[PATCH v2 01/18] soundwire: Add a helper function to wait for device initialisation

[Charles Keepax <ckeepax@opensource.cirrus.com>]

Add a new helper function to wait for the device to enumerate
and be initialised by the SoundWire core. Most of the SoundWire
drivers have very similar boiler plate code in their runtime
resume, and that boiler plate tends to access various internals
of the SoundWire structs which is a mild layering violation.

Adding a new core helper function greatly eases both of these
issues.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
---

Changes since v1:
 - Add stub for when soundwire not built in.
 - Add missing kerneldoc

 drivers/soundwire/bus.c       | 31 +++++++++++++++++++++++++++++++
 include/linux/soundwire/sdw.h |  8 ++++++++
 2 files changed, 39 insertions(+)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index fe5316d93fefe..037c51a3874ea 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -1372,6 +1372,37 @@ int sdw_slave_get_current_bank(struct sdw_slave *slave)
 }
 EXPORT_SYMBOL_GPL(sdw_slave_get_current_bank);
 
+/**
+ * sdw_slave_wait_for_init - Wait for device initialisation
+ * @slave: Pointer to the SoundWire peripheral.
+ * @timeout_us: Timeout in microseconds.
+ *
+ * Wait for a peripheral device to enumerate and be initialised by the
+ * SoundWire core.
+ *
+ * Return: Zero on success, and a negative error code on failure.
+ */
+int sdw_slave_wait_for_init(struct sdw_slave *slave, int timeout_us)
+{
+	unsigned long time;
+
+	if (!slave->unattach_request)
+		return 0;
+
+	time = wait_for_completion_timeout(&slave->initialization_complete,
+					   msecs_to_jiffies(timeout_us));
+	if (!time) {
+		dev_err(&slave->dev, "Initialization not complete\n");
+		sdw_show_ping_status(slave->bus, true);
+		return -ETIMEDOUT;
+	}
+
+	slave->unattach_request = 0;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(sdw_slave_wait_for_init);
+
 static int sdw_slave_set_frequency(struct sdw_slave *slave)
 {
 	int scale_index;
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index 6147eb1fb210d..7e5818d989294 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -1093,6 +1093,8 @@ int sdw_slave_get_current_bank(struct sdw_slave *sdev);
 
 int sdw_slave_get_scale_index(struct sdw_slave *slave, u8 *base);
 
+int sdw_slave_wait_for_init(struct sdw_slave *slave, int timeout);
+
 /* messaging and data APIs */
 int sdw_read(struct sdw_slave *slave, u32 addr);
 int sdw_write(struct sdw_slave *slave, u32 addr, u8 value);
@@ -1136,6 +1138,12 @@ static inline int sdw_slave_get_current_bank(struct sdw_slave *sdev)
 	return -EINVAL;
 }
 
+static inline int sdw_slave_wait_for_init(struct sdw_slave *slave, int timeout)
+{
+	WARN_ONCE(1, "SoundWire API is disabled");
+	return -EINVAL;
+}
+
 /* messaging and data APIs */
 static inline int sdw_read(struct sdw_slave *slave, u32 addr)
 {
-- 
2.47.3