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.

4 files changed, 65 insertions, 14 deletions

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 3ee8455585b6..9446660e231b 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -130,7 +130,6 @@ EXPORT_SYMBOL_GPL(ehci_cf_port_reset_rwsem);
 #define HUB_DEBOUNCE_STEP	  25
 #define HUB_DEBOUNCE_STABLE	 100
 
-static void hub_release(struct kref *kref);
 static int usb_reset_and_verify_device(struct usb_device *udev);
 static int hub_port_disable(struct usb_hub *hub, int port1, int set_state);
 static bool hub_port_warm_reset_required(struct usb_hub *hub, int port1,
@@ -720,14 +719,14 @@ static void kick_hub_wq(struct usb_hub *hub)
 	 */
 	intf = to_usb_interface(hub->intfdev);
 	usb_autopm_get_interface_no_resume(intf);
-	kref_get(&hub->kref);
+	hub_get(hub);
 
 	if (queue_work(hub_wq, &hub->events))
 		return;
 
 	/* the work has already been scheduled */
 	usb_autopm_put_interface_async(intf);
-	kref_put(&hub->kref, hub_release);
+	hub_put(hub);
 }
 
 void usb_kick_hub_wq(struct usb_device *hdev)
@@ -1095,7 +1094,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
 			goto init2;
 		goto init3;
 	}
-	kref_get(&hub->kref);
+	hub_get(hub);
 
 	/* The superspeed hub except for root hub has to use Hub Depth
 	 * value as an offset into the route string to locate the bits
@@ -1343,7 +1342,7 @@ static void hub_activate(struct usb_hub *hub, enum hub_activation_type type)
 		device_unlock(&hdev->dev);
 	}
 
-	kref_put(&hub->kref, hub_release);
+	hub_put(hub);
 }
 
 /* Implement the continuations for the delays above */
@@ -1759,6 +1758,16 @@ static void hub_release(struct kref *kref)
 	kfree(hub);
 }
 
+void hub_get(struct usb_hub *hub)
+{
+	kref_get(&hub->kref);
+}
+
+void hub_put(struct usb_hub *hub)
+{
+	kref_put(&hub->kref, hub_release);
+}
+
 static unsigned highspeed_hubs;
 
 static void hub_disconnect(struct usb_interface *intf)
@@ -1807,7 +1816,7 @@ static void hub_disconnect(struct usb_interface *intf)
 
 	onboard_hub_destroy_pdevs(&hub->onboard_hub_devs);
 
-	kref_put(&hub->kref, hub_release);
+	hub_put(hub);
 }
 
 static bool hub_descriptor_is_sane(struct usb_host_interface *desc)
@@ -5934,7 +5943,7 @@ out_hdev_lock:
 
 	/* Balance the stuff in kick_hub_wq() and allow autosuspend */
 	usb_autopm_put_interface(intf);
-	kref_put(&hub->kref, hub_release);
+	hub_put(hub);
 
 	kcov_remote_stop();
 }
diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
index 43ce21c96a51..183b69dc2955 100644
--- a/drivers/usb/core/hub.h
+++ b/drivers/usb/core/hub.h
@@ -129,6 +129,8 @@ extern void usb_hub_remove_port_device(struct usb_hub *hub,
 extern int usb_hub_set_port_power(struct usb_device *hdev, struct usb_hub *hub,
 		int port1, bool set);
 extern struct usb_hub *usb_hub_to_struct_hub(struct usb_device *hdev);
+extern void hub_get(struct usb_hub *hub);
+extern void hub_put(struct usb_hub *hub);
 extern int hub_port_debounce(struct usb_hub *hub, int port1,
 		bool must_be_connected);
 extern int usb_clear_port_feature(struct usb_device *hdev,
diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 5b5e613a11e5..686c01af03e6 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -56,11 +56,22 @@ static ssize_t disable_show(struct device *dev,
 	u16 portstatus, unused;
 	bool disabled;
 	int rc;
+	struct kernfs_node *kn;
 
+	hub_get(hub);
 	rc = usb_autopm_get_interface(intf);
 	if (rc < 0)
-		return rc;
+		goto out_hub_get;
 
+	/*
+	 * Prevent deadlock if another process is concurrently
+	 * trying to unregister hdev.
+	 */
+	kn = sysfs_break_active_protection(&dev->kobj, &attr->attr);
+	if (!kn) {
+		rc = -ENODEV;
+		goto out_autopm;
+	}
 	usb_lock_device(hdev);
 	if (hub->disconnected) {
 		rc = -ENODEV;
@@ -70,9 +81,13 @@ static ssize_t disable_show(struct device *dev,
 	usb_hub_port_status(hub, port1, &portstatus, &unused);
 	disabled = !usb_port_is_power_on(hub, portstatus);
 
-out_hdev_lock:
+ out_hdev_lock:
 	usb_unlock_device(hdev);
+	sysfs_unbreak_active_protection(kn);
+ out_autopm:
 	usb_autopm_put_interface(intf);
+ out_hub_get:
+	hub_put(hub);
 
 	if (rc)
 		return rc;
@@ -90,15 +105,26 @@ static ssize_t disable_store(struct device *dev, struct device_attribute *attr,
 	int port1 = port_dev->portnum;
 	bool disabled;
 	int rc;
+	struct kernfs_node *kn;
 
 	rc = kstrtobool(buf, &disabled);
 	if (rc)
 		return rc;
 
+	hub_get(hub);
 	rc = usb_autopm_get_interface(intf);
 	if (rc < 0)
-		return rc;
+		goto out_hub_get;
 
+	/*
+	 * Prevent deadlock if another process is concurrently
+	 * trying to unregister hdev.
+	 */
+	kn = sysfs_break_active_protection(&dev->kobj, &attr->attr);
+	if (!kn) {
+		rc = -ENODEV;
+		goto out_autopm;
+	}
 	usb_lock_device(hdev);
 	if (hub->disconnected) {
 		rc = -ENODEV;
@@ -119,9 +145,13 @@ static ssize_t disable_store(struct device *dev, struct device_attribute *attr,
 	if (!rc)
 		rc = count;
 
-out_hdev_lock:
+ out_hdev_lock:
 	usb_unlock_device(hdev);
+	sysfs_unbreak_active_protection(kn);
+ out_autopm:
 	usb_autopm_put_interface(intf);
+ out_hub_get:
+	hub_put(hub);
 
 	return rc;
 }
diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index f98263e21c2a..d83231d6736a 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -1217,14 +1217,24 @@ static ssize_t interface_authorized_store(struct device *dev,
 {
 	struct usb_interface *intf = to_usb_interface(dev);
 	bool val;
+	struct kernfs_node *kn;
 
 	if (kstrtobool(buf, &val) != 0)
 		return -EINVAL;
 
-	if (val)
+	if (val) {
 		usb_authorize_interface(intf);
-	else
-		usb_deauthorize_interface(intf);
+	} else {
+		/*
+		 * Prevent deadlock if another process is concurrently
+		 * trying to unregister intf.
+		 */
+		kn = sysfs_break_active_protection(&dev->kobj, &attr->attr);
+		if (kn) {
+			usb_deauthorize_interface(intf);
+			sysfs_unbreak_active_protection(kn);
+		}
+	}
 
 	return count;
 }