[PATCH 3/3] gpiolib: Add GPIO initialization

[Markus Pargmann]

From: Markus Pargmann <mpa at devmp.org>

This functions adds a way to initialize a GPIO without hogging it.

Signed-off-by: Markus Pargmann <mpa at devmp.org>
---
 Documentation/devicetree/bindings/gpio/gpio.txt | 29 +++++++------
 drivers/gpio/gpiolib-of.c                       |  9 ++++
 drivers/gpio/gpiolib.c                          | 55 ++++++++++++++++++++-----
 drivers/gpio/gpiolib.h                          |  2 +
 4 files changed, 73 insertions(+), 22 deletions(-)

diff --git a/Documentation/devicetree/bindings/gpio/gpio.txt b/Documentation/devicetree/bindings/gpio/gpio.txt
index 5788d5cf1252..55d58983ba43 100644
--- a/Documentation/devicetree/bindings/gpio/gpio.txt
+++ b/Documentation/devicetree/bindings/gpio/gpio.txt
@@ -116,29 +116,34 @@ Every GPIO controller node must contain both an empty "gpio-controller"
 property, and a #gpio-cells integer property, which indicates the number of
 cells in a gpio-specifier.
 
-The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism
-providing automatic GPIO request and configuration as part of the
-gpio-controller's driver probe function.
+The GPIO chip may contain GPIO definitions. These define properties for single
+GPIOs of this controller.
 
-Each GPIO hog definition is represented as a child node of the GPIO controller.
+GPIO hogging is a mechanism providing automatic GPIO request and configuration
+as part of the gpio-controller's driver probe function.
+
+GPIO initialization provides an automatic initialization to known save values.
+Instead of GPIO hogging the GPIO's value and direction can be modified by other
+users after it was initialized.
+
+Each GPIO definition is represented as a child node of the GPIO controller.
 Required properties:
-- gpio-hog:   A property specifying that this child node represent a GPIO hog.
 - gpios:      Store the GPIO information (id, flags, ...). Shall contain the
 	      number of cells specified in its parent node (GPIO controller
 	      node).
-Only one of the following properties scanned in the order shown below.
-This means that when multiple properties are present they will be searched
-in the order presented below and the first match is taken as the intended
-configuration.
+
+Optional properties:
+- line-name:  The GPIO label name. If not present the node name is used.
+ Only one of gpio-hog and gpio-initval may be specified.
+- gpio-hog:   A property specifying that this child node represent a GPIO hog.
+- gpio-initval: This GPIO should be initialized to the specified configuration.
+ Only one of input, output-low and output-high may be specified:
 - input:      A property specifying to set the GPIO direction as input.
 - output-low  A property specifying to set the GPIO direction as output with
 	      the value low.
 - output-high A property specifying to set the GPIO direction as output with
 	      the value high.
 
-Optional properties:
-- line-name:  The GPIO label name. If not present the node name is used.
-
 Example of two SOC GPIO banks defined as gpio-controller nodes:
 
 	qe_pio_a: gpio-controller at 1400 {
diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index f1fe5123da28..ee00c2c63f57 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -234,6 +234,15 @@ static void of_gpiochip_scan_gpios(struct gpio_chip *chip)
 
 			if (gpiod_hog(desc, lflags, dflags))
 				continue;
+		} else if (of_property_read_bool(np, "gpio-initval")) {
+			if (!dflags) {
+				dev_warn(chip->dev, "GPIO line %d (%s): no initialization state specified, bailing out\n",
+					 desc_to_gpio(desc), np->name);
+				continue;
+			}
+
+			if (gpiod_initialize(desc, lflags, dflags))
+				continue;
 		}
 	}
 }
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f1559fa72c36..d7aa27a92e82 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2178,15 +2178,8 @@ struct gpio_desc *__must_check __gpiod_get_index_optional(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(__gpiod_get_index_optional);
 
-/**
- * gpiod_hog - Hog the specified GPIO desc given the provided flags
- * @desc:	gpio whose value will be assigned
- * @lflags:	gpio_lookup_flags - returned from of_find_gpio() or
- *		of_get_gpio_hog()
- * @dflags:	gpiod_flags - optional GPIO initialization flags
- */
-int gpiod_hog(struct gpio_desc *desc, unsigned long lflags,
-	      enum gpiod_flags dflags)
+static int _gpiod_initialize(struct gpio_desc *desc, unsigned long lflags,
+		      enum gpiod_flags dflags)
 {
 	int status;
 	const char *name = desc->name;
@@ -2202,11 +2195,31 @@ int gpiod_hog(struct gpio_desc *desc, unsigned long lflags,
 	status = gpiod_configure_flags(desc, name, lflags, dflags);
 	if (status < 0) {
 		pr_err("setup of hog GPIO %s (chip %s, offset %d) failed\n",
-		       name, gpiod_to_chip(desc)->label, gpio_chip_hwgpio(desc));
+		       name, gpiod_to_chip(desc)->label,
+		       gpio_chip_hwgpio(desc));
 		gpiochip_free_own_desc(desc);
 		return status;
 	}
 
+	return 0;
+}
+
+/**
+ * gpiod_hog - Hog the specified GPIO desc given the provided flags
+ * @desc:	gpio whose value will be assigned
+ * @lflags:	gpio_lookup_flags - returned from of_find_gpio() or
+ *		of_get_gpio_hog()
+ * @dflags:	gpiod_flags - optional GPIO initialization flags
+ */
+int gpiod_hog(struct gpio_desc *desc, unsigned long lflags,
+	      enum gpiod_flags dflags)
+{
+	int ret;
+
+	ret = _gpiod_initialize(desc, lflags, dflags);
+	if (ret)
+		return ret;
+
 	/* Mark GPIO as hogged so it can be identified and removed later */
 	set_bit(FLAG_IS_HOGGED, &desc->flags);
 
@@ -2236,6 +2249,28 @@ static void gpiochip_free_hogs(struct gpio_chip *chip)
 }
 
 /**
+ * gpiod_initialize - Initialize a GPIO with a given value
+ * @desc:	gpio whose value will be assigned
+ * @lflags:	gpio_lookup_flags - returned from of_find_gpio() or
+ *		of_get_gpio_hog()
+ * @dflags:	gpiod_flags - optional GPIO initialization flags
+ *
+ * This is used to initialize GPIOs that were defined in DT
+ */
+int gpiod_initialize(struct gpio_desc *desc, unsigned long lflags,
+		     enum gpiod_flags dflags)
+{
+	int ret;
+
+	ret = _gpiod_initialize(desc, lflags, dflags);
+	if (ret)
+		return ret;
+
+	__gpiod_free(desc);
+	return ret;
+}
+
+/**
  * gpiod_get_array - obtain multiple GPIOs from a multi-index GPIO function
  * @dev:	GPIO consumer, can be NULL for system-global GPIOs
  * @con_id:	function within the GPIO consumer
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 6c2aeff59f86..b6dfa3526e3a 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -99,6 +99,8 @@ int gpiod_request(struct gpio_desc *desc, const char *label);
 void gpiod_free(struct gpio_desc *desc);
 int gpiod_hog(struct gpio_desc *desc, unsigned long lflags,
 	      enum gpiod_flags dflags);
+int gpiod_initialize(struct gpio_desc *desc, unsigned long lflags,
+		     enum gpiod_flags dflags);
 
 /*
  * Return the GPIO number of the passed descriptor relative to its chip
-- 
2.4.6