soundwire: add sdw_show_ping_status() helper

This helper provides an optional delay parameter to wait for devices
to resync in case of errors, and checks that devices are indeed
attached on the bus.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Rander Wang <rander.wang@intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Acked-By: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20220714011043.46059-4-yung-chuan.liao@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/soundwire/bus.c

@@ -297,6 +297,38 @@ int sdw_transfer(struct sdw_bus *bus, struct sdw_msg *msg)
 	return ret;
 }
 
+/**
+ * sdw_show_ping_status() - Direct report of PING status, to be used by Peripheral drivers
+ * @bus: SDW bus
+ * @sync_delay: Delay before reading status
+ */
+void sdw_show_ping_status(struct sdw_bus *bus, bool sync_delay)
+{
+	u32 status;
+
+	if (!bus->ops->read_ping_status)
+		return;
+
+	/*
+	 * wait for peripheral to sync if desired. 10-15ms should be more than
+	 * enough in most cases.
+	 */
+	if (sync_delay)
+		usleep_range(10000, 15000);
+
+	mutex_lock(&bus->msg_lock);
+
+	status = bus->ops->read_ping_status(bus);
+
+	mutex_unlock(&bus->msg_lock);
+
+	if (!status)
+		dev_warn(bus->dev, "%s: no peripherals attached\n", __func__);
+	else
+		dev_dbg(bus->dev, "PING status: %#x\n", status);
+}
+EXPORT_SYMBOL(sdw_show_ping_status);
+
 /**
  * sdw_transfer_defer() - Asynchronously transfer message to a SDW Slave device
  * @bus: SDW bus

include/linux/soundwire/sdw.h

@@ -922,6 +922,8 @@ int sdw_bus_master_add(struct sdw_bus *bus, struct device *parent,
 		       struct fwnode_handle *fwnode);
 void sdw_bus_master_delete(struct sdw_bus *bus);
 
+void sdw_show_ping_status(struct sdw_bus *bus, bool sync_delay);
+
 /**
  * sdw_port_config: Master or Slave Port configuration
  *