PTP TX hardware timestamp timeout on Raspberry Pi CM5 (regression from 6.6 to 6.12)
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還沒有人認領這個 Issue。
評估
- 難度
- 4/5
- 預估耗時
- 3-5 天
- 新手友好度
- 48/100
- Issue 類型
- 缺陷
- 描述清晰度
- 基本清楚
- 活躍度
- 冷清
- 技術堆疊
- c, linux, raspberry-pi
研究方向
Start with drivers/net/phy/bcm-phy-ptp.c and compare the PTP TX timestamp path between rpi-6.6.y and rpi-6.12.y, focusing on bcm_ptp_txtstamp, bcm_ptp_do_aux_work, and bcm_ptp_get_tstamp. Reproduce with ptp4l -i eth0 -m while monitoring UDP ports 319 and 320 with tcpdump. Done means PHY TX timestamps no longer time out on the Raspberry Pi CM5 with the newer kernel.
由索引模型根據 Issue 內容生成。
描述
Describe the bug
Basic Information
- Hardware: Raspberry Pi CM5 + Official CM5 IO Board
- Network Port: eth0 (Cadence GEM MAC + BCM54213PE PHY)
- Regression Scope: Kernel 6.6.74 (Working) → 6.12+ (Failing)
Test Matrix
| Kernel | Provider | Result |
|---|---|---|
| rpi-6.6.y | PHY timestamp (idx 0) | PASS |
| rpi-6.12.y | PHY timestamp (idx 0) | FAIL |
| rpi-6.18.y | PHY timestamp (idx 0) | FAIL |
Symptom
- Test side
pi@raspberrypi:~ $ sudo ptp4l -i eth0 -m
ptp4l[70.739]: selected /dev/ptp0 as PTP clock
ptp4l[70.745]: port 1: INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[70.745]: port 0: INITIALIZING to LISTENING on INIT_COMPLETE
ptp4l[77.867]: port 1: LISTENING to MASTER on ANNOUNCE_RECEIPT_TIMEOUT_EXPIRES
ptp4l[77.867]: selected local clock 2ccf67.fffe.feb41d as best master
ptp4l[77.867]: port 1: assuming the grand master role
ptp4l[78.868]: timed out while polling for tx timestamp
ptp4l[78.868]: increasing tx_timestamp_timeout may correct this issue, but it is likely caused by a driver bug
ptp4l[78.868]: port 1: send sync failed
ptp4l[78.868]: port 1: MASTER to FAULTY on FAULT_DETECTED (FT_UNSPECIFIED)
- Monitoring end
pi@raspberrypi:~ $ sudo tcpdump -ni eth0 udp port 319 or udp port 320
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), snapshot length 262144 bytes
10:11:14.984307 IP 192.168.8.4.320 > 224.0.1.129.320: PTPv2, v1 compat : no, msg type : announce msg, length : 64, domain : 0, reserved1 : 0, Flags [timescale], NS correction : 0, sub NS correction : 0, reserved2 : 0, clock identity : 0x2ccf67fffefeb41d, port id : 1, seq id : 0, control : 5 (Other), log message interval : 1, originTimeStamp : 0 seconds 0 nanoseconds, origin cur utc :37, rsvd : 0, gm priority_1 : 128, gm clock class : 248, gm clock accuracy : 254, gm clock variance : 65535, gm priority_2 : 128, gm clock id : 0x2ccf67fffefeb41d, steps removed : 0, time source : 0xa0
10:11:15.983322 IP 192.168.8.4.319 > 224.0.1.129.319: PTPv2, v1 compat : no, msg type : sync msg, length : 44, domain : 0, reserved1 : 0, Flags [two step], NS correction : 0, sub NS correction : 0, reserved2 : 0, clock identity : 0x2ccf67fffefeb41d, port id : 1, seq id : 0, control : 0 (Sync), log message interval : 0, originTimeStamp : 0 seconds, 0 nanoseconds
Reproduction (minimal)
- Install the following tools：
sudo apt install tcpdump linuxptp -y
- Perform the following operations in a terminal：
sudo ptp4l -i eth0 -m
- Open a new terminal and perform the following operations：
sudo tcpdump -ni eth0 udp port 319 or udp port 320
Analysis
- drivers/net/phy/bcm-phy-ptp.c is functionally identical between rpi-6.6.y and rpi-6.18.y . The core TX timestamp logic ( bcm_ptp_txtstamp , bcm_ptp_do_aux_work , bcm_ptp_get_tstamp ) is unchanged.
- EEE is NOT the cause. ethtool --set-eee eth0 eee off does not resolve the issue.
- IRQ vs Poll mode irrelevant. Both modes fail on the newer kernels.
- Likely suspects (the regression was introduced between Linux 6.6 and 6.12)
Impact
This breaks PTP hardware timestamping via the PHY, which is required for industrial use cases requiring sub-100ns synchronization precision (motion control, IEC 61850, 5G fronthaul, TSN 802.1AS). MAC timestamps provide a lower-precision workaround (~50-200ns RGMII jitter vs <10ns for PHY timestamps).
Steps to reproduce the behaviour
- Install the following tools：
sudo apt install tcpdump linuxptp -y
- Perform the following operations in a terminal：
sudo ptp4l -i eth0 -m
- Open a new terminal and perform the following operations：
sudo tcpdump -ni eth0 udp port 319 or udp port 320
Device (s)
Raspberry Pi CM5
System
- Hardware: Raspberry Pi CM5 + Official CM5 IO Board
- Network Port: eth0 (Cadence GEM MAC + BCM54213PE PHY)
- Regression Scope: Kernel 6.6.74 (Working) → 6.12+ (Failing)
Logs
No response
Additional context
No response
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