pinctrl-tegra: Add config property GPIO mode

The SFIO/GPIO select bit is a crucial part of Tegra's pin multiplexing
system:
- When set to 1, the pin operates in SFIO mode, controlled by the
  pin's assigned special function.
- When set to 0, the pin operates as a general-purpose GPIO.

This SFIO/GPIO select bit that is set for a given pin is not displayed,
adding the support to retrieve this information from the
pinmux set for each pin.

Signed-off-by: Prathamesh Shete <pshete@nvidia.com>
Link: https://lore.kernel.org/20241217153249.5712-1-pshete@nvidia.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/tegra/pinctrl-tegra.c

@@ -96,6 +96,7 @@ static const struct cfg_param {
 	{"nvidia,slew-rate-falling",	TEGRA_PINCONF_PARAM_SLEW_RATE_FALLING},
 	{"nvidia,slew-rate-rising",	TEGRA_PINCONF_PARAM_SLEW_RATE_RISING},
 	{"nvidia,drive-type",		TEGRA_PINCONF_PARAM_DRIVE_TYPE},
+	{"nvidia,gpio-mode",		TEGRA_PINCONF_PARAM_GPIO_MODE},
 };
 
 static int tegra_pinctrl_dt_subnode_to_map(struct pinctrl_dev *pctldev,
@@ -468,6 +469,16 @@ static int tegra_pinconf_reg(struct tegra_pmx *pmx,
 		*bit = g->drvtype_bit;
 		*width = 2;
 		break;
+	case TEGRA_PINCONF_PARAM_GPIO_MODE:
+		if (pmx->soc->sfsel_in_mux) {
+			*bank = g->mux_bank;
+			*reg = g->mux_reg;
+			*bit = g->sfsel_bit;
+			*width = 1;
+		} else {
+			*reg = -EINVAL;
+		}
+		break;
 	default:
 		dev_err(pmx->dev, "Invalid config param %04x\n", param);
 		return -ENOTSUPP;

drivers/pinctrl/tegra/pinctrl-tegra.h

@@ -54,6 +54,8 @@ enum tegra_pinconf_param {
 	TEGRA_PINCONF_PARAM_SLEW_RATE_RISING,
 	/* argument: Integer, range is HW-dependant */
 	TEGRA_PINCONF_PARAM_DRIVE_TYPE,
+	/* argument: Boolean */
+	TEGRA_PINCONF_PARAM_GPIO_MODE,
 };
 
 enum tegra_pinconf_pull {