Fwd: 5c8a79e8e12b ("wifi: rtw88: correct PS calculation for SUPPORTS_DYNAMIC_PS", 2023-05-27) increases CPU usage usage for irq

[Bagas Sanjaya]

Hi,

I notice a regression report on Bugzilla [1]. Quoting from it:

> This commit improves power saving - it enables the kernel to achieve package C8. To achieve package C8, 3 Ubuntu VMD commits must be applied as well. The combined patch for the 3 Ubuntu VMD commits is attached (just in case). Package C8 lowers power usage on the laptop from 5.6W to 2.6W.
> 
> However, a side-effect of this commit is that CPU usage for irq/155-rtw88_pci has increased noticeably. This commit was introduced in 6.4-rc6. To confirm this commit is the cause, a branch was created from 6.4-rc5. This commit and the 3 Ubuntu VMD commits were applied. The resulting kernel was built and tested - it can achieve package C8 and exhibits the increased CPU usage on irq/155-rtw88_pci.
> 
> Booting and running top for 30 min with the system otherwise idle, gives these results for CPU on irq/155-rtw88_pci:
> 6.4-rc5     - 00:02.9, mostly   0% and 0.3% displayed
> patched rc5 - 00:13.4, mostly 0.7% and 1.0% displayed
> By comparison, an 8th Gen Dell with an Intel WIFI has CPU usage of 00:01.7 under the same conditions.
> 
> Laptop is a HP 15s-fq4011TU 11th Gen (Tiger Lake) Intel with (from lspci) Realtek Semiconductor Co., Ltd. RTL8822CE 802.11ac PCIe Wireless Network Adapter and Intel Corporation Volume Management Device NVMe RAID Controller.
> 
> Ubuntu bug https://bugs.launchpad.net/ubuntu/+source/linux-hwe-6.2/+bug/2025040 provides further background.
> 
> Please advise if I can assist with further testing.

See Bugzilla for the full thread and attached proposed patch(es) that fix
this regression.

Anyway, I'm adding this regression to be tracked by regzbot:

#regzbot introduced: 26a125f550a3bf https://bugzilla.kernel.org/show_bug.cgi?id=217828
#regzbot title: correcting SUPPORTS_DYNAMIC_PS calculation for rtw88 increases CPU utilization
#regzbot link: https://bugs.launchpad.net/ubuntu/+source/linux-hwe-6.2/+bug/2025040

Thanks.

[1]: https://bugzilla.kernel.org/show_bug.cgi?id=217828

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