On devices with a UCSI PPM in the EC, check for cros_ec_ucsi to be
defined in the OF device tree or an ACPI node. If it is defined by
either OF or ACPI, it does not need to be added as a subdevice of
cros_ec_dev.

Signed-off-by: Jameson Thies <jthies@google.com>
---
 drivers/mfd/cros_ec_dev.c | 40 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 5 deletions(-)

diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
index dc80a272726b..b0523f6541d2 100644
--- a/drivers/mfd/cros_ec_dev.c
+++ b/drivers/mfd/cros_ec_dev.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2014 Google, Inc.
  */
 
+#include <linux/acpi.h>
 #include <linux/dmi.h>
 #include <linux/kconfig.h>
 #include <linux/mfd/core.h>
@@ -131,11 +132,6 @@ static const struct cros_feature_to_cells cros_subdevices[] = {
 		.mfd_cells	= cros_ec_rtc_cells,
 		.num_cells	= ARRAY_SIZE(cros_ec_rtc_cells),
 	},
-	{
-		.id		= EC_FEATURE_UCSI_PPM,
-		.mfd_cells	= cros_ec_ucsi_cells,
-		.num_cells	= ARRAY_SIZE(cros_ec_ucsi_cells),
-	},
 	{
 		.id		= EC_FEATURE_HANG_DETECT,
 		.mfd_cells	= cros_ec_wdt_cells,
@@ -177,6 +173,16 @@ static const struct mfd_cell cros_ec_vbc_cells[] = {
 	{ .name = "cros-ec-vbc", }
 };
 
+static int ucsi_acpi_match(struct device *dev, const void *data)
+{
+	struct acpi_device_id ucsi_acpi_device_ids[] = {
+		{ "GOOG0021", 0 },
+		{"", 0},
+	};
+	return !!acpi_match_device(ucsi_acpi_device_ids, dev);
+}
+
+
 static void cros_ec_class_release(struct device *dev)
 {
 	kfree(to_cros_ec_dev(dev));
@@ -264,6 +270,30 @@ static int ec_device_probe(struct platform_device *pdev)
 		}
 	}
 
+	/*
+	 * FW nodes can load cros_ec_ucsi, but early PDC devices did not define
+	 * the required nodes. On PDC systems without FW nodes for cros_ec_ucsi,
+	 * the driver should be added as an mfd subdevice.
+	 */
+	if (cros_ec_check_features(ec, EC_FEATURE_USB_PD) &&
+	    cros_ec_check_features(ec, EC_FEATURE_UCSI_PPM)) {
+		struct device *acpi_dev = device_find_child(ec->ec_dev->dev,
+							    NULL,
+							    ucsi_acpi_match);
+
+		if (!!acpi_dev) {
+			put_device(acpi_dev);
+		} else if (!of_find_compatible_node(NULL, NULL,
+						    "google,cros-ec-ucsi")) {
+			retval = mfd_add_hotplug_devices(
+				ec->dev, cros_ec_ucsi_cells,
+				ARRAY_SIZE(cros_ec_ucsi_cells));
+			if (retval)
+				dev_warn(ec->dev,
+				    "failed to add cros_ec_ucsi: %d\n", retval);
+		}
+	}
+
 	/*
 	 * UCSI provides power supply information so we don't need to separately
 	 * load the cros_usbpd_charger driver.
-- 
2.51.0.570.gb178f27e6d-goog