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Date: Mon, 27 May 2024 11:25:34 +0200
From: Stefan Lippers-Hollmann <s.l-h@gmx.de>
To: Ping-Ke Shih <pkshih@realtek.com>
Cc: Bitterblue Smith <rtl8821cerfe2@gmail.com>,
 "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>, Larry
 Finger <Larry.Finger@lwfinger.net>, Christian Hewitt <chewitt@libreelec.tv>
Subject: Re: [PATCH v7 12/12] wifi: rtlwifi: Enable the new rtl8192du driver
Message-ID: <20240527112534.4dbcdf75@mir>
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Hi

On 2024-05-27, Ping-Ke Shih wrote:
> Bitterblue Smith <rtl8821cerfe2@gmail.com> wrote:
> > The RTL8192DU is an older Wifi 4 dual band chip. It comes in two
> > flavours: single MAC single PHY (like most Realtek Wifi 4 USB devices)=
,
> > and dual MAC dual PHY.
[...]
> > Stefan Lippers-Hollmann tested the speed in the 5 GHz band with 40 MHz
> > channel width: 173/99 megabits/second.
>
> Could you please confirm this description is still correct in v7?
> If so, your Tested-by tag is welcome.

I held back with a formal Tested-by for this, as rtlwifi needs
some fixing after the chanctx changes
(0a44dfc070749514b804ccac0b1fd38718f7daa1, "wifi: mac80211:
simplify non-chanctx drivers") went in (for v6.9 and up).

So, yes, rtl8192du v7 itself works fine (as did v6 and previous), but
the chanctx changes do cause a performance regression, resulting in
lower (and very inconsistent) throughput and larger packet loss,
due to the rate control being confused. As Bitterblue found out,
rtlwifi relies on the previous behaviour imposed by

ieee80211_hw_config(local, ~0);

As a consequence of the change to

ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_LISTEN_INTERVAL |
				   IEEE80211_CONF_CHANGE_MONITOR |
				   IEEE80211_CONF_CHANGE_PS |
				   IEEE80211_CONF_CHANGE_RETRY_LIMITS |
				   IEEE80211_CONF_CHANGE_IDLE);

mac80211 effectively sets a retry limit of 0x4, while rtlwifi
expects a retry limit of 0x30 (in STA mode or 0x7 in AP mode),
causing rtlwifi not to settle on a good fallback rate (and thereby
losing packets).

Disclaimer: the above issue and its explanation has been discovered
by Bitterblue, I just did the git bisecting (rtl8192du on top of
v6.8..v6.9) and performance testing to pinpoint the commit causing
the regression.

rtl8192du on top of v6.9+ (with the chanctx changes):
$ iperf3 -c <remote_ipv6>
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec   384 KBytes  3.14 Mbits/sec
[  5]   1.00-2.00   sec   512 KBytes  4.19 Mbits/sec
[  5]   2.00-3.00   sec  1.00 MBytes  8.39 Mbits/sec
[  5]   3.00-4.00   sec   640 KBytes  5.24 Mbits/sec
[  5]   4.00-5.00   sec  0.00 Bytes  0.00 bits/sec
[  5]   5.00-6.00   sec  0.00 Bytes  0.00 bits/sec
[  5]   6.00-7.00   sec   256 KBytes  2.10 Mbits/sec
[  5]   7.00-8.00   sec   640 KBytes  5.25 Mbits/sec
[  5]   8.00-9.00   sec   512 KBytes  4.19 Mbits/sec
[  5]   9.00-10.00  sec   256 KBytes  2.10 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-10.00  sec  4.12 MBytes  3.46 Mbits/sec                  rece=
iver

$ iperf3 -c <remote_ipv6> --reverse
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  12.9 MBytes   108 Mbits/sec    0    629 KBytes
[  5]   1.00-2.00   sec  9.75 MBytes  81.8 Mbits/sec    0   1.13 MBytes
[  5]   2.00-3.00   sec  11.0 MBytes  92.3 Mbits/sec    0   1.63 MBytes
[  5]   3.00-4.00   sec  1.38 MBytes  11.5 Mbits/sec    1   1.67 MBytes
[  5]   4.00-5.00   sec  0.00 Bytes  0.00 bits/sec    1   1.39 KBytes
[  5]   5.00-6.00   sec  0.00 Bytes  0.00 bits/sec    1   1.39 KBytes
[  5]   6.00-7.00   sec  0.00 Bytes  0.00 bits/sec    0   1.39 KBytes
[  5]   7.00-8.00   sec  9.88 MBytes  82.8 Mbits/sec    0   2.12 MBytes
[  5]   8.00-9.00   sec  6.88 MBytes  57.7 Mbits/sec    3   2.32 MBytes
[  5]   9.00-10.00  sec  0.00 Bytes  0.00 bits/sec    0   2.32 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  51.8 MBytes  43.4 Mbits/sec    6             send=
er

