rtl8761b usb bluetooth doesn't work following reboot until unplug/replug

The firmware is NOT loaded correctly... the "bu" file is loaded instead of the "b"

I used to have Ubuntu 21.10 and my Bluetooth USB dongle was loading rtl8761b_fw.bin.
Last week I upgraded to Ubuntu 22.04 and since then I can not use my USB dongle, it connects my Sony headphones and immediately disconnects, connects, disconnects, ...
Using sudo dmesg | grep Bluetooth, I saw
[ 10.106036] Bluetooth: hci0: RTL: examining hci_ver=0a hci_rev=000b lmp_ver=0a lmp_subver=8761
[ 10.107035] Bluetooth: hci0: RTL: rom_version status=0 version=1
[ 10.107038] Bluetooth: hci0: RTL: loading rtl_bt/rtl8761bu_fw.bin
[ 10.108050] Bluetooth: hci0: RTL: loading rtl_bt/rtl8761bu_config.bin
[ 10.108170] Bluetooth: hci0: RTL: cfg_sz 6, total sz 27814
So kernel 5.15 loads different firmware rtl8761bu instead of rtl8761b used by kernel 5.13 in Ubuntu 21.10.
I guess this is a kernel bug.

As a workaround I made symbolic links and now my Bluetooth USB dongle works fine:
/lib/firmware/rtl_bt$ ls -al *8761*
lrwxrwxrwx 1 root root 19 Apr 10 06:32 rtl8761bu_config.bin -> rtl8761b_config.bin
lrwxrwxrwx 1 root root 15 Apr 10 06:32 rtl8761bu_fw.bin -> rtl8761b_fw.bin

Status changed to 'Confirmed' because the bug affects multiple users.

There are two different chip versions: rtl8761btv and rtl8761buv. 'btv' is UART attached, 'buv' is USB attached. Kernel 5.15 is correct in that it loads the 'bu' firmware for your USB dongle. 5.13 is wrong. But might be that the firmware blobs are named incorrectly. Need to dig some more and probably get my hands on one of those dongles.

Update on Ubuntu 22.10 beta with kernel 5.19
Same issue as kernel 5.15 and same solution with symbolic links so that "bu" is in fact "b".

Same here, in Linux mint 21.3, @bert.ram.aerts thanks for workaround!

Also see https://fosspost.org/fix-bluetooth-rtl8761b-problem-on-linux-ubuntu-22-04/. From the article:

<SNIP>
This happens because the rtl8761bu firmware is being requested, but the system should have loaded the rtl8761b firmware, not the rtl8761bu one. The latter may not even exist on your system.

To fix this issue, luckily we don’t need to install or download anything! We just need to create a simple symbolic link to link rtl8761bu driver firmware to rtl8761b one. In this way, any time our system requests the rtl8761bu files it will be instead served the correct rtl8761b ones.

We can do it by applying the following commands in the terminal:

cd /lib/firmware/rtl_bt
sudo ln -s rtl8761b_config.bin rtl8761bu_config.bin
sudo ln -s rtl8761b_fw.bin rtl8761bu_fw.bin

After it, just remove the Bluetooth 5.0 adapter from the computer and plug it again (no restart required), and this time, it should be working.
</SNIP>

Even though all the documentation suggests otherwise, it does look like the driver loads the wrong firmware (or the firmware names as incorrect). I've contacted realtek, we'll see where that goes...

Realtek promised to release new FW for RT8761 since what is currently in kernel.org linux-firmware is over 2 years old.

Update on Ubuntu 23.04 beta with kernel 6.2
Bluetooth works out of the box, no need for the earlier symbolic links anymore!
So the rtl8761bu is now used and works with my USB dongle.

New firmware available on
https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/commit/?id=1de22a39246513ce431de0971a6376093a94c5c1
Release Version: 0xDFC6_D922
Again rtl8761bu is working fine with my USB dongle.

Hello Olga, or anyone else affected,

Accepted linux-firmware into jammy-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/linux-firmware/20220329.git681281e4-0ubuntu3.14 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-jammy to verification-done-jammy. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-jammy. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

Hello Olga, or anyone else affected,

Accepted linux-firmware into kinetic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/linux-firmware/20220923.gitf09bebf3-0ubuntu1.7 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-kinetic to verification-done-kinetic. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-kinetic. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

Hello Olga, or anyone else affected,

Accepted linux-firmware into lunar-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/linux-firmware/20230323.gitbcdcfbcf-0ubuntu1.2 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-lunar to verification-done-lunar. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-lunar. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

hi, it's been a week, please test the update

I've done some limited testing with a USB dongle that has that chip and was able to establish a BT connection.

Which package builds of linux-firmware did you test please? All three? Just one?

Sorry, missed your comment/question.

I've tested Lunar (20230323.gitbcdcfbcf-0ubuntu1.2) and Jammy (20220329.git681281e4-0ubuntu3.14) and verified that I can establish a Bluetooth connection using the new firmware.

I'm fairly certain I've run the test for kinetic (20220923.gitf09bebf3-0ubuntu1.7) as well but can't find my notes. Let me redo it.

OK, verified that I can establish a bluetooth connection on Kinetic with 20220923.gitf09bebf3-0ubuntu1.7.

This bug was fixed in the package linux-firmware - 20230323.gitbcdcfbcf-0ubuntu1.2

---------------
linux-firmware (20230323.gitbcdcfbcf-0ubuntu1.2) lunar; urgency=medium

  * rtl8761b usb bluetooth doesn't work following reboot until unplug/replug (LP: #1968604)
    - rtl_bt: Update RTL8761B BT UART firmware to 0x9DC6_D922
    - rtl_bt: Update RTL8761B BT USB firmware to 0xDFC6_D922

 -- Juerg Haefliger <email address hidden> Mon, 05 Jun 2023 09:22:50 +0200

The verification of the Stable Release Update for linux-firmware has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.

This bug was fixed in the package linux-firmware - 20220923.gitf09bebf3-0ubuntu1.7

---------------
linux-firmware (20220923.gitf09bebf3-0ubuntu1.7) kinetic; urgency=medium

  * rtl8761b usb bluetooth doesn't work following reboot until unplug/replug (LP: #1968604)
    - rtl_bt: Update RTL8761B BT UART firmware to 0x9DC6_D922
    - rtl_bt: Update RTL8761B BT USB firmware to 0xDFC6_D922

 -- Juerg Haefliger <email address hidden> Mon, 05 Jun 2023 09:29:22 +0200

This bug was fixed in the package linux-firmware - 20220329.git681281e4-0ubuntu3.14

---------------
linux-firmware (20220329.git681281e4-0ubuntu3.14) jammy; urgency=medium

  * rtl8761b usb bluetooth doesn't work following reboot until unplug/replug (LP: #1968604)
    - rtl_bt: Update RTL8761B BT UART firmware to 0x9DC6_D922
    - rtl_bt: Update RTL8761B BT USB firmware to 0xDFC6_D922

 -- Juerg Haefliger <email address hidden> Mon, 05 Jun 2023 09:32:37 +0200