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Hermes SMTP Server) with ESMTPA ID 5a4e7a00ae694a37e2ae64cb3faaf16e; Fri, 11 Sep 2026 10:09:05 +0000 (UTC) From: not-eexto To: pkshih@realtek.com Cc: linux-wireless@vger.kernel.org, not-eexto Subject: [PATCH] wifi: rtw88: 8821c: Add HP single-antenna quirk Date: Fri, 11 Sep 2026 12:09:04 +0200 Message-ID: <20260911100904.50320-1-eexto@aol.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit References: <20260911100904.50320-1-eexto.ref@aol.com> Certain HP laptop platforms with RTL8821CE (PCI ID 10ec:c821, subsystem 103c:831a) are manufactured with only a single physical antenna wire connected to the Aux/S1 port (Port 2). As documented in the OEM Windows INF file (netrtwlane.inf): "single ant(connect to right one S1)" However, the eFuse on these chipsets reports RFE Type 2 (Main antenna, Port 1), causing the hardware SPDT RF switch to route to an unconnected port under Linux. This leads to severe signal attenuation (~ -86 dBm) and frequent beacon-loss disconnections. Add an automatic quirk in rtw8821c_read_efuse() for HP subsystem 10ec:c821 [103c:831a] that overrides efuse->rfe_option and efuse->rfe_option_full to 4 (Aux), routing the RF path to the physically connected antenna. Signed-off-by: not-eexto --- rtw8821c.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/net/wireless/realtek/rtw88/rtw8821c.c b/drivers/net/wireless/realtek/rtw88/rtw8821c.c index 9f0964d..32c7de5 100644 --- a/drivers/net/wireless/realtek/rtw88/rtw8821c.c +++ b/drivers/net/wireless/realtek/rtw88/rtw8821c.c @@ -15,6 +15,9 @@ #include "debug.h" #include "bf.h" #include "regd.h" +#if IS_ENABLED(CONFIG_PCI) +#include +#endif static const s8 lna_gain_table_0[8] = {22, 8, -6, -22, -31, -40, -46, -52}; static const s8 lna_gain_table_1[16] = {10, 6, 2, -2, -6, -10, -14, -17, @@ -56,6 +59,21 @@ static int rtw8821c_read_efuse(struct rtw_dev *rtwdev, u8 *log_map) efuse->rfe_option = map->rfe_option & 0x1f; efuse->rfe_option_full = map->rfe_option; + +#if IS_ENABLED(CONFIG_PCI) + if (rtw_hci_type(rtwdev) == RTW_HCI_TYPE_PCIE && dev_is_pci(rtwdev->dev)) { + struct pci_dev *pdev = to_pci_dev(rtwdev->dev); + + if (pdev->vendor == PCI_VENDOR_ID_REALTEK && + pdev->device == 0xc821 && + pdev->subsystem_vendor == 0x103c && + pdev->subsystem_device == 0x831a) { + efuse->rfe_option = 4; + efuse->rfe_option_full = 4; + rtw_info(rtwdev, "HP quirk auto-detected (10ec:c821 [103c:831a]): forced RFE option 4 (Aux antenna S1)\n"); + } + } +#endif efuse->rf_board_option = map->rf_board_option; efuse->crystal_cap = map->xtal_k; efuse->pa_type_2g = map->pa_type; -- 2.43.0