device: Add an ACPI device name and path concept to devices

Add a function to "struct device_operations" to return the ACPI name
for the device, and helper functions to find this name (either from
the device or its parent) and to build a fully qualified ACPI path
from the root device.

This addition will allow device drivers to generate their ACPI AML in
the SSDT at boot, with customization supplied by devicetree.cb,
instead of needing custom DSDT ASL for every mainboard.

The root device acpi_name is defined as "\\_SB" and is used to start
the path when building a fully qualified name.

This requires SOC support to provide handlers for returning the ACPI
name for devices that it owns, and those names must match the objects
declared in the DSDT.  The handler can be done either in each device
driver or with a global handler for the entire SOC.

Simplified example of how this can be used for an i2c device declared
in devicetree.cb with:

  chip soc/intel/skylake          # "\_SB" (from root device)
    device domain 0 on            # "PCI0"
      device pci 19.2 on          # "I2C4"
        chip drivers/i2c/test0
          device i2c 1a.0 on end  # "TST0"
        end
      end
    end
  end

And basic SSDT generating code in the device driver:

  acpigen_write_scope(acpi_device_scope(dev));
  acpigen_write_device(acpi_device_name(dev));
  acpigen_write_string("_HID", "TEST0000");
  acpigen_write_byte("_UID", 0);
  acpigen_pop_len(); /* device */
  acpigen_pop_len(); /* scope */

Will produce this ACPI code:

  Scope (\_SB.PCI0.I2C4) {
    Device (TST0) {
      Name (_HID, "TEST0000")
      Name (_UID, 0)
    }
  }

Change-Id: Ie149595aeab96266fa5f006e7934339f0119ac54
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/14840
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/device/root_device.c b/src/device/root_device.c
index 7ff10ae844..ed1f7d7bfc 100644
--- a/src/device/root_device.c
+++ b/src/device/root_device.c
@@ -130,6 +130,13 @@ static void root_dev_reset(struct bus *bus)
 	hard_reset();
 }
 
+#if IS_ENABLED(CONFIG_HAVE_ACPI_TABLES)
+static const char *root_dev_acpi_name(struct device *dev)
+{
+	return "\\_SB";
+}
+#endif
+
 /**
  * Default device operation for root device.
  *
@@ -144,4 +151,7 @@ struct device_operations default_dev_ops_root = {
 	.init             = DEVICE_NOOP,
 	.scan_bus         = root_dev_scan_bus,
 	.reset_bus        = root_dev_reset,
+#if IS_ENABLED(CONFIG_HAVE_ACPI_TABLES)
+	.acpi_name        = root_dev_acpi_name,
+#endif
 };