Re: Problems with rtw89 on 5Ghz wlans.

[Bitterblue Smith <rtl8821cerfe2@gmail.com>]

On 30/09/2026 12:21, PierluigiFrullani wrote:
> Hello all,
>     I'm using Linux Mint 22.1 with kernel 7.0.0-34-generic and a 
> 02:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8852BE PCIe 802.11ax Wireless Network Controller [1T1R] [10ec:b85b] 
> that has lot of issues with the 5Ghz wlan.
> The problem is that has a very low sensitivity and can detect, in linux, these wlans only when I'm a few feet from access point.
> 
> 
> I've then swapped the driver with https://github.com/morrownr/rtw89 and found the same behaviour.
> I've then opened an issue there :
>  https://github.com/morrownr/rtw89/issues/128 and the peoples there managed to find the culprit and patch his driver that now works perfectly.
> For my understanding the problem was that my card ( may card model ? ) ( rfe_type 41 ) has only one antenna and is not correctly selected b y the driver.
> 
> Looking into the https://github.com/pkshih/rtw/blob/rtw-next/drivers/net/wireless/realtek/rtw89  code I can see that is really similar so then patche applied in the morrownr could possibly apply  also to the vanilla kernel driver.
> 
> 
> Patch is rather easy and with this patch allied and this driver loaded now the 5Ghz is perfectly working.
> 
> 
> Would you be interessed in pushing this patch also here ?
> 
> 
> In case, this is the patch ( also with the comments to verify that the driver loaded is the one that is patched ) :
> diff --git a/drivers/net/wireless/realtek/rtw89/mac.c b/drivers/net/wireless/realtek/rtw89/mac.c
> index df396fbfca26..81a4be7a593d 100644
> --- a/drivers/net/wireless/realtek/rtw89/mac.c
> +++ b/drivers/net/wireless/realtek/rtw89/mac.c
> @@ -3244,6 +3244,14 @@ static int rtw89_mac_setup_phycap_part0(struct rtw89_dev *rtwdev)
>      tx_ant = u32_get_bits(phycap->w3, RTW89_C2HREG_PHYCAP_W3_ANT_TX_NUM);
>      rx_ant = u32_get_bits(phycap->w3, RTW89_C2HREG_PHYCAP_W3_ANT_RX_NUM);
>  
> +    if (chip->chip_id == RTL8852B && efuse->rfe_type == 41 &&
> +        tx_nss == 1 && tx_ant == 2 && rx_nss == 1 && rx_ant == 2) {
> +        tx_ant = 1;
> +        rx_ant = 1;
> +
> +        rtw89_warn(rtwdev, "fix more stuff for RFE 41\n");
> +    }
> +
>      hal->tx_nss = tx_nss ? min_t(u8, tx_nss, chip->tx_nss) : chip->tx_nss;
>      hal->rx_nss = rx_nss ? min_t(u8, rx_nss, chip->rx_nss) : chip->rx_nss;
>  
> diff --git a/drivers/net/wireless/realtek/rtw89/rtw8852b.c b/drivers/net/wireless/realtek/rtw89/rtw8852b.c
> index 356623341f65..c9ee3c76cfc9 100644
> --- a/drivers/net/wireless/realtek/rtw89/rtw8852b.c
> +++ b/drivers/net/wireless/realtek/rtw89/rtw8852b.c
> @@ -771,6 +771,15 @@ static void rtw8852b_btc_set_rfe(struct rtw89_dev *rtwdev)
>      } else {
>          md->ant.type = BTC_ANT_SHARED;
>          md->bt0_pos = BTC_BT_BTG;
> +
> +        if (md->rfe_type == 41) {
> +            md->ant.num = 1;
> +            md->ant.single_pos = RF_PATH_B;
> +            md->ant.btg_pos = RF_PATH_B;
> +            md->ant.stream_cnt = 1;
> +
> +            rtw89_warn(rtwdev, "fix stuff for RFE 41\n");
> +        }
>      }
>      rtwdev->btc.btg_pos = md->ant.btg_pos;
>      rtwdev->btc.ant_type = md->ant.type;
> 
> 
> 
> All credits must absolutelly go to  dubhater (   https://github.com/dubhater ) that did all troubleshooting and wrote the patch.
>  
> My interest in this is only to have a (vanilla) kernel version of this driver that works correctly as lot of problems are reported by peoples using the same chip.
> 
> 
> 
> Thanks
> 
> 
> Pierluigi 

Hi,

Two other people reported the same problem recently. I decided to wait
for them to say if the patch helps or not. But I will send the patch
anyway next week.