Hi all,
I face a strange issue with 5G Modems in this slot. The slot seems to work fine if I install a M.2 adapter with a M.2 NIC 2.5 Gbps. I can get full speed both directions via Ethernet port.
But if I connect a 5G modem like FM350-GL or Dell DW5934e into this slot I get some errors like this:
[ 74.858008] mtk_t7xx 0003:01:00.0: MD handshake timeout
[ 74.863243] mtk_t7xx 0003:01:00.0: Boot Handshake failure
[ 85.032006] pcieport 0003:00:00.0: AER: Correctable error message received from 0003:00:00.0
[ 85.040463] pcieport 0003:00:00.0: PCIe Bus Error: severity=Correctable, type=Physical Layer, (Receiver ID)
[ 85.050200] pcieport 0003:00:00.0: device [14c3:7988] error status/mask=00000001/00006000
[ 85.058549] pcieport 0003:00:00.0: [ 0] RxErr (First)
[ 85.080389] pcieport 0003:00:00.0: AER: Uncorrectable (Fatal) error message received from 0003:00:00.0
[ 85.089709] pcieport 0003:00:00.0: PCIe Bus Error: severity=Uncorrectable (Fatal), type=Transaction Layer, (Receiver ID)
[ 85.100573] pcieport 0003:00:00.0: device [14c3:7988] error status/mask=00000020/00400000
[ 85.108919] pcieport 0003:00:00.0: [ 5] SDES (First)
[ 85.115703] pcieport 0003:00:00.0: AER: broadcast error_detected message
[ 85.122399] mtk_t7xx 0003:01:00.0: AER: can't recover (no error_detected callback)
[ 85.147996] pcieport 0003:00:00.0: waiting 100 ms for downstream link, after activation
[ 86.177996] pcieport 0003:00:00.0: broken device, retraining non-functional downstream link at 2.5GT/s
[ 86.337485] mtk_t7xx 0003:01:00.0: ready 0ms after bus reset
[ 86.343149] pcieport 0003:00:00.0: AER: Root Port link has been reset (0)
[ 86.349987] pcieport 0003:00:00.0: AER: device recovery failed
Or sometimes it doesn’t get this error but the driver mtk_t7xx is loaded but it doesn’t expose any kind of /dev/wwan0* interface.
On my Ryzen 5900X PC with a PCIe to M.2 B+M adapter and then M.2 Key B with SIM to M.2 Key B+M, the modem works OK with mtk_t7xx and it expose /dev/wwan0* interfaces.
The only difference between these 2 setups is the second one doesn’t have an USB 2.0/3.0 interface, so in my Ryzen 5900X works only in PCIe mode.
Both Ryzen 5900X and BPi R4 are running Kernel 7.1.x:
root@EasyOS:/# uname -a
Linux EasyOS 7.1.2-EasyOS-bpi-r4 #1 SMP PREEMPT Fri Jul 3 17:55:33 CEST 2026 aarch64 GNU/Linux
root@Ryzen5900X:~# uname -a
Linux Ryzen5900X 7.1-amd64 #1 SMP PREEMPT_DYNAMIC Debian 7.1.1-1~exp1 (2026-06-19) x86_64 GNU/Linux
But in BPi R4 I can see modem on both interfaces: PCIe and USB.
And in logs I get:
# dmesg | grep mtk_t7xx
[ 13.112835] mtk_t7xx 0003:01:00.0: vgaarb: pci_notify
[ 13.123268] mtk_t7xx 0003:01:00.0: assign IRQ: got 120
[ 13.128529] mtk_t7xx 0003:01:00.0: enabling device (0000 -> 0002)
[ 13.134632] mtk_t7xx 0003:01:00.0: enabling bus mastering
[ 13.361667] mtk_t7xx 0003:01:00.0: vgaarb: pci_notify
[ 74.840882] mtk_t7xx 0003:01:00.0: MD handshake timeout
[ 74.846119] mtk_t7xx 0003:01:00.0: Boot Handshake failure
I tried to disable all USB drivers for FM350-GL in /etc/modprobe.d/blacklist-mtk-usb.conf:
# Blacklist for USB driver for FM350-GL
blacklist option
blacklist cdc_acm
blacklist cdc_mbim
blacklist cdc_wdm
Also /etc/udev/rules.d/99-disable-mtk-usb.rules:
# Disable USB interfaces for FM350-GL (0e8d:7127)
ATTR{idVendor}=="0e8d", ATTR{idProduct}=="7127", ATTR{authorized}="0"
//LE If I don’t load any USB drivers, the PCIe works better, mtk_t7xx is loaded but doesn’t expose any /dev/wwan0* interface.
Any ideas?
