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

[Ping-Ke Shih <pkshih@realtek.com>]

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