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>

src/arch/x86/Makefile.inc

@@ -350,6 +350,7 @@ ramstage-$(CONFIG_GENERATE_PIRQ_TABLE) += pirq_routing.c
 ramstage-$(CONFIG_HAVE_ACPI_TABLES) += acpi.c
 ramstage-$(CONFIG_GENERATE_SMBIOS_TABLES) += smbios.c
 ramstage-$(CONFIG_HAVE_ACPI_TABLES) += acpigen.c
+ramstage-$(CONFIG_HAVE_ACPI_TABLES) += acpi_device.c
 ramstage-$(CONFIG_HAVE_ACPI_RESUME) += wakeup.S
 
 ramstage-y += c_start.S

src/arch/x86/acpi_device.c

@@ -0,0 +1,111 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2016 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <string.h>
+#include <arch/acpi.h>
+#include <arch/acpi_device.h>
+#include <arch/acpigen.h>
+#include <device/device.h>
+#include <device/path.h>
+
+/* Locate and return the ACPI name for this device */
+const char *acpi_device_name(struct device *dev)
+{
+	if (!dev)
+		return NULL;
+
+	/* Check for device specific handler */
+	if (dev->ops->acpi_name)
+		return dev->ops->acpi_name(dev);
+
+	/* Check parent device in case it has a global handler */
+	if (dev->bus && dev->bus->dev->ops->acpi_name)
+		return dev->bus->dev->ops->acpi_name(dev);
+
+	return NULL;
+}
+
+/* Recursive function to find the root device and print a path from there */
+static size_t acpi_device_path_fill(struct device *dev, char *buf,
+				    size_t buf_len, size_t cur)
+{
+	const char *name = acpi_device_name(dev);
+	size_t next = 0;
+
+	/*
+	 * Make sure this name segment will fit, including the path segment
+	 * separator and possible NUL terminator if this is the last segment.
+	 */
+	if (!dev || !name || (cur + strlen(name) + 2) > buf_len)
+		return cur;
+
+	/* Walk up the tree to the root device */
+	if (dev->path.type != DEVICE_PATH_ROOT && dev->bus && dev->bus->dev)
+		next = acpi_device_path_fill(dev->bus->dev, buf, buf_len, cur);
+
+	/* Fill in the path from the root device */
+	next += snprintf(buf + next, buf_len - next, "%s%s",
+			 dev->path.type == DEVICE_PATH_ROOT ? "" : ".", name);
+
+	return next;
+}
+
+/*
+ * Warning: just as with dev_path() this uses a static buffer
+ * so should not be called mulitple times in one statement
+ */
+const char *acpi_device_path(struct device *dev)
+{
+	static char buf[DEVICE_PATH_MAX] = {};
+
+	if (!dev)
+		return NULL;
+
+	if (acpi_device_path_fill(dev, buf, sizeof(buf), 0) <= 0)
+		return NULL;
+
+	return buf;
+}
+
+/* Return the path of the parent device as the ACPI Scope for this device */
+const char *acpi_device_scope(struct device *dev)
+{
+	if (!dev || !dev->bus || !dev->bus->dev)
+		return NULL;
+
+	return acpi_device_path(dev->bus->dev);
+}
+
+/* Concatentate the device path and provided name suffix */
+const char *acpi_device_path_join(struct device *dev, const char *name)
+{
+	static char buf[DEVICE_PATH_MAX] = {};
+	size_t len;
+
+	if (!dev)
+		return NULL;
+
+	/* Build the path of this device */
+	len = acpi_device_path_fill(dev, buf, sizeof(buf), 0);
+	if (len <= 0)
+		return NULL;
+
+	/* Ensure there is room for the added name, separator, and NUL */
+	if ((len + strlen(name) + 2) > sizeof(buf))
+		return NULL;
+	snprintf(buf + len, sizeof(buf) - len, ".%s", name);
+
+	return buf;
+}

src/arch/x86/include/arch/acpi_device.h

@@ -0,0 +1,25 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2016 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef __ACPI_DEVICE_H
+#define __ACPI_DEVICE_H
+
+struct device;
+const char *acpi_device_name(struct device *dev);
+const char *acpi_device_path(struct device *dev);
+const char *acpi_device_scope(struct device *dev);
+const char *acpi_device_path_join(struct device *dev, const char *name);
+
+#endif

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
 };

src/include/device/device.h

@@ -59,6 +59,7 @@ struct device_operations {
 	unsigned long (*write_acpi_tables)(device_t dev, unsigned long start,  struct acpi_rsdp *rsdp);
 	void (*acpi_fill_ssdt_generator)(device_t dev);
 	void (*acpi_inject_dsdt_generator)(device_t dev);
+	const char *(*acpi_name)(device_t dev);
 #endif
 	const struct pci_operations *ops_pci;
 	const struct smbus_bus_operations *ops_smbus_bus;