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From:   Jose Ignacio Tornos Martinez <jtornosm@redhat.com>
To:     marcel@holtmann.org, johan.hedberg@gmail.com, luiz.dentz@gmail.com,
        linux-bluetooth@vger.kernel.org
Cc:     Jose Ignacio Tornos Martinez <jtornosm@redhat.com>
Subject: [PATCH] btusb: CSR chip hangs when unbound
Date:   Fri, 29 Apr 2022 13:41:13 +0200
Message-Id: <20220429114113.356263-1-jtornosm@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Bluetooth Dongles with CSR chip (i.e. USB Bluetooth V4.0 Dongle by Trust)
hang when they are unbound from 'unbind' sysfs entry and can not be bound
again.

The reason is CSR chip hangs when usb configuration command with index 0 
(used to unconfigure) is sent during disconnection.

To avoid this unwanted result, it is necessary not to send this command 
for CSR chip when usb device is unbound. Besides, "skip_unconfigure"  sysfs 
entry has been created for testing purposes with these or other devices.

Athough device is not unconfigured, it is better to avoid device hanging to
be able to operate. Even bluetooth can be previously turned off.
On the other hand, this is not important if usb device is going to be bound 
again (normal behavior), i.e. with usbip.

Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@redhat.com>
---
 drivers/bluetooth/btusb.c  |  6 ++++++
 drivers/usb/core/generic.c |  2 +-
 drivers/usb/core/sysfs.c   | 36 ++++++++++++++++++++++++++++++++++++
 include/linux/usb.h        |  2 ++
 4 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index b7c72eb96c87..7eb951e47dc2 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -4836,7 +4836,13 @@ static int btusb_probe(struct usb_interface *intf,
 		/* Fake CSR devices with broken commands */
 		if (le16_to_cpu(udev->descriptor.idVendor)  == 0x0a12 &&
 		    le16_to_cpu(udev->descriptor.idProduct) == 0x0001)
+		{
 			hdev->setup = btusb_setup_csr;
+			/* This device hangs when configuration command with
+                         * index 0 (unconfigure) is sent, avoid this at least
+                         * if it is unbound */
+			udev->skip_unconfigure = 1;
+		}
 	}
 
 	if (id->driver_info & BTUSB_SNIFFER) {
diff --git a/drivers/usb/core/generic.c b/drivers/usb/core/generic.c
index 26f9fb9f67ca..f25171284119 100644
--- a/drivers/usb/core/generic.c
+++ b/drivers/usb/core/generic.c
@@ -256,7 +256,7 @@ void usb_generic_driver_disconnect(struct usb_device *udev)
 
 	/* if this is only an unbind, not a physical disconnect, then
 	 * unconfigure the device */
-	if (udev->actconfig)
+	if (!udev->skip_unconfigure && udev->actconfig)
 		usb_set_configuration(udev, -1);
 }
 
diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index fa2e49d432ff..7cecc558e2c4 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -1189,6 +1189,41 @@ static struct device_attribute dev_attr_interface_authorized =
 		__ATTR(authorized, S_IRUGO | S_IWUSR,
 		interface_authorized_show, interface_authorized_store);
 
+static ssize_t skip_unconfigure_show(struct device *dev,
+                                      struct device_attribute *attr, char *buf)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_device *udev = interface_to_usbdev(intf);
+	int val;
+
+	if (usb_lock_device_interruptible(udev) < 0)
+		return -EINTR;
+	val = udev->skip_unconfigure;
+	usb_unlock_device(udev);
+
+	return sprintf(buf, "%d\n", val);
+}
+
+static ssize_t skip_unconfigure_store(struct device *dev,
+                                      struct device_attribute *attr,
+                                      const char *buf, size_t count)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_device *udev = interface_to_usbdev(intf);
+	int val;
+
+	if (sscanf(buf, "%d", &val) != 1 || val < 0 || val > 1)
+		return -EINVAL;
+
+	if (usb_lock_device_interruptible(udev) < 0)
+		return -EINTR;
+	udev->skip_unconfigure = val;
+	usb_unlock_device(udev);
+
+	return count;
+}
+static DEVICE_ATTR_RW(skip_unconfigure);
+
 static struct attribute *intf_attrs[] = {
 	&dev_attr_bInterfaceNumber.attr,
 	&dev_attr_bAlternateSetting.attr,
@@ -1199,6 +1234,7 @@ static struct attribute *intf_attrs[] = {
 	&dev_attr_modalias.attr,
 	&dev_attr_supports_autosuspend.attr,
 	&dev_attr_interface_authorized.attr,
+	&dev_attr_skip_unconfigure.attr,
 	NULL,
 };
 static const struct attribute_group intf_attr_grp = {
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 86a73d834e38..55828cd0a0d1 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -618,6 +618,7 @@ struct usb3_lpm_parameters {
  *	parent->hub_delay + wHubDelay + tTPTransmissionDelay (40ns)
  *	Will be used as wValue for SetIsochDelay requests.
  * @use_generic_driver: ask driver core to reprobe using the generic driver.
+ * @skip_unconfigure: disable unconfigure operation for devices without support.
  *
  * Notes:
  * Usbcore drivers should not set usbdev->state directly.  Instead use
@@ -704,6 +705,7 @@ struct usb_device {
 
 	u16 hub_delay;
 	unsigned use_generic_driver:1;
+	unsigned skip_unconfigure:1;
 };
 #define	to_usb_device(d) container_of(d, struct usb_device, dev)
 
-- 
2.27.0