[BUG] rtw89: 8852be intermittent 2.4GHz packet loss regression 7.0.12 -> 7.1.x

[BUG] rtw89: 8852be intermittent 2.4GHz packet loss regression 7.0.12 -> 7.1.x

[nurofen55]

Hi,
I'd like to report a regression in the rtw89 driver (RTL8852BE) affecting 2.4GHz stability, introduced somewhere between kernel 7.0.12 and 7.1.x. This was originally filed on openSUSE bugzilla (bug 1271359), and Jiri Slaby suggested I forward it here for visibility with the driver maintainers:
https://bugzilla.opensuse.org/show_bug.cgi?id\x1271359
Summary:

After updating from kernel 7.0.12 to the 7.1.x series (tested on 7.1.2 and 7.1.3) on openSUSE Tumbleweed, intermittent connectivity issues appear specifically on the 2.4GHz band. On kernel 7.0.12, both 2.4GHz and 5GHz bands were equally stable at the same physical location. On kernel 7.1.x, the 5GHz band remains fully stable at the same location, while the 2.4GHz band exhibits intermittent high-latency/packet-loss events.
Hardware:

- Laptop: Lenovo IdeaPad Slim 3 15ARP10

- CPU: AMD Ryzen 7 7735HS

- Wi-Fi: Realtek RTL8852BE (rtw89_8852be), PCIe

- Firmware: rtw89/rtw8852b_fw-2.bin, version 0.29.29.18 (9e3d777f) - unchanged throughout all testing (ruled out as a factor)
Steps to reproduce:

1. Boot into kernel 7.1.x (reproduced on both 7.1.2 and 7.1.3)

2. Connect to the 2.4GHz SSID at a location with moderate signal (around -70 dBm)

3. Run continuous monitoring (mtr/ping) while using the connection normally

4. Intermittent packet loss / latency spikes occur; the same location/conditions on the 5GHz SSID show no such issue
Captured evidence of one event (kernel 7.1.3), mtr output during the drop:
HOST: localhost.localdomain    Loss%   Snt   Last   Avg   Best  Wrst  StDev

1.|-- 192.168.0.109            20.0%    10   3018.  958.6  9.0  3018. 1234.6

     192.168.0.1
A single packet showed about 3018 ms latency with 20% loss recorded during the sample.
Notably, no corresponding entries appear in dmesg/journalctl during this event - no deauth, no driver error, no firmware timeout. iw dev wlp2s0 station dump immediately after showed the link as fully healthy: 0 tx retries, 0 tx failed, beacon loss 0. This suggests the packet loss happens at a level not surfaced by driver logging (possibly interference handling, channel contention, or power-save logic specific to 2.4GHz), rather than a link-layer disconnect.
Expected behavior:

2.4GHz stability matching kernel 7.0.12 behavior (equivalent to current 5GHz stability on 7.1.x).
Actual behavior:

Intermittent high-latency/packet-loss events on 2.4GHz only, with kernel 7.1.x; not reproduced on 5GHz under the same conditions; not reproduced on 2.4GHz under kernel 7.0.12.
Additional info:

Kernel 7.0.12 is no longer installable via zypper in the current Tumbleweed OSS repo, so I'm currently unable to do further direct A/B testing against 7.0.12 - this report is based on testing done while 7.0.12 was still available. I understand older builds may still be available via download.opensuse.org/history if a fresh comparison is needed.
I'm happy to test patches, run bisection guidance, or gather any additional debug output (debugfs, ethtool stats, etc.) if that would help narrow this down.
Thanks,

Sviatoslav

RE: [BUG] rtw89: 8852be intermittent 2.4GHz packet loss regression 7.0.12 -> 7.1.x

