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Thu, 23 Apr 2026 12:34:44 -0700 (PDT) Message-ID: Date: Thu, 23 Apr 2026 22:34:42 +0300 Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH rtw-next v2 5/5] wifi: rtl8xxxu: Enable 40 MHz width by default To: Linux regressions mailing list , "linux-wireless@vger.kernel.org" Cc: Ping-Ke Shih , Jes Sorensen , art1310@proton.me References: <4f053103-adfd-4ead-acb3-ef69127a4bab@gmail.com> <8a4c664f-231f-437e-b010-b741c7ed7be8@leemhuis.info> Content-Language: en-US From: Bitterblue Smith In-Reply-To: <8a4c664f-231f-437e-b010-b741c7ed7be8@leemhuis.info> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 23/04/2026 16:39, Linux regression tracking (Thorsten Leemhuis) wrote: > On 11/20/25 15:13, Bitterblue Smith wrote: >> 40 MHz support is hidden behind the ht40_2g module parameter with >> this comment: >> >> /* >> * Some APs will negotiate HT20_40 in a noisy environment leading >> * to miserable performance. Rather than defaulting to this, only >> * enable it if explicitly requested at module load time. >> */ > > FYI: this patch causes a regression that was reported to bugzilla > (reporter CCed here): https://bugzilla.kernel.org/show_bug.cgi?id=221394 > Hi Thorsten, Thanks for letting us know. I replied at the Bugzilla. > """ > Since kernel 6.19.0, the rtl8xxxu driver fails to maintain a connection > with the Realtek RTL8188FTV (0bda:f179) USB Wi-Fi adapter. The device > gets stuck "configuring interface" and eventually times out, effectively > disappearing from the network manager. > > Regression Window: > Works perfectly on: 6.12.x (LTS) and 6.18.x (LTS and non LTS). > Broken on: 6.19.x, up through 7.0.0. > > Notes: > - The device remains visible on the USB bus (lsusb still shows 0bda:f179). > - The wlan0 interface is created. > - NetworkManager attempts to associate, but authentication times out. > - Disabling USB autosuspend (usbcore.autosuspend=-1) does not resolve > the issue. > > Hardware: > Bus 001 Device 002: ID 0bda:f179 Realtek Semiconductor Corp. RTL8188FTV > 802.11b/g/n 1T1R 2.4G WLAN Adapter > """ > > Then later: > > """ > I confirmed that the Commit dbf9b7b "wifi: rtl8xxxu: Enable 40 MHz width > by default" is the cause of the regression. > > I tested passing cfg80211_disable_40mhz_24ghz=1 to the cfg80211 module > on 6.19.x and 7.0, and the adapter works perfectly again. > > In Windows, forcing the adapter to 20_40MHz causes it to be unable to > connect to any AP, and it only works in 20MHz mode. In Linux 6.19+, it > gets stuck configuring the interface and crashes. So this is most > probably a hardware issue. > """ > > Ciao, Thorsten > >> This parameter was added in commit 26f1fad29ad9 ("New driver: >> rtl8xxxu (mac80211)"). Back then rtl8xxxu only supported RTL8723AU >> and the RTL8192CU family. It's entirely possible the miserable >> performance was due to mistakes in the channel switching function, >> which were fixed in a previous patch. >> >> Delete the ht40_2g module parameter. If someone still needs to >> disable 40 MHz support, cfg80211 has the module parameter >> cfg80211_disable_40mhz_24ghz. That