RM520N-GL: latest Linux PCIe MHI driver + data stall on congested cells

Technical Subjects Driver
1

Hello,

I’m running an RM520N-GL (firmware RM520NGLAAR03A04M4G) over PCIe on an OpenWrt router (MediaTek MT7981, kernel 6.18), using Quectel_Linux_PCIE_MHI_Driver V1.3.8 with quectel-CM V1.6.8 (QMI/QMAP, qmap_mode=1).

  1. Is there a PCIe MHI driver newer than V1.3.8? Please send it with its release notes.

  2. On a congested LTE/NSA cell the data call comes up and DHCP completes, but no packets pass for several minutes until the modem drops the call (call_end_reason 3/type 3/verbose 2001, then verbose 55 on redial). A phone on the same cell works. Is this a known issue on this firmware, and is there a newer firmware or driver fix?

  3. Does this firmware send QMAP flow-control commands (FLOW_ENABLE/FLOW_DISABLE)? The driver’s handler was a //TODO. What host behaviour do you expect?

  4. After a channel reset through the driver’s debugfs mhi_netdev/…/reset, the modem stops completing UL transfers and sends no DL data until the call is redialled. Is a channel reset with the call still up supported, or does the data call (WDA data format / QMAP bind) have to be set up again?

I can provide logs (QXDM, mhimon, dmesg) if needed.

Thank you.

2

Hello, sadly I don’t have any answers but I’m wondering if you got any further on this?

Same modem and same version branch and seems to hold a little better on LTE only but will stall regarding streaming usually.

Thanks in advance.