acpi_device: Add support for writing ACPI SPI descriptors

Add required definitions to describe an ACPI SPI bus and a method to
write the SpiSerialBus() descriptor to the SSDT.

This will be used by device drivers to describe their SPI resources to
the OS.  SPI devices are not currently enumerated in the devicetree but
can be enumerated by device drivers directly.

generic.c:
  void acpi_fill_ssdt_generator(struct device *dev) {
    struct acpi_spi spi = {
      .device_select = dev->path->generic.device.id,
      .device_select_polarity = SPI_POLARITY_LOW,
      .spi_wire_mode = SPI_4_WIRE_MODE,
      .speed = 1000 * 1000; /* 1 mHz */
      .data_bit_length = 8,
      .clock_phase = SPI_CLOCK_PHASE_FIRST,
      .clock_polarity = SPI_POLARITY_LOW,
      .resource = acpi_device_path(dev->bus->dev)
    };
    ...
    acpi_device_write_spi(&spi);
    ...
  }

devicetree.cb:
  device pci 1e.2 on
    chip drivers/spi/generic
      device generic 0 on end
    end
  end

SSDT.dsl:
  SpiSerialBus (0, PolarityLow, FourWireMode, 8, ControllerInitiated,
                1000000, ClockPolarityLow, ClockPhaseFirst,
                "\\_SB.PCI0.SPI0", 0, ResourceConsumer)

Change-Id: I0ef83dc111ac6c19d68872ab64e1e5e3a7756cae
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/14936
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

1 files changed, 72 insertions, 0 deletions

diff --git a/src/arch/x86/acpi_device.c b/src/arch/x86/acpi_device.c
index 3c0230fae2..073b938101 100644
--- a/src/arch/x86/acpi_device.c
+++ b/src/arch/x86/acpi_device.c
@@ -381,3 +381,75 @@ void acpi_device_write_i2c(const struct acpi_i2c *i2c)
 	/* Fill in I2C Descriptor Length */
 	acpi_device_fill_len(desc_length);
 }
+
+/* ACPI 6.1 section 6.4.3.8.2.2 - SpiSerialBus() */
+void acpi_device_write_spi(const struct acpi_spi *spi)
+{
+	void *desc_length, *type_length;
+	uint16_t flags = 0;
+
+	/* Byte 0: Descriptor Type */
+	acpigen_emit_byte(ACPI_DESCRIPTOR_SERIAL_BUS);
+
+	/* Byte 1+2: Length (filled in later) */
+	desc_length = acpi_device_write_zero_len();
+
+	/* Byte 3: Revision ID */
+	acpigen_emit_byte(ACPI_SERIAL_BUS_REVISION_ID);
+
+	/* Byte 4: Resource Source Index is Reserved */
+	acpigen_emit_byte(0);
+
+	/* Byte 5: Serial Bus Type is SPI */
+	acpigen_emit_byte(ACPI_SERIAL_BUS_TYPE_SPI);
+
+	/*
+	 * Byte 6: Flags
+	 *  [7:2]: 0 => Reserved
+	 *    [1]: 1 => ResourceConsumer
+	 *    [0]: 0 => ControllerInitiated
+	 */
+	acpigen_emit_byte(1 << 1);
+
+	/*
+	 * Byte 7-8: Type Specific Flags
+	 *   [15:2]: 0 => Reserved
+	 *      [1]: 0 => ActiveLow, 1 => ActiveHigh
+	 *      [0]: 0 => FourWire, 1 => ThreeWire
+	 */
+	if (spi->wire_mode == SPI_3_WIRE_MODE)
+		flags |= 1 << 0;
+	if (spi->device_select_polarity == SPI_POLARITY_HIGH)
+		flags |= 1 << 1;
+	acpigen_emit_word(flags);
+
+	/* Byte 9: Type Specific Revision ID */
+	acpigen_emit_byte(ACPI_SERIAL_BUS_REVISION_ID);
+
+	/* Byte 10-11: SPI Type Data Length */
+	type_length = acpi_device_write_zero_len();
+
+	/* Byte 12-15: Connection Speed */
+	acpigen_emit_dword(spi->speed);
+
+	/* Byte 16: Data Bit Length */
+	acpigen_emit_byte(spi->data_bit_length);
+
+	/* Byte 17: Clock Phase */
+	acpigen_emit_byte(spi->clock_phase);
+
+	/* Byte 18: Clock Polarity */
+	acpigen_emit_byte(spi->clock_polarity);
+
+	/* Byte 19-20: Device Selection */
+	acpigen_emit_word(spi->device_select);
+
+	/* Fill in Type Data Length */
+	acpi_device_fill_len(type_length);
+
+	/* Byte 21+: ResourceSource String */
+	acpigen_emit_string(spi->resource);
+
+	/* Fill in SPI Descriptor Length */
+	acpi_device_fill_len(desc_length);
+}