$ iperf3 -c <remote_ipv6> --bidir
[ ID][Role] Interval           Transfer     Bitrate         Retr  Cwnd
[  5][RX-S]   0.00-1.00   sec  0.00 Bytes  0.00 bits/sec
[  8][TX-S]   0.00-1.00   sec  1.38 MBytes  11.5 Mbits/sec    0   90.6 KBy=
tes
[  5][RX-S]   1.00-2.00   sec  0.00 Bytes  0.00 bits/sec
[  8][TX-S]   1.00-2.00   sec  4.12 MBytes  34.6 Mbits/sec    4   1.39 KBy=
tes
[  5][RX-S]   2.00-3.00   sec  0.00 Bytes  0.00 bits/sec
[  8][TX-S]   2.00-3.00   sec  0.00 Bytes  0.00 bits/sec    1   1.39 KByte=
s
[  5][RX-S]   3.00-4.00   sec  0.00 Bytes  0.00 bits/sec
[  8][TX-S]   3.00-4.00   sec  0.00 Bytes  0.00 bits/sec    1   1.39 KByte=
s
[  5][RX-S]   4.00-5.00   sec  0.00 Bytes  0.00 bits/sec
[  8][TX-S]   4.00-5.00   sec  0.00 Bytes  0.00 bits/sec    0   1.39 KByte=
s
[  5][RX-S]   5.00-6.00   sec  0.00 Bytes  0.00 bits/sec
[  8][TX-S]   5.00-6.00   sec  0.00 Bytes  0.00 bits/sec    2    106 KByte=
s
[  5][RX-S]   6.00-7.00   sec  0.00 Bytes  0.00 bits/sec
[  8][TX-S]   6.00-7.00   sec  0.00 Bytes  0.00 bits/sec    0    106 KByte=
s
[  5][RX-S]   7.00-8.00   sec  0.00 Bytes  0.00 bits/sec
[  8][TX-S]   7.00-8.00   sec  0.00 Bytes  0.00 bits/sec    0    106 KByte=
s
[  5][RX-S]   8.00-9.00   sec  0.00 Bytes  0.00 bits/sec
[  8][TX-S]   8.00-9.00   sec  0.00 Bytes  0.00 bits/sec    0    106 KByte=
s
[  5][RX-S]   9.00-10.00  sec  0.00 Bytes  0.00 bits/sec
[  8][TX-S]   9.00-10.00  sec  1.25 MBytes  10.5 Mbits/sec    2    119 KBy=
tes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID][Role] Interval           Transfer     Bitrate         Retr
[  5][RX-S]   0.00-10.01  sec  0.00 Bytes  0.00 bits/sec                  =
receiver
[  8][TX-S]   0.00-10.01  sec  6.75 MBytes  5.66 Mbits/sec   10           =
  sender

Again, rtl8192du v7 itself is 'fine' and could (can) achieve 180/100
MBit/s before the chanctx changes, so merging v7 might be okay - but
there needs to be a fix for rtlwifi as a whole (and maybe even other
drivers) for v6.9+ and the chanctx changes that came with it (not
every chipset supported by rtlwifi might be affected equally badly,
e.g. rtl8192cu might not noticeably be, according to Bitterblue's
testing).

So with the (performance/ packet loss) caveat above:

Tested-by: Stefan Lippers-Hollmann <s.l-h@gmx.de>

I am running rtl8192du v7 on top of v6.9.2 now (and tested it on top
of wireless-next as of last Friday (2024-05-24)), with the performance
figures above.

Regards
	Stefan Lippers-Hollmann

=2D-
This is the result of my git bisecting:

$ git bisect good
0a44dfc070749514b804ccac0b1fd38718f7daa1 is the first bad commit
commit 0a44dfc070749514b804ccac0b1fd38718f7daa1
Author: Johannes Berg <johannes.berg@intel.com>
Date:   Mon Jan 29 19:34:38 2024 +0100

    wifi: mac80211: simplify non-chanctx drivers

    There are still surprisingly many non-chanctx drivers, but in
    mac80211 that code is a bit awkward. Simplify this by having
    those drivers assign 'emulated' ops, so that the mac80211 code
    can be more unified between non-chanctx/chanctx drivers. This
    cuts the number of places caring about it by about 15, which
    are scattered across - now they're fewer and no longer in the
    channel context handling.

