WCN6855 service timeout issues

[Kristian Evensen]

Hello,

I am trying to make a WCN6855-based card work with on an x86-device
running kernel 5.15. My base system is OpenWRT (compiled from master
today) + backports-5.15-33. As WCN6855 is not support by kernel 5.15,
I have backported all ath11k commits up to 3926e0c122 ("ath11k: Fix
warnings reported by checkpatch"), and brought mhi in sync with
mhi-next (13b9b814da) and qrtr in sync with net-next (f4b41f062c).

When I boot my device, the card is detect and board file found, but
communication times out almost immediately. In my kernel log, I see
the following:

[   11.336010] ath11k_pci 0000:06:00.0: BAR 0: assigned [mem
0x91000000-0x911fffff 64bit]
[   11.344336] ath11k_pci 0000:06:00.0: MSI vectors: 1
[   11.350532] ath11k_pci 0000:06:00.0: wcn6855 hw2.1
[   11.513448] mhi mhi0: Requested to power ON
[   11.517895] mhi mhi0: Power on setup success
[   11.904189] mhi mhi0: Wait for device to enter SBL or Mission mode
[   12.551007] ath11k_pci 0000:06:00.0: chip_id 0x12 chip_family 0xb
board_id 0xff soc_id 0x400c1211
[   12.560045] ath11k_pci 0000:06:00.0: fw_version 0x11090c35
fw_build_timestamp 2022-04-18 20:23 fw_build_id
WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.9
[   12.768324] ath11k_pci 0000:06:00.0: leaving PCI ASPM disabled to
avoid MHI M2 problems
[   13.814188] ath11k_pci 0000:06:00.0: failed to receive control
response completion, polling..
[   14.844167] ath11k_pci 0000:06:00.0: Service connect timeout
[   14.849919] ath11k_pci 0000:06:00.0: failed to connect to HTT: -110
[   14.858741] ath11k_pci 0000:06:00.0: failed to start core: -110
[   15.074355] ath11k_pci 0000:06:00.0: ignore reset dev flags 0x4000
[   25.332283] ath11k_pci 0000:06:00.0: failed to wait wlan mode
request (mode 4): -110
[   25.340294] ath11k_pci 0000:06:00.0: qmi failed to send wlan mode off: -110

The device and PCI-slot should be good. I inserted another wifi-card
that uses the ath10k-driver and it works fine (and without the " ..
polling.." message). Also, the WCN6855-card works well when I install
Ubuntu on the same device + kernel 5.17 + board file. The board file
is supplied by the vendor, but as it works fine with ath11k from the
5.17 kernel I guess it is ok.

In order to try to make progress, I searched for the different error
messages and got quite a lot of ath10k-related hits on the first ones
(".. polling .." and "Service connect timeout"). However, for example
disabling MSI or enabling PCI quirks had no effect on my device.

Does anyone know what could be wrong or have an idea of where I should look?

Thanks in advance for any help,
Kristian