On Monday, 29 November 2021 11:13:09 CET Wen Gong wrote:
> Currently mac80211 will send 3 scan request for each scan of WCN6855,
> they are 2.4 GHz/5 GHz/6 GHz band scan. Firmware of WCN6855 will
> cache the RNR IE(Reduced Neighbor Report element) which exist in the
> beacon of 2.4 GHz/5 GHz of the AP which is co-located with 6 GHz,
> and then use the cache to scan in 6 GHz band scan if the 6 GHz scan
> is in the same scan with the 2.4 GHz/5 GHz band, this will helpful to
> search more AP of 6 GHz. Also it will decrease the time cost of scan
> because firmware will use dual-band scan for the 2.4 GHz/5 GHz, it
> means the 2.4 GHz and 5 GHz scans are doing simultaneously.
> 
> Set the flag IEEE80211_HW_SINGLE_SCAN_ON_ALL_BANDS for WCN6855 since
> it supports 2.4 GHz/5 GHz/6 GHz and it is single pdev which means
> all the 2.4 GHz/5 GHz/6 GHz exist in the same wiphy/ieee80211_hw.
> 
> Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-01720.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1

I've tested this on ath-next on commit a93789ae541c ("ath11k: Avoid NULL ptr 
access during mgmt tx cleanup") with a WCN6856 card (EmWicon/jjplus WMX7205) 
with firmware WLAN.HSP.1.1-02892.1-QCAHSPSWPL_V1_V2_SILICONZ_LITE-1. ath-next 
was required for me because 32 MSI vectors are not available on the 
used system.

Without this patch, it works fine. With patch, I just have to connect to an AP 
via wpa_supplicant to crash the system. See the attached x86-64 .config, the 
stacktrace and the decoded stacktrace.

Kind regards,
	Sven