    Link: https://msgid.link/20240129194108.6d0ead50f5cf.I60d093b2fc81ca18=
53925a4d0ac3a2337d5baa5b@changeid
    Signed-off-by: Johannes Berg <johannes.berg@intel.com>

 drivers/net/wireless/admtek/adm8211.c                          |   4 +
 drivers/net/wireless/ath/ar5523/ar5523.c                       |   4 +
 drivers/net/wireless/ath/ath5k/mac80211-ops.c                  |   4 +
 drivers/net/wireless/ath/ath9k/htc_drv_main.c                  |   4 +
 drivers/net/wireless/ath/ath9k/main.c                          |   4 +
 drivers/net/wireless/ath/carl9170/main.c                       |   4 +
 drivers/net/wireless/ath/wcn36xx/main.c                        |   4 +
 drivers/net/wireless/atmel/at76c50x-usb.c                      |   4 +
 drivers/net/wireless/broadcom/b43/main.c                       |   4 +
 drivers/net/wireless/broadcom/b43legacy/main.c                 |   4 +
 drivers/net/wireless/broadcom/brcm80211/brcmsmac/mac80211_if.c |   4 +
 drivers/net/wireless/intel/iwlegacy/3945-mac.c                 |   4 +
 drivers/net/wireless/intel/iwlegacy/4965-mac.c                 |   4 +
 drivers/net/wireless/intel/iwlwifi/dvm/mac80211.c              |   4 +
 drivers/net/wireless/intersil/p54/main.c                       |   4 +
 drivers/net/wireless/marvell/libertas_tf/main.c                |   4 +
 drivers/net/wireless/marvell/mwl8k.c                           |   4 +
 drivers/net/wireless/mediatek/mt76/mt7603/main.c               |   4 +
 drivers/net/wireless/mediatek/mt76/mt76x0/pci.c                |   4 +
 drivers/net/wireless/mediatek/mt76/mt76x0/usb.c                |   4 +
 drivers/net/wireless/mediatek/mt76/mt76x2/pci_main.c           |   4 +
 drivers/net/wireless/mediatek/mt76/mt76x2/usb_main.c           |   4 +
 drivers/net/wireless/mediatek/mt76/mt792x_core.c               |   7 +-
 drivers/net/wireless/mediatek/mt76/mt7996/main.c               |   4 +
 drivers/net/wireless/mediatek/mt7601u/main.c                   |   4 +
 drivers/net/wireless/purelifi/plfxlc/mac.c                     |   4 +
 drivers/net/wireless/ralink/rt2x00/rt2400pci.c                 |   4 +
 drivers/net/wireless/ralink/rt2x00/rt2500pci.c                 |   4 +
 drivers/net/wireless/ralink/rt2x00/rt2500usb.c                 |   4 +
 drivers/net/wireless/ralink/rt2x00/rt2800pci.c                 |   4 +
 drivers/net/wireless/ralink/rt2x00/rt2800soc.c                 |   4 +
 drivers/net/wireless/ralink/rt2x00/rt2800usb.c                 |   4 +
 drivers/net/wireless/ralink/rt2x00/rt61pci.c                   |   4 +
 drivers/net/wireless/ralink/rt2x00/rt73usb.c                   |   4 +
 drivers/net/wireless/realtek/rtl818x/rtl8180/dev.c             |   4 +
 drivers/net/wireless/realtek/rtl818x/rtl8187/dev.c             |   4 +
 drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c          |   4 +
 drivers/net/wireless/realtek/rtlwifi/core.c                    |   4 +
 drivers/net/wireless/realtek/rtw88/mac80211.c                  |   4 +
 drivers/net/wireless/realtek/rtw89/core.c                      |   7 +-
 drivers/net/wireless/rsi/rsi_91x_mac80211.c                    |   4 +
 drivers/net/wireless/st/cw1200/main.c                          |   4 +
 drivers/net/wireless/ti/wl1251/main.c                          |   4 +
 drivers/net/wireless/virtual/mac80211_hwsim.c                  |   4 +
 drivers/net/wireless/zydas/zd1211rw/zd_mac.c                   |   4 +
 drivers/staging/vt6655/device_main.c                           |   4 +
 drivers/staging/vt6656/main_usb.c                              |   4 +
 include/net/mac80211.h                                         |  13 ++
 net/mac80211/cfg.c                                             |  42 +++-=
---
 net/mac80211/chan.c                                            | 111 +++-=
-------------
 net/mac80211/ieee80211_i.h                                     |   9 +-
 net/mac80211/iface.c                                           |   6 +-
 net/mac80211/main.c                                            | 205 ++++=
+++++++++++++++++++++------
 net/mac80211/mlme.c                                            |   3 +-
 net/mac80211/offchannel.c                                      |  21 ++--
 net/mac80211/scan.c                                            |  18 +--
 net/mac80211/tx.c                                              |   2 -
 net/mac80211/util.c                                            |  27 ++--
 58 files changed, 444 insertions(+), 207 deletions(-)