works too. >> >> Signed-off-by: Bitterblue Smith >> Reviewed-by: Ping-Ke Shih >> --- >> v2: >> - Add Reviewed-by. >> --- >> drivers/net/wireless/realtek/rtl8xxxu/core.c | 19 ++++--------------- >> 1 file changed, 4 insertions(+), 15 deletions(-) >> >> diff --git a/drivers/net/wireless/realtek/rtl8xxxu/core.c b/drivers/net/wireless/realtek/rtl8xxxu/core.c >> index a18f73aea837..c06ad064f37c 100644 >> --- a/drivers/net/wireless/realtek/rtl8xxxu/core.c >> +++ b/drivers/net/wireless/realtek/rtl8xxxu/core.c >> @@ -20,7 +20,6 @@ >> #define DRIVER_NAME "rtl8xxxu" >> >> int rtl8xxxu_debug; >> -static bool rtl8xxxu_ht40_2g; >> static bool rtl8xxxu_dma_aggregation; >> static int rtl8xxxu_dma_agg_timeout = -1; >> static int rtl8xxxu_dma_agg_pages = -1; >> @@ -45,8 +44,6 @@ MODULE_FIRMWARE("rtlwifi/rtl8192fufw.bin"); >> >> module_param_named(debug, rtl8xxxu_debug, int, 0600); >> MODULE_PARM_DESC(debug, "Set debug mask"); >> -module_param_named(ht40_2g, rtl8xxxu_ht40_2g, bool, 0600); >> -MODULE_PARM_DESC(ht40_2g, "Enable HT40 support on the 2.4GHz band"); >> module_param_named(dma_aggregation, rtl8xxxu_dma_aggregation, bool, 0600); >> MODULE_PARM_DESC(dma_aggregation, "Enable DMA packet aggregation"); >> module_param_named(dma_agg_timeout, rtl8xxxu_dma_agg_timeout, int, 0600); >> @@ -4896,8 +4893,7 @@ rtl8xxxu_bss_info_changed(struct ieee80211_hw *hw, struct ieee80211_vif *vif, >> sgi = 1; >> >> highest_rate = fls(ramask) - 1; >> - if (rtl8xxxu_ht40_2g && >> - (sta->deflink.ht_cap.cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40)) >> + if (sta->deflink.ht_cap.cap & IEEE80211_HT_CAP_SUP_WIDTH_20_40) >> bw = RATE_INFO_BW_40; >> else >> bw = RATE_INFO_BW_20; >> @@ -7851,7 +7847,8 @@ static int rtl8xxxu_probe(struct usb_interface *interface, >> sband->ht_cap.ht_supported = true; >> sband->ht_cap.ampdu_factor = IEEE80211_HT_MAX_AMPDU_64K; >> sband->ht_cap.ampdu_density = IEEE80211_HT_MPDU_DENSITY_16; >> - sband->ht_cap.cap = IEEE80211_HT_CAP_SGI_20 | IEEE80211_HT_CAP_SGI_40; >> + sband->ht_cap.cap = IEEE80211_HT_CAP_SGI_20 | IEEE80211_HT_CAP_SGI_40 | >> + IEEE80211_HT_CAP_SUP_WIDTH_20_40; >> memset(&sband->ht_cap.mcs, 0, sizeof(sband->ht_cap.mcs)); >> sband->ht_cap.mcs.rx_mask[0] = 0xff; >> sband->ht_cap.mcs.rx_mask[4] = 0x01; >> @@ -7860,15 +7857,7 @@ static int rtl8xxxu_probe(struct usb_interface *interface, >> sband->ht_cap.cap |= IEEE80211_HT_CAP_SGI_40; >> } >> sband->ht_cap.mcs.tx_params = IEEE80211_HT_MCS_TX_DEFINED; >> - /* >> - * Some APs will negotiate HT20_40 in a noisy environment leading >> - * to miserable performance. Rather than defaulting to this, only >> - * enable it if explicitly requested at module load time. >> - */ >> - if (rtl8xxxu_ht40_2g) { >> - dev_info(&udev->dev, "Enabling HT_20_40 on the 2.4GHz band\n"); >> - sband->ht_cap.cap |= IEEE80211_HT_CAP_SUP_WIDTH_20_40; >> - } >> + >> hw->wiphy->bands[NL80211_BAND_2GHZ] = sband; >> >> hw->wiphy->rts_threshold = 2347; > > #regzbot introduced: dbf9b7b > #regzbot title: wifi: rtl8xxxu: 40 MHz mode breaks things (just like in > Windows) > #regzbot dup: https://bugzilla.kernel.org/show_bug.cgi?id=221394