【hns-0412】 add debugfs support for interrupt coalesce

[Fred Kimmy]

Bug Description]
When the interrupt adaptation function of Kunpeng 920 onboard network card is turned on, the currently effective tx-usecs and rx-usecs values cannot be queried.

[Steps to Reproduce]
1)ethtool -C ethx adaptive-rx on adaptive-tx on
2)send packets to ethx with iperf
3)query currently effective tx-usecs and rx-usecs values via debugfs
4)ping ethx
5)query currently effective tx-usecs and rx-usecs values via debugfs

[Actual Results]
no "coalesce_info" node in debugfs, step 3) and step 5) can not execute.

[Expected Results]
step 3) and step 5) can get information like：
cat /sys/kernel/debug/hns3/0000\:7d\:00.0/coalesce_info
tx interrupt coalesce info:
VEC_ID ALGO_STATE PROFILE_ID CQE_MODE TUNE_STATE STEPS_LEFT STEPS_RIGHT TIRED SW_GL SW_QL HW_GL HW_QL
0 START 0 EQE ON_TOP 0 0 0 20 0 10 NA
1 START 0 EQE ON_TOP 0 0 0 20 0 10 NA
rx interrupt coalesce info:
VEC_ID ALGO_STATE PROFILE_ID CQE_MODE TUNE_STATE STEPS_LEFT STEPS_RIGHT TIRED SW_GL SW_QL HW_GL HW_QL
0 START 0 EQE ON_TOP 0 0 0 20 0 10 NA
1 START 0 EQE ON_TOP 0 0 0 20 0 10 NA

[Reproducibility]
100%

[Additional information]
(Firmware version, kernel version, affected hardware, etc. if required):

Business functions are not affected, only DFX functions are affected。
OS: Ubuntu 20.04.3 LTS
kernel: 5.11.0-27-generic #29~20.04.1-Ubuntu SMP Wed Aug 11 15:58:08 UTC 2021 aarch64 aarch64 aarch64 GNU/Linux
hardware：kunpeng 920 onboard network card

[Resolution]
c99fead7cb07 net: hns3: add debugfs support for interrupt coalesce

[Ike Panhc (ikepanhc)]

Patch c99fead7cb07 ("net: hns3: add debugfs support for interrupt coalesce") has been merged into mainline kernel since v5.16.

However, this patch can not be cherry-picked cleanly to v5.4, v5.13 and v5.15 kernel but it might be possible to solve the conflict and backport to v5.15 kernel.

I will try to backport to v5.15 kernel and see if that would work.

[Ike Panhc (ikepanhc)]

For Ubuntu 5.15 kernel we also need to bring in b9860276f856 ("net: hns3: debugfs add support dumping page pool info") for dependency. There are too many new codes bringing-in and only for 1 debugfs file.

Unless there are problem fixed e.g. NIC resetting unexpected, performance dropping, packet loss, to cherry-pick patch c99fead7cb07 won't satisfy SRU policy.

Please let me know if patch c99fead7cb07 can fix any issue other then just shows values, or I will close this bug.