acpi_device: Replace polarity with active_low in acpi_gpio for GpioIo

As per ACPI spec, GpioIo does not have any polarity associated with
it. Linux kernel uses `active_low` argument within GPIO _DSD property
to allow BIOS to indicate if the corresponding GPIO should be treated
as active low. Thus, if GPIO has active high polarity or if it does
not have any polarity associated with it, then the `active_low`
argument is supposed to be set to 0.

Having a `polarity` field in acpi_gpio seems confusing because GPIOs
might not always have polarity associated with them. Example, in case
of DMIC-select GPIO where 0 means select DMIC0 and 1 means select
DMIC1, there is no polarity associated with the GPIO. Thus, it would
be clearer for mainboard to use macros without having to specify a
particular polarity. In order to enable mainboards to provide GPIO
information without polarity for GpioIo usage, this change also adds
`ACPI_GPIO_OUTPUT` and `ACPI_GPIO_INPUT` macros.

BUG=b:157603026

Change-Id: I39d2a6ac8f149a74afeb915812fece86c9b9ad93
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42968
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

1 files changed, 21 insertions, 20 deletions

diff --git a/src/include/acpi/acpi_device.h b/src/include/acpi/acpi_device.h
index e01b6fd027..6287ba1672 100644
--- a/src/include/acpi/acpi_device.h
+++ b/src/include/acpi/acpi_device.h
@@ -158,11 +158,6 @@ enum acpi_gpio_io_restrict {
 	ACPI_GPIO_IO_RESTRICT_PRESERVE
 };
 
-enum acpi_gpio_polarity {
-	ACPI_GPIO_ACTIVE_HIGH = 0,
-	ACPI_GPIO_ACTIVE_LOW = 1,
-};
-
 #define ACPI_GPIO_REVISION_ID		1
 #define ACPI_GPIO_MAX_PINS		8
 
@@ -182,37 +177,43 @@ struct acpi_gpio {
 	uint16_t output_drive_strength;		/* 1/100 mA */
 	int io_shared;
 	enum acpi_gpio_io_restrict io_restrict;
-	enum acpi_gpio_polarity polarity;
+	/*
+	 * As per ACPI spec, GpioIo does not have any polarity associated with it. Linux kernel
+	 * uses `active_low` argument within GPIO _DSD property to allow BIOS to indicate if the
+	 * corresponding GPIO should be treated as active low. Thus, if the GPIO has active high
+	 * polarity or if it does not have any polarity, then the `active_low` argument is
+	 * supposed to be set to 0.
+	 *
+	 * Reference:
+	 * https://www.kernel.org/doc/html/latest/firmware-guide/acpi/gpio-properties.html
+	 */
+	bool active_low;
 };
 
 /* GpioIo-related macros */
-#define ACPI_GPIO_CFG(_gpio, _io_restrict, _polarity) { \
+#define ACPI_GPIO_CFG(_gpio, _io_restrict, _active_low) { \
 	.type = ACPI_GPIO_TYPE_IO, \
 	.pull = ACPI_GPIO_PULL_DEFAULT, \
 	.io_restrict = _io_restrict, \
-	.polarity = _polarity,     \
+	.active_low = _active_low, \
 	.pin_count = 1, \
 	.pins = { (_gpio) } }
 
 /* Basic output GPIO with default pull settings */
-#define ACPI_GPIO_OUTPUT_CFG(gpio, polarity) \
-		ACPI_GPIO_CFG(gpio, ACPI_GPIO_IO_RESTRICT_OUTPUT, polarity)
+#define ACPI_GPIO_OUTPUT_CFG(gpio, active_low) \
+		ACPI_GPIO_CFG(gpio, ACPI_GPIO_IO_RESTRICT_OUTPUT, active_low)
 
-#define ACPI_GPIO_OUTPUT_ACTIVE_HIGH(gpio) \
-		ACPI_GPIO_OUTPUT_CFG(gpio, ACPI_GPIO_ACTIVE_HIGH)
-
-#define ACPI_GPIO_OUTPUT_ACTIVE_LOW(gpio) \
-		ACPI_GPIO_OUTPUT_CFG(gpio, ACPI_GPIO_ACTIVE_LOW)
+#define ACPI_GPIO_OUTPUT(gpio)			ACPI_GPIO_OUTPUT_CFG(gpio, 0)
+#define ACPI_GPIO_OUTPUT_ACTIVE_HIGH(gpio)	ACPI_GPIO_OUTPUT_CFG(gpio, 0)
+#define ACPI_GPIO_OUTPUT_ACTIVE_LOW(gpio)	ACPI_GPIO_OUTPUT_CFG(gpio, 1)
 
 /* Basic input GPIO with default pull settings */
 #define ACPI_GPIO_INPUT_CFG(gpio, polarity) \
 		ACPI_GPIO_CFG(gpio, ACPI_GPIO_IO_RESTRICT_INPUT, polarity)
 
-#define ACPI_GPIO_INPUT_ACTIVE_HIGH(gpio) \
-		ACPI_GPIO_INPUT_CFG(gpio, ACPI_GPIO_ACTIVE_HIGH)
-
-#define ACPI_GPIO_INPUT_ACTIVE_LOW(gpio) \
-		ACPI_GPIO_INPUT_CFG(gpio, ACPI_GPIO_ACTIVE_LOW)
+#define ACPI_GPIO_INPUT(gpio)			ACPI_GPIO_INPUT_CFG(gpio, 0)
+#define ACPI_GPIO_INPUT_ACTIVE_HIGH(gpio)	ACPI_GPIO_INPUT_CFG(gpio, 0)
+#define ACPI_GPIO_INPUT_ACTIVE_LOW(gpio)	ACPI_GPIO_INPUT_CFG(gpio, 1)
 
 /* GpioInt-related macros */
 #define ACPI_GPIO_IRQ_CFG(_gpio, _mode, _polarity, _wake) { \