Raspberry Pi 3 B+: Wi-Fi latency regression on 6.18.39+rpt-rpi-v8; 6.18.33 works
维护者通常 1 天内回复
还没有人认领这个 Issue。
评估
- 难度
- 4/5
- 预计耗时
- 3-5 天
- 新手友好度
- 45/100
- Issue 类型
- 缺陷
- 描述清晰度
- 基本清楚
- 活跃度
- 活跃
- 技术栈
- c, linux, raspberry-pi
调研方向
Start by reproducing the gateway-ping comparison on the Raspberry Pi 3 B+ with kernels 6.18.39+rpt-rpi-v8 and 6.18.33+rpt-rpi-v8, using the onboard brcmfmac adapter and the reported power-saving settings. Then investigate the kernel changes between those versions; done means identifying and correcting the regression while preserving normal latency on the affected setup.
由索引模型根据 Issue 内容生成。
描述
Describe the bug
After upgrading a Raspberry Pi 3 Model B+ from 6.18.33+rpt-rpi-v8 to 6.18.39+rpt-rpi-v8, onboard Wi-Fi exhibits a repeating latency pattern: most gateway pings take approximately 105–113 ms, interspersed with normal 4–8 ms responses.
There is no packet loss, signal strength is excellent, the system is idle, and Wi-Fi power saving is disabled.
Booting the same system into the retained 6.18.33+rpt-rpi-v8 kernel restores normal latency. No firmware, userspace, NetworkManager, access-point, or Wi-Fi profile changes were made between the decisive tests.
Results
6.18.39+rpt-rpi-v8, Wi-Fi only:
10 packets transmitted, 10 received, 0% packet loss
rtt min/avg/max/mdev = 5.360/78.668/112.640/47.331 ms
Representative responses:
107 ms
110 ms
5.36 ms
111 ms
112 ms
8.63 ms
105 ms
113 ms
5.40 ms
110 ms
6.18.33+rpt-rpi-v8, Wi-Fi only:
20 packets transmitted, 20 received, 0% packet loss
rtt min/avg/max/mdev = 2.110/6.990/39.653/7.566 ms
Apart from one 39.7 ms response, replies were normally 4–6 ms.
The working 6.18.33 test was performed on the same 5 GHz AP radio and frequency (5500 MHz) used when the problem was initially observed.
Steps to reproduce the behaviour
- Use a Raspberry Pi 3 Model B+ running 64-bit Debian 13 / Raspberry Pi OS Lite.
- Install and boot
linux-image-6.18.39+rpt-rpi-v8. - Connect using the onboard BCM4345/6 Wi-Fi adapter.
- Disable Wi-Fi power saving.
- Disconnect Ethernet.
- Run
ping -c 20 <LAN gateway>. - Observe repeating responses around 105–113 ms with periodic normal responses.
- Boot the same system into
linux-image-6.18.33+rpt-rpi-v8, without changing the Wi-Fi firmware or configuration. - Repeat the ping test.
- Observe normal latency around 4–6 ms.
Device(s)
Raspberry Pi 3 Mod. B+
System
Raspberry Pi reference 2026-04-21
Generated using pi-gen:
4ad56cc850fa60adcc7f07dc15879bc95cc1d281
stage2
Debian GNU/Linux 13.6 (trixie)
aarch64
Affected kernel:
Linux 6.18.39+rpt-rpi-v8
#1 SMP PREEMPT Debian 1:6.18.39-1+rpt1 (2026-07-29)
Working kernel:
Linux 6.18.33+rpt-rpi-v8
#1 SMP PREEMPT Debian 1:6.18.33-1+rpt1 (2026-06-01)
Firmware:
May 21 2026 11:21:57
version 288930ab4712b99596f32732664aaaeb881ef1e0
Relevant packages:
firmware-brcm80211 1:20260519-1~bpo13+1+rpt1
linux-image-6.18.33+rpt-rpi-v8 1:6.18.33-1+rpt1
linux-image-6.18.39+rpt-rpi-v8 1:6.18.39-1+rpt1
network-manager 1.52.1-1+rpt4
wireless-regdb 2026.05.30-1~deb13u1
wpasupplicant 2:2.10-24
Wi-Fi chipset and firmware:
brcmfmac: using brcm/brcmfmac43455-sdio for chip BCM4345/6
brcmfmac: Firmware: BCM4345/6 wl0: Aug 29 2023 01:47:08
version 7.45.265 (28bca26 CY)
FWID 01-b677b91b
Logs
On the working kernel, NetworkManager briefly enables power saving during initialization and then disables it as configured:
brcmfmac: brcmf_cfg80211_set_power_mgmt: power save enabled
brcmfmac: brcmf_cfg80211_set_power_mgmt: power save disabled
Both the global NetworkManager setting and active connection profile specify disabled power saving:
[connection]
wifi.powersave = 2
802-11-wireless.powersave: 2 (disable)
No brcmfmac errors, disconnects, thermal throttling, or packet loss were observed.
Additional context
The upgrade that introduced the problem changed the kernel from 6.18.33 to 6.18.39. It also updated firmware-brcm80211, but the controlled old/new kernel comparison used the same currently installed firmware package, isolating the kernel version as the changed variable.
The latency was reproduced on two different 5 GHz AP radios/channels. Signal strength was reported between 69% and 97%, including approximately -22 dBm near the access point.
This may be related generally to recent Pi 3 brcmfmac regressions, although the symptoms differ from #7337:
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