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01296b39d3
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:
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.