[PATCH v6 2/4] soundwire: core: add device tree support for slave devices

[Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>]

This patch adds support to parsing device tree based
SoundWire slave devices.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
---
 drivers/soundwire/bus.c   |  2 ++
 drivers/soundwire/bus.h   |  1 +
 drivers/soundwire/slave.c | 52 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index 728db3ebad6e..d83d89b3b15a 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -79,6 +79,8 @@ int sdw_add_bus_master(struct sdw_bus *bus)
 	 */
 	if (IS_ENABLED(CONFIG_ACPI) && ACPI_HANDLE(bus->dev))
 		ret = sdw_acpi_find_slaves(bus);
+	else if (IS_ENABLED(CONFIG_OF) && bus->dev->of_node)
+		ret = sdw_of_find_slaves(bus);
 	else
 		ret = -ENOTSUPP; /* No ACPI/DT so error out */
 
diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h
index 9d6ea7e447ff..cb482da914da 100644
--- a/drivers/soundwire/bus.h
+++ b/drivers/soundwire/bus.h
@@ -15,6 +15,7 @@ static inline int sdw_acpi_find_slaves(struct sdw_bus *bus)
 }
 #endif
 
+int sdw_of_find_slaves(struct sdw_bus *bus);
 void sdw_extract_slave_id(struct sdw_bus *bus,
 			  u64 addr, struct sdw_slave_id *id);
 
diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c
index 4b522f6d1238..48a63ca130d2 100644
--- a/drivers/soundwire/slave.c
+++ b/drivers/soundwire/slave.c
@@ -2,6 +2,7 @@
 // Copyright(c) 2015-17 Intel Corporation.
 
 #include <linux/acpi.h>
+#include <linux/of.h>
 #include <linux/soundwire/sdw.h>
 #include <linux/soundwire/sdw_type.h>
 #include "bus.h"
@@ -35,6 +36,7 @@ static int sdw_slave_add(struct sdw_bus *bus,
 
 	slave->dev.release = sdw_slave_release;
 	slave->dev.bus = &sdw_bus_type;
+	slave->dev.of_node = of_node_get(to_of_node(fwnode));
 	slave->bus = bus;
 	slave->status = SDW_SLAVE_UNATTACHED;
 	slave->dev_num = 0;
@@ -113,3 +115,53 @@ int sdw_acpi_find_slaves(struct sdw_bus *bus)
 }
 
 #endif
+
+/*
+ * sdw_of_find_slaves() - Find Slave devices in master device tree node
+ * @bus: SDW bus instance
+ *
+ * Scans Master DT node for SDW child Slave devices and registers it.
+ */
+int sdw_of_find_slaves(struct sdw_bus *bus)
+{
+	struct device *dev = bus->dev;
+	struct device_node *node;
+
+	for_each_child_of_node(bus->dev->of_node, node) {
+		int link_id, sdw_version, ret, len;
+		const char *compat = NULL;
+		struct sdw_slave_id id;
+		const __be32 *addr;
+
+		compat = of_get_property(node, "compatible", NULL);
+		if (!compat)
+			continue;
+
+		ret = sscanf(compat, "sdw%01x%04hx%04hx%02hhx", &sdw_version,
+			     &id.mfg_id, &id.part_id, &id.class_id);
+
+		if (ret != 4) {
+			dev_err(dev, "Invalid compatible string found %s\n",
+				compat);
+			continue;
+		}
+
+		addr = of_get_property(node, "reg", &len);
+		if (!addr || (len < 2 * sizeof(u32))) {
+			dev_err(dev, "Invalid Link and Instance ID\n");
+			continue;
+		}
+
+		link_id = be32_to_cpup(addr++);
+		id.unique_id = be32_to_cpup(addr);
+		id.sdw_version = sdw_version;
+
+		/* Check for link_id match */
+		if (link_id != bus->link_id)
+			continue;
+
+		sdw_slave_add(bus, &id, of_fwnode_handle(node));
+	}
+
+	return 0;
+}
-- 
2.21.0