$ git bisect log
git bisect start
# Status: warte auf guten und schlechten Commit
# bad: [a38297e3fb012ddfa7ce0321a7e5a8daeb1872b6] Linux 6.9
git bisect bad a38297e3fb012ddfa7ce0321a7e5a8daeb1872b6
# Status: warte auf gute(n) Commit(s), schlechter Commit bekannt
# good: [e8f897f4afef0031fe618a8e94127a0934896aba] Linux 6.8
git bisect good e8f897f4afef0031fe618a8e94127a0934896aba
# bad: [480e035fc4c714fb5536e64ab9db04fedc89e910] Merge tag 'drm-next-2024=
-03-13' of https://gitlab.freedesktop.org/drm/kernel
git bisect bad 480e035fc4c714fb5536e64ab9db04fedc89e910
# bad: [9187210eee7d87eea37b45ea93454a88681894a4] Merge tag 'net-next-6.9'=
 of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
git bisect bad 9187210eee7d87eea37b45ea93454a88681894a4
# bad: [9187210eee7d87eea37b45ea93454a88681894a4] Merge tag 'net-next-6.9'=
 of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
git bisect bad 9187210eee7d87eea37b45ea93454a88681894a4
# good: [a01c9fe32378636ae65bec8047b5de3fdb2ba5c8] Merge tag 'nfsd-6.9' of=
 git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux
git bisect good a01c9fe32378636ae65bec8047b5de3fdb2ba5c8
# bad: [ca61ba3885274a684c83d8a538eb77b30e38ee92] Merge branch 'rework-gen=
et-mdioclocking'
git bisect bad ca61ba3885274a684c83d8a538eb77b30e38ee92
# good: [f42822f22b1c5f72c7e3497d9683f379ab0c5fe4] bnxt_en: Use firmware p=
rovided maximum filter counts.
git bisect good f42822f22b1c5f72c7e3497d9683f379ab0c5fe4
# bad: [e10cd2ddd89e8b3e61b49247067e79f7debec2f1] wifi: rtw89: load BB par=
ameters to PHY-1
git bisect bad e10cd2ddd89e8b3e61b49247067e79f7debec2f1
# good: [2594e4d9e1a2d79bf7bb262974abaf5ef153e371] wifi: iwlwifi: prepare =
for reading SAR tables from UEFI
git bisect good 2594e4d9e1a2d79bf7bb262974abaf5ef153e371
# bad: [719036ae06d4bfdb65139e3947a8404dec298bc5] wifi: cfg80211: move pun=
cturing validation code
git bisect bad 719036ae06d4bfdb65139e3947a8404dec298bc5
# good: [1209f487d452ff7e822dec30661fd6b5163fb8cf] wifi: rtl8xxxu: Add TP-=
Link TL-WN823N V2
git bisect good 1209f487d452ff7e822dec30661fd6b5163fb8cf
# good: [4dbd964f33aab6f99891b9610ad4b36cc215be0d] wifi: rtw89: 8922a: add=
 chip_ops::rfk_hw_init
git bisect good 4dbd964f33aab6f99891b9610ad4b36cc215be0d
# good: [2fd53eb04c492eb9a2b06f994b36e5cf34ba7541] wifi: mac80211: remove =
unused MAX_MSG_LEN define
git bisect good 2fd53eb04c492eb9a2b06f994b36e5cf34ba7541
# bad: [0a44dfc070749514b804ccac0b1fd38718f7daa1] wifi: mac80211: simplify=
 non-chanctx drivers
git bisect bad 0a44dfc070749514b804ccac0b1fd38718f7daa1
# good: [61f0261131c8dc2beeb6b34781a54788221081e9] wifi: mac80211: clean u=
p band switch in duration
git bisect good 61f0261131c8dc2beeb6b34781a54788221081e9
# good: [2d9698dd32d086e47b8bff3df4322cc017c17b55] wifi: mac80211: clean u=
p HE 6 GHz and EHT chandef parsing
git bisect good 2d9698dd32d086e47b8bff3df4322cc017c17b55
# first bad commit: [0a44dfc070749514b804ccac0b1fd38718f7daa1] wifi: mac80=
211: simplify non-chanctx drivers