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 <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

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

···
 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

···
 #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"
 
···
 	}
 }
 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

···
 	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