Add bridged amplifiers to cs42l43

Merge series from Charles Keepax <ckeepax@opensource.cirrus.com>:

In some cs42l43 systems a couple of cs35l56 amplifiers are attached
to the cs42l43's SPI and I2S. On Windows the cs42l43 is controlled
by a SDCA class driver and these two amplifiers are controlled by
firmware running on the cs42l43. However, under Linux the decision
was made to interact with the cs42l43 directly, affording the user
greater control over the audio system. However, this has resulted
in an issue where these two bridged cs35l56 amplifiers are not
populated in ACPI and must be added manually. There is at least an
SDCA extension unit DT entry we can key off.

The process of adding this is handled using a software node, firstly the
ability to add native chip selects to software nodes must be added.
Secondly, an additional flag for naming the SPI devices is added this
allows the machine driver to key to the correct amplifier. Then finally,
the cs42l43 SPI driver adds the two amplifiers directly onto its SPI
bus.

An additional series will follow soon to add the audio machine driver
parts (in the sof-sdw driver), however that is fairly orthogonal to
this part of the process, getting the actual amplifiers registered.

1 files changed, 23 insertions, 3 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index b93f3c5716ae..5f4e03336e68 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -44,6 +44,7 @@ static bool fw_devlink_is_permissive(void);
 static void __fw_devlink_link_to_consumers(struct device *dev);
 static bool fw_devlink_drv_reg_done;
 static bool fw_devlink_best_effort;
+static struct workqueue_struct *device_link_wq;
 
 /**
  * __fwnode_link_add - Create a link between two fwnode_handles.
@@ -533,12 +534,26 @@ static void devlink_dev_release(struct device *dev)
 	/*
 	 * It may take a while to complete this work because of the SRCU
 	 * synchronization in device_link_release_fn() and if the consumer or
-	 * supplier devices get deleted when it runs, so put it into the "long"
-	 * workqueue.
+	 * supplier devices get deleted when it runs, so put it into the
+	 * dedicated workqueue.
 	 */
-	queue_work(system_long_wq, &link->rm_work);
+	queue_work(device_link_wq, &link->rm_work);
 }
 
+/**
+ * device_link_wait_removal - Wait for ongoing devlink removal jobs to terminate
+ */
+void device_link_wait_removal(void)
+{
+	/*
+	 * devlink removal jobs are queued in the dedicated work queue.
+	 * To be sure that all removal jobs are terminated, ensure that any
+	 * scheduled work has run to completion.
+	 */
+	flush_workqueue(device_link_wq);
+}
+EXPORT_SYMBOL_GPL(device_link_wait_removal);
+
 static struct class devlink_class = {
 	.name = "devlink",
 	.dev_groups = devlink_groups,
@@ -4164,9 +4179,14 @@ int __init devices_init(void)
 	sysfs_dev_char_kobj = kobject_create_and_add("char", dev_kobj);
 	if (!sysfs_dev_char_kobj)
 		goto char_kobj_err;
+	device_link_wq = alloc_workqueue("device_link_wq", 0, 0);
+	if (!device_link_wq)
+		goto wq_err;
 
 	return 0;
 
+ wq_err:
+	kobject_put(sysfs_dev_char_kobj);
  char_kobj_err:
 	kobject_put(sysfs_dev_block_kobj);
  block_kobj_err: