[RFC PATCH 2/2] pinctrl: pinconf-generic: Add an overridable way to set bias property

[Konrad Dybcio <konrad.dybcio@linaro.org>]

We came to a point where we sometimes we support a few dozen boards
with a given SoC. Sometimes, we have to take into consideration
configurations which deviate rather significatly from the reference
or most common designs. In the context of pinctrl, this often comes
down to wildly different pin configurations. While pins, function and
drive-strength are easily overridable, the (mostly) boolean properties
associated with setting bias, aren't. This wouldn't be much of a
problem if they didn't differ between boards so often, preventing us
from having a "nice" baseline setup without inevitably having to go
with an ugly /delete-property/.

Introduce logic to handle bias-type, a property which sets a single
boolean type of bias on the pin (more than one type of BIAS_ does not
make sense, anyway) to make it easily overridable.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
---
 drivers/pinctrl/pinconf-generic.c       | 35 ++++++++++++++++++++++---
 include/linux/pinctrl/pinconf-generic.h |  1 +
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/drivers/pinctrl/pinconf-generic.c b/drivers/pinctrl/pinconf-generic.c
index 365c4b0ca465..b99c2a85486e 100644
--- a/drivers/pinctrl/pinconf-generic.c
+++ b/drivers/pinctrl/pinconf-generic.c
@@ -206,11 +206,38 @@ static void parse_dt_cfg(struct device_node *np,
 			 unsigned int count, unsigned long *cfg,
 			 unsigned int *ncfg)
 {
-	int i;
+	int i, ret;
+	u32 val;
+
+	/* Let's assume only one type of bias is used.. as it should be.. */
+	ret = of_property_read_u32(np, "bias-type", &val);
+	if (!ret) {
+		/* Bias properties end at idx PIN_CONFIG_BIAS_PULL_UP */
+		if (ret > PIN_CONFIG_BIAS_PULL_UP) {
+			pr_err("invalid type: %u\n", val);
+			goto generic_parse;
+		}
 
-	for (i = 0; i < count; i++) {
-		u32 val;
-		int ret;
+		pr_debug("found bias type %u\n", val);
+		/*
+		 * Properties between PIN_CONFIG_BIAS_PULL_DOWN and PIN_CONFIG_BIAS_PULL_UP
+		 * have a default value of one, others default to zero.
+		 */
+		cfg[*ncfg] = pinconf_to_config_packed(val, val >= PIN_CONFIG_BIAS_PULL_DOWN);
+		(*ncfg)++;
+
+		/* Start the generic property read loop where bias properties end. */
+		i = PIN_CONFIG_DRIVE_OPEN_DRAIN;
+	} else {
+		/*
+		 * If we don't set bias through bias-type, search for all DT
+		 * properties like nothing ever happened.
+		 */
+generic_parse:
+		i = 0;
+	}
+
+	for (; i < count; i++) {
 		const struct pinconf_generic_params *par = &params[i];
 
 		ret = of_property_read_u32(np, par->property, &val);
diff --git a/include/linux/pinctrl/pinconf-generic.h b/include/linux/pinctrl/pinconf-generic.h
index d74b7a4ea154..bcf68ba1ea46 100644
--- a/include/linux/pinctrl/pinconf-generic.h
+++ b/include/linux/pinctrl/pinconf-generic.h
@@ -117,6 +117,7 @@ struct pinctrl_map;
  *	presented using the packed format.
  */
 enum pin_config_param {
+	/* Keep in sync with dt-bindings/pinctrl/pinconf-generic.h! */
 	PIN_CONFIG_BIAS_BUS_HOLD,
 	PIN_CONFIG_BIAS_DISABLE,
 	PIN_CONFIG_BIAS_HIGH_IMPEDANCE,
-- 
2.39.1