acpi_device: Add support for writing ACPI GPIO descriptors

Add definitions to describe GPIOs in generated ACPI objects and a
method to write a GpioIo() or GpioInt() descriptor to the SSDT.

ACPI GPIOs have many possible configuration options and a structure
is created to describe it accurately in ACPI terms.  There are many
shared descriptor fields between GpioIo() and GpioInt() so the same
function can write both types.

GpioInt shares many properties with ACPI Interrupts and the same types
are re-used here where possible.  One addition is that GpioInt can be
configured to trigger on both low and high edge transitions.

One descriptor can describe multiple GPIO pins (limited to 8 in this
implementation) that all share configuration and controller and are
used by the same device scope.

Accurately referring to the GPIO controller that this pin is connected
to requires the SoC/board to implement a function handler for
acpi_gpio_path(), or for the caller to provide this directly as a
string in the acpi_gpio->reference variable.

This will get used by device drivers to describe their resources in
the SSDT.  Here is a sample for a Maxim 98357A I2S codec which has a
GPIO for power and channel selection called "sdmode".

chip.h:
  struct drivers_generic_max98357a_config {
    struct acpi_gpio sdmode_gpio;
  };

max98357a.c:
  void acpi_fill_ssdt_generator(struct device *dev) {
    struct drivers_generic_max98357a_config *config = dev->chip_info;
    ...
    acpi_device_write_gpio(&config->sdmode_gpio);
    ...
  }

devicetree.cb:
  device pci 1f.3 on
    chip drivers/generic/max98357a
      register "sdmode_gpio" = "ACPI_GPIO_OUTPUT(GPP_C5)"
      device generic 0 on end
    end
  end

SSDT.dsl:
  GpioIo (Exclusive, PullDefault, 0, 0, IoRestrictionOutputOnly,
          "\\_SB.PCI0.GPIO", 0, ResourceConsumer, ,) { 53 }

Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Change-Id: Ibf5bab9c4bf6f21252373fb013e78f872550b167
Reviewed-on: https://review.coreboot.org/14934
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

1 files changed, 139 insertions, 0 deletions

diff --git a/src/arch/x86/acpi_device.c b/src/arch/x86/acpi_device.c
index b607834349..610b922b34 100644
--- a/src/arch/x86/acpi_device.c
+++ b/src/arch/x86/acpi_device.c
@@ -19,6 +19,9 @@
 #include <arch/acpigen.h>
 #include <device/device.h>
 #include <device/path.h>
+#if IS_ENABLED(CONFIG_GENERIC_GPIO_LIB)
+#include <gpio.h>
+#endif
 
