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* [PATCH] wifi: rtw88: 8821c: Add HP single-antenna quirk
       [not found] <20260911100904.50320-1-eexto.ref@aol.com>
@ 2026-09-11 10:09 ` not-eexto
  2026-09-13  2:15   ` Ping-Ke Shih
  0 siblings, 1 reply; 3+ messages in thread
From: not-eexto @ 2026-09-11 10:09 UTC (permalink / raw)
  To: pkshih; +Cc: linux-wireless, not-eexto

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 <eexto@aol.com>
---
 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 <linux/pci.h>
+#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


^ permalink raw reply related	[flat|nested] 3+ messages in thread

* [PATCH] wifi: rtw88: 8821c: Add HP single-antenna quirk
@ 2026-09-11 10:56 not-eexto
  0 siblings, 0 replies; 3+ messages in thread
From: not-eexto @ 2026-09-11 10:56 UTC (permalink / raw)
  To: pkshih; +Cc: linux-wireless, not-eexto

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 <p17232763@gmail.com>
---
 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 <linux/pci.h>
+#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


^ permalink raw reply related	[flat|nested] 3+ messages in thread

* RE: [PATCH] wifi: rtw88: 8821c: Add HP single-antenna quirk
  2026-09-11 10:09 ` [PATCH] wifi: rtw88: 8821c: Add HP single-antenna quirk not-eexto
@ 2026-09-13  2:15   ` Ping-Ke Shih
  0 siblings, 0 replies; 3+ messages in thread
From: Ping-Ke Shih @ 2026-09-13  2:15 UTC (permalink / raw)
  To: not-eexto; +Cