pinctrl: sprd: Add pin high impedance mode support

For Spreadtrum pin controller, it will be the high impedance
mode if disable input and output mode for a pin. Thus add
PIN_CONFIG_BIAS_HIGH_IMPEDANCE configuration to support it.

Signed-off-by: Linhua Xu <linhua.xu@unisoc.com>
Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Link: https://lore.kernel.org/r/3bdac4c2673b54c940e511f3fa569ee33b87b8d5.1585124562.git.baolin.wang7@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/sprd/pinctrl-sprd.c

@@ -467,6 +467,12 @@ static int sprd_pinconf_get(struct pinctrl_dev *pctldev, unsigned int pin_id,
 		case PIN_CONFIG_OUTPUT_ENABLE:
 			arg = reg & SLEEP_OUTPUT_MASK;
 			break;
+		case PIN_CONFIG_BIAS_HIGH_IMPEDANCE:
+			if ((reg & SLEEP_OUTPUT) || (reg & SLEEP_INPUT))
+				return -EINVAL;
+
+			arg = 1;
+			break;
 		case PIN_CONFIG_DRIVE_STRENGTH:
 			arg = (reg >> DRIVE_STRENGTH_SHIFT) &
 				DRIVE_STRENGTH_MASK;
@@ -646,6 +652,12 @@ static int sprd_pinconf_set(struct pinctrl_dev *pctldev, unsigned int pin_id,
 					shift = SLEEP_OUTPUT_SHIFT;
 				}
 				break;
+			case PIN_CONFIG_BIAS_HIGH_IMPEDANCE:
+				if (is_sleep_config == true) {
+					val = shift = 0;
+					mask = SLEEP_OUTPUT | SLEEP_INPUT;
+				}
+				break;
 			case PIN_CONFIG_DRIVE_STRENGTH:
 				if (arg < 2 || arg > 60)
 					return -EINVAL;