 /* Write empty word value and return pointer to it */
 static void *acpi_device_write_zero_len(void)
@@ -184,3 +187,139 @@ void acpi_device_write_interrupt(const struct acpi_irq *irq)
 	/* Fill in Descriptor Length (account for len word) */
 	acpi_device_fill_len(desc_length);
 }
+
+/* ACPI 6.1 section 6.4.3.8.1 - GPIO Interrupt or I/O */
+void acpi_device_write_gpio(const struct acpi_gpio *gpio)
+{
+	void *start, *desc_length;
+	void *pin_table_offset, *vendor_data_offset, *resource_offset;
+	uint16_t flags = 0;
+	int pin;
+
+	if (!gpio || gpio->type > ACPI_GPIO_TYPE_IO)
+		return;
+
+	start = acpigen_get_current();
+
+	/* Byte 0: Descriptor Type */
+	acpigen_emit_byte(ACPI_DESCRIPTOR_GPIO);
+
+	/* Byte 1-2: Length (fill in later) */
+	desc_length = acpi_device_write_zero_len();
+
+	/* Byte 3: Revision ID */
+	acpigen_emit_byte(ACPI_GPIO_REVISION_ID);
+
+	/* Byte 4: GpioIo or GpioInt */
+	acpigen_emit_byte(gpio->type);
+
+	/*
+	 * Byte 5-6: General Flags
+	 *   [15:1]: 0 => Reserved
+	 *      [0]: 1 => ResourceConsumer
+	 */
+	acpigen_emit_word(1 << 0);
+
+	switch (gpio->type) {
+	case ACPI_GPIO_TYPE_INTERRUPT:
+		/*
+		 * Byte 7-8: GPIO Interrupt Flags
+		 *   [15:5]: 0 => Reserved
+		 *      [4]: Wake     (0=NO_WAKE   1=WAKE)
+		 *      [3]: Sharing  (0=EXCLUSIVE 1=SHARED)
+		 *    [2:1]: Polarity (0=HIGH      1=LOW     2=BOTH)
+		 *      [0]: Mode     (0=LEVEL     1=EDGE)
+		 */
+		if (gpio->irq.mode == IRQ_EDGE_TRIGGERED)
+			flags |= 1 << 0;
+		if (gpio->irq.shared == IRQ_SHARED)
+			flags |= 1 << 3;
+		if (gpio->irq.wake == IRQ_WAKE)
+			flags |= 1 << 4;
+
+		switch (gpio->irq.polarity) {
+		case IRQ_ACTIVE_HIGH:
+			flags |= 0 << 1;
+			break;
+		case IRQ_ACTIVE_LOW:
+			flags |= 1 << 1;
+			break;
+		case IRQ_ACTIVE_BOTH:
+			flags |= 2 << 1;
+			break;
+		}
+		break;
+
+	case ACPI_GPIO_TYPE_IO:
+		/*
+		 * Byte 7-8: GPIO IO Flags
+		 *   [15:4]: 0 => Reserved
+		 *      [3]: Sharing  (0=EXCLUSIVE 1=SHARED)
+		 *      [2]: 0 => Reserved
+		 *    [1:0]: IO Restriction
+		 *           0 => IoRestrictionNone
+		 *           1 => IoRestrictionInputOnly
+		 *           2 => IoRestrictionOutputOnly
+		 *           3 => IoRestrictionNoneAndPreserve
+		 */
+		flags |= gpio->io_restrict & 3;
+		if (gpio->io_shared)
+			flags |= 1 << 3;
+		break;
+	}
+	acpigen_emit_word(flags);
+
+	/*
+	 * Byte 9: Pin Configuration
+	 *  0x01 => Default (no configuration applied)
+	 *  0x02 => Pull-up
+	 *  0x03 => Pull-down
+	 *  0x04-0x7F => Reserved
+	 *  0x80-0xff => Vendor defined
+	 */
+	acpigen_emit_byte(gpio->pull);
+
+	/* Byte 10-11: Output Drive Strength in 1/100 mA */
+	acpigen_emit_word(gpio->output_drive_strength);
+
+	/* Byte 12-13: Debounce Timeout in 1/100 ms */
+	acpigen_emit_word(gpio->interrupt_debounce_timeout);
+
+	/* Byte 14-15: Pin Table Offset, relative to start */
+	pin_table_offset = acpi_device_write_zero_len();
+
+	/* Byte 16: Reserved */
+	acpigen_emit_byte(0);
+
+	/* Byte 17-18: Resource Source Name Offset, relative to start */
+	resource_offset = acpi_device_write_zero_len();
+
+	/* Byte 19-20: Vendor Data Offset, relative to start */
+	vendor_data_offset = acpi_device_write_zero_len();
+
+	/* Byte 21-22: Vendor Data Length */
+	acpigen_emit_word(0);
+
+	/* Fill in Pin Table Offset */
+	acpi_device_fill_from_len(pin_table_offset, start);
+
+	/* Pin Table, one word for each pin */
+	for (pin = 0; pin < gpio->pin_count; pin++)
+		acpigen_emit_word(gpio->pins[pin]);
+
+	/* Fill in Resource Source Name Offset */
+	acpi_device_fill_from_len(resource_offset, start);
+
+	/* Resource Source Name String */
+#if IS_ENABLED(CONFIG_GENERIC_GPIO_LIB)
+	acpigen_emit_string(gpio->resource ? : gpio_acpi_path(gpio->pins[0]));
+#else
+	acpigen_emit_string(gpio->resource);
+#endif
+
+	/* Fill in Vendor Data Offset */
+	acpi_device_fill_from_len(vendor_data_offset, start);
+
+	/* Fill in GPIO Descriptor Length (account for len word) */
+	acpi_device_fill_len(desc_length);
+}