[Ping-Ke Shih]

nurofen55@meta.ua <nurofen55@meta.ua> wrote:
> Hi,
> I'd like to report a regression in the rtw89 driver (RTL8852BE) affecting 2.4GHz stability, introduced
> somewhere between kernel 7.0.12 and 7.1.x. This was originally filed on openSUSE bugzilla (bug 1271359),
> and Jiri Slaby suggested I forward it here for visibility with the driver maintainers:
> https://bugzilla.opensuse.org/show_bug.cgi?id\x1271359
> Summary:
> 
> After updating from kernel 7.0.12 to the 7.1.x series (tested on 7.1.2 and 7.1.3) on openSUSE Tumbleweed,
> intermittent connectivity issues appear specifically on the 2.4GHz band. On kernel 7.0.12, both 2.4GHz
> and 5GHz bands were equally stable at the same physical location. On kernel 7.1.x, the 5GHz band remains
> fully stable at the same location, while the 2.4GHz band exhibits intermittent high-latency/packet-loss
> events.
> Hardware:
> 
> - Laptop: Lenovo IdeaPad Slim 3 15ARP10
> 
> - CPU: AMD Ryzen 7 7735HS
> 
> - Wi-Fi: Realtek RTL8852BE (rtw89_8852be), PCIe
> 
> - Firmware: rtw89/rtw8852b_fw-2.bin, version 0.29.29.18 (9e3d777f) - unchanged throughout all testing

Please check the kernel to see the firmware it actually loaded.

The commit 1d67f1f8e9a0 ("wifi: rtw89: 8852b: update supported firmware format to 2")
added by 7.1 is changed to support -2 firmware. That means kernel 7.0 loads
rtw89/rtw8852b_fw.bin instead.

> (ruled out as a factor)
> Steps to reproduce:
> 
> 1. Boot into kernel 7.1.x (reproduced on both 7.1.2 and 7.1.3)
> 
> 2. Connect to the 2.4GHz SSID at a location with moderate signal (around -70 dBm)

If you locate your laptop nearby the AP (stronger signal), will it be improved?

Please also try to turn off power save by
   sudo iw wlan0 set power_save off
to see if anything changes. 

> 
> 3. Run continuous monitoring (mtr/ping) while using the connection normally
> 
> 4. Intermittent packet loss / latency spikes occur; the same location/conditions on the 5GHz SSID show
> no such issue
> Captured evidence of one event (kernel 7.1.3), mtr output during the drop:
> HOST: localhost.localdomain    Loss%   Snt   Last   Avg   Best  Wrst  StDev
> 
> 1.|-- 192.168.0.109            20.0%    10   3018.  958.6  9.0  3018. 1234.6
> 
>      192.168.0.1
> A single packet showed about 3018 ms latency with 20% loss recorded during the sample.
> Notably, no corresponding entries appear in dmesg/journalctl during this event - no deauth, no driver
> error, no firmware timeout. iw dev wlp2s0 station dump immediately after showed the link as fully healthy:
> 0 tx retries, 0 tx failed, beacon loss 0. This suggests the packet loss happens at a level not surfaced
> by driver logging (possibly interference handling, channel contention, or power-save logic specific
> to 2.4GHz), rather than a link-layer disconnect.
> Expected behavior:
> 
> 2.4GHz stability matching kernel 7.0.12 behavior (equivalent to current 5GHz stability on 7.1.x).
> Actual behavior:
> 
> Intermittent high-latency/packet-loss events on 2.4GHz only, with kernel 7.1.x; not reproduced on 5GHz
> under the same conditions; not reproduced on 2.4GHz under kernel 7.0.12.
> Additional info:
> 
> Kernel 7.0.12 is no longer installable via zypper in the current Tumbleweed OSS repo, so I'm currently
> unable to do further direct A/B testing against 7.0.12 - this report is based on testing done while
> 7.0.12 was still available. I understand older builds may still be available via
> download.opensuse.org/history if a fresh comparison is needed.
> I'm happy to test patches, run bisection guidance, or gather any additional debug output (debugfs,
> ethtool stats, etc.) if that would help narrow this down.

The commit bda294ed0ed0 ("wifi: rtw89: Drop malformed AMPDU frames with abnormal PN")
introduced by 7.0 with a bug, so we have another commit
63ccdfac8677 ("wifi: rtw89: correct drop logic for malformed AMPDU frames")
to fix it. 

Could you please apply 63ccdfac8677 to 7.1.x? 

Since I have reviewed changes between 7.0 and 7.1, if these suggestions
don't work, please help to bisect the cause. 

Ping-Ke