On 3/9/2024 3:31 AM, Baochen Qiang wrote:
> Currently we force enable power save on non-running vdevs, this results
> in unexpected ping latency in below scenarios:
> 1. disable power save from userspace.
> 2. trigger suspend/resume.
>
> With step 1 power save is disabled successfully and we get a good latency:
>
> PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
> 64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=5.13 ms
> 64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=5.45 ms
> 64 bytes from 192.168.1.1: icmp_seq=3 ttl=64 time=5.99 ms
> 64 bytes from 192.168.1.1: icmp_seq=4 ttl=64 time=6.34 ms
> 64 bytes from 192.168.1.1: icmp_seq=5 ttl=64 time=4.47 ms
> 64 bytes from 192.168.1.1: icmp_seq=6 ttl=64 time=6.45 ms
>
> While after step 2, the latency becomes much larger:
>
> PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
> 64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=17.7 ms
> 64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=15.0 ms
> 64 bytes from 192.168.1.1: icmp_seq=3 ttl=64 time=14.3 ms
> 64 bytes from 192.168.1.1: icmp_seq=4 ttl=64 time=16.5 ms
> 64 bytes from 192.168.1.1: icmp_seq=5 ttl=64 time=20.1 ms
>
> The reason is, with step 2, power save is force enabled due to vdev not
> running, although mac80211 was trying to disable it to honor userspace
> configuration:
>
> ath11k_pci 0000:03:00.0: wmi cmd sta powersave mode psmode 1 vdev id 0
> Call Trace:
> ath11k_wmi_pdev_set_ps_mode
> ath11k_mac_op_bss_info_changed
> ieee80211_bss_info_change_notify
> ieee80211_reconfig
> ieee80211_resume
> wiphy_resume
>
> This logic is taken from ath10k where it was added due to below comment:
>
> Firmware doesn't behave nicely and consumes more power than
> necessary if PS is disabled on a non-started vdev.
>
> However we don't know whether such an issue also occurs to ath11k firmware
> or not. But even if it does, it's not appropriate because it goes against
> userspace, even cfg/mac80211 don't know we have enabled it in fact.
>
> Remove it to fix this issue. In this way we not only get a better latency,
> but also, and the most important, keeps the consistency between userspace
> and kernel/driver. The biggest price for that would be the power consumption,
> which is not that important, compared with the consistency.
>
> Tested-on: WCN6855 hw2.0 PCI WLAN.HSP.1.1-03125-QCAHSPSWPL_V1_V2_SILICONZ_LITE-3.6510.30
>
> Fixes: b2beffa7d9a6 ("ath11k: enable 802.11 power save mode in station mode")
> Signed-off-by: Baochen Qiang <quic_bqiang@xxxxxxxxxxx>
Acked-by: Jeff Johnson <quic_jjohnson@xxxxxxxxxxx>
