRECTION_OUT;
-	else
+	if ((val & mask) == values[invert])
 		return GPIO_LINE_DIRECTION_IN;
+	else
+		return GPIO_LINE_DIRECTION_OUT;
 }
 
 static int gpio_regmap_set_direction(struct gpio_chip *chip,
 				     unsigned int offset, bool output)
 {
 	struct gpio_regmap *gpio = gpiochip_get_data(chip);
-	unsigned int base, val, reg, mask;
-	int invert, ret;
+	unsigned int base, reg, mask;
+	unsigned int values[2];
 
 	if (gpio->reg_dir_out_base) {
 		base = gpio_regmap_addr(gpio->reg_dir_out_base);
-		invert = 0;
 	} else if (gpio->reg_dir_in_base) {
 		base = gpio_regmap_addr(gpio->reg_dir_in_base);
-		invert = 1;
+		output = !output;
 	} else {
 		return -EOPNOTSUPP;
 	}
 
-	ret = gpio->reg_mask_xlate(gpio, base, offset, &reg, &mask);
-	if (ret)
-		return ret;
-
-	if (invert)
-		val = output ? 0 : mask;
-	else
-		val = output ? mask : 0;
-
-	return regmap_update_bits(gpio->regmap, reg, mask, val);
+	gpio->reg_field_xlate(gpio, base, offset, &reg, &mask, values);
+	return regmap_update_bits(gpio->regmap, reg, mask, values[output]);
 }
 
 static int gpio_regmap_direction_input(struct gpio_chip *chip,
@@ -215,6 +218,10 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
 	if (config->reg_dir_out_base && config->reg_dir_in_base)
 		return ERR_PTR(-EINVAL);
 
+	/* only one of these should be provided */
+	if (config->reg_field_xlate && config->reg_mask_xlate)
+		return ERR_PTR(-EINVAL);
+
 	gpio = kzalloc(sizeof(*gpio), GFP_KERNEL);
 	if (!gpio)
 		return ERR_PTR(-ENOMEM);
@@ -225,6 +232,7 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
 	gpio->ngpio_per_reg = config->ngpio_per_reg;
 	gpio->reg_stride = config->reg_stride;
 	gpio->reg_mask_xlate = config->reg_mask_xlate;
+	gpio->reg_field_xlate = config->reg_field_xlate;
 	gpio->reg_dat_base = config->reg_dat_base;
 	gpio->reg_set_base = config->reg_set_base;
 	gpio->reg_clr_base = config->reg_clr_base;
@@ -242,6 +250,9 @@ struct gpio_regmap *gpio_regmap_register(const struct gpio_regmap_config *config
 	if (!gpio->reg_mask_xlate)
 		gpio->reg_mask_xlate = gpio_regmap_simple_xlate;
 
+	if (!gpio->reg_field_xlate)
+		gpio->reg_field_xlate = gpio_regmap_simple_field_xlate;
+
 	chip = &gpio->gpio_chip;
 	chip->parent = config->parent;
 	chip->fwnode = config->fwnode;
diff --git a/include/linux/gpio/regmap.h b/include/linux/gpio/regmap.h
index a9f7b7faf57b..a673dbfe88a3 100644
--- a/include/linux/gpio/regmap.h
+++ b/include/linux/gpio/regmap.h
@@ -37,6 +37,10 @@ struct regmap;
  *			offset to a register/bitmask pair. If not
  *			given the default gpio_regmap_simple_xlate()
  *			is used.
+ * @reg_field_xlate:	(Optional) Translates base address and GPIO offset
+ *			to register, mask, and field values. If not given
+ *			the default gpio_regmap_field_xlate() is used, which
+ *			is implemented in terms of ->reg_mask_xlate.
  * @drvdata:		(Optional) Pointer to driver specific data which is
  *			not used by gpio-remap but is provided "as is" to the
  *			driver callback(s).
@@ -45,6 +49,12 @@ struct regmap;
  * register and mask pair. The base address is one of the given register
  * base addresses in this structure.
  *
+ * ->reg_field_xlate supports chips that have more than one bit per GPIO for
+ * controlling the output level or direction. In addition to the register and
+ * mask it should output field values for low/high level or in/out direction
+ * in ``values[0]`` and ``values[1]``. If ->reg_field_xlate is provided then
+ * it overrides any ->reg_mask_xlate callback.
+ *
  * Although all register base addresses are marked as optional, there are
  * several rules:
  *     1. if you only have @reg_dat_base set, then it is input-only
@@ -81,6 +91,10 @@ struct gpio_regmap_config {
 	int (*reg_mask_xlate)(struct gpio_regmap *gpio, unsigned int base,
 			      unsigned int offset, unsigned int *reg,
 			      unsigned int *mask);
+	void (*reg_field_xlate)(struct gpio_regmap *gpio,
+				unsigned int base, unsigned int offset,
+				unsigned int *reg, unsigned int *mask,
+				unsigned int *values);
 
 	void *drvdata;
 };
-- 
2.35.1