pinctrl: add function to parse generic pinconfig properties from a dt node

pinconf_generic_parse_dt_config() takes a node as input and generates an
array of generic pinconfig values from the properties of this node.

As I couldn't find a mechanism to count the number of properties of a node
the function uses internally an array to accept one of parameter and copies
the real present options to a smaller variable at its end.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/pinctrl-bindings.txt

@@ -126,3 +126,41 @@ device; they may be grandchildren, for example. Whether this is legal, and
 whether there is any interaction between the child and intermediate parent
 nodes, is again defined entirely by the binding for the individual pin
 controller device.
+
+== Using generic pinconfig options ==
+
+Generic pinconfig parameters can be used by defining a separate node containing
+the applicable parameters (and optional values), like:
+
+pcfg_pull_up: pcfg_pull_up {
+	bias-pull-up;
+	drive-strength = <20>;
+};
+
+This node should then be referenced in the appropriate pinctrl node as a phandle
+and parsed in the driver using the pinconf_generic_parse_dt_config function.
+
+Supported configuration parameters are:
+
+bias-disable		- disable any pin bias
+bias-high-impedance	- high impedance mode ("third-state", "floating")
+bias-bus-hold		- latch weakly
+bias-pull-up		- pull up the pin
+bias-pull-down		- pull down the pin
+bias-pull-pin-default	- use pin-default pull state
+drive-push-pull		- drive actively high and low
+drive-open-drain	- drive with open drain
+drive-open-source	- drive with open source
+drive-strength		- sink or source at most X mA
+input-schmitt-enable	- enable schmitt-trigger mode
+input-schmitt-disable	- disable schmitt-trigger mode
+input-schmitt		- run in schmitt-trigger mode with hysteresis X
+input-debounce		- debounce mode with debound time X
+power-source		- select power source X
+slew-rate		- use slew-rate X
+low-power-mode		- low power mode
+output-low		- set the pin to output mode with low level
+output-high		- set the pin to output mode with high level
+
+More in-depth documentation on these parameters can be found in
+<include/linux/pinctrl/pinconfig-generic.h>

drivers/pinctrl/pinconf-generic.c

@@ -21,6 +21,7 @@
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/pinctrl/pinconf.h>
 #include <linux/pinctrl/pinconf-generic.h>
+#include <linux/of.h>
 #include "core.h"
 #include "pinconf.h"
 
@@ -139,3 +140,83 @@ void pinconf_generic_dump_config(struct pinctrl_dev *pctldev,
 }
 EXPORT_SYMBOL_GPL(pinconf_generic_dump_config);
 #endif
+
+#ifdef CONFIG_OF
+struct pinconf_generic_dt_params {
+	const char * const property;
+	enum pin_config_param param;
+	u32 default_value;
+};
+
+static struct pinconf_generic_dt_params dt_params[] = {
+	{ "bias-disable", PIN_CONFIG_BIAS_DISABLE, 0 },
+	{ "bias-high-impedance", PIN_CONFIG_BIAS_HIGH_IMPEDANCE, 0 },
+	{ "bias-bus-hold", PIN_CONFIG_BIAS_BUS_HOLD, 0 },
+	{ "bias-pull-up", PIN_CONFIG_BIAS_PULL_UP, 0 },
+	{ "bias-pull-down", PIN_CONFIG_BIAS_PULL_DOWN, 0 },
+	{ "bias-pull-pin-default", PIN_CONFIG_BIAS_PULL_PIN_DEFAULT, 0 },
+	{ "drive-push-pull", PIN_CONFIG_DRIVE_PUSH_PULL, 0 },
+	{ "drive-open-drain", PIN_CONFIG_DRIVE_OPEN_DRAIN, 0 },
+	{ "drive-open-source", PIN_CONFIG_DRIVE_OPEN_SOURCE, 0 },
+	{ "drive-strength", PIN_CONFIG_DRIVE_STRENGTH, 0 },
+	{ "input-schmitt-enable", PIN_CONFIG_INPUT_SCHMITT_ENABLE, 1 },
+	{ "input-schmitt-disable", PIN_CONFIG_INPUT_SCHMITT_ENABLE, 0 },
+	{ "input-schmitt", PIN_CONFIG_INPUT_SCHMITT, 0 },
+	{ "input-debounce", PIN_CONFIG_INPUT_DEBOUNCE, 0 },
+	{ "power-source", PIN_CONFIG_POWER_SOURCE, 0 },
+	{ "slew-rate", PIN_CONFIG_SLEW_RATE, 0 },
+	{ "low-power-mode", PIN_CONFIG_LOW_POWER_MODE, 0 },
+	{ "output-low", PIN_CONFIG_OUTPUT, 0, },
+	{ "output-high", PIN_CONFIG_OUTPUT, 1, },
+};
+
+/**
+ * pinconf_generic_parse_dt_config()
+ * parse the config properties into generic pinconfig values.
+ * @np: node containing the pinconfig properties
+ * @configs: array with nconfigs entries containing the generic pinconf values
+ * @nconfigs: umber of configurations
+ */
+int pinconf_generic_parse_dt_config(struct device_node *np,
+				    unsigned long **configs,
+				    unsigned int *nconfigs)
+{
+	unsigned long cfg[ARRAY_SIZE(dt_params)];
+	unsigned int ncfg = 0;
+	int ret;
+	int i;
+	u32 val;
+
+	if (!np)
+		return -EINVAL;
+
+	for (i = 0; i < ARRAY_SIZE(dt_params); i++) {
+		struct pinconf_generic_dt_params *par = &dt_params[i];
+		ret = of_property_read_u32(np, par->property, &val);
+
+		/* property not found */
+		if (ret == -EINVAL)
+			continue;
+
+		/* use default value, when no value is specified */
+		if (ret)
+			val = par->default_value;
+
+		pr_debug("found %s with value %u\n", par->property, val);
+		cfg[ncfg] = pinconf_to_config_packed(par->param, val);
+		ncfg++;
+	}
+
+	/*
+	 * Now limit the number of configs to the real number of
+	 * found properties.
+	 */
+	*configs = kzalloc(ncfg * sizeof(unsigned long), GFP_KERNEL);
+	if (!*configs)
+		return -ENOMEM;
+
+	memcpy(*configs, &cfg, ncfg * sizeof(unsigned long));
+	*nconfigs = ncfg;
+	return 0;
+}
+#endif

drivers/pinctrl/pinconf.h

@@ -123,3 +123,9 @@ static inline void pinconf_generic_dump_config(struct pinctrl_dev *pctldev,
 	return;
 }
 #endif
+
+#if defined(CONFIG_GENERIC_PINCONF) && defined(CONFIG_OF)
+int pinconf_generic_parse_dt_config(struct device_node *np,
+				    unsigned long **configs,
+				    unsigned int *nconfigs);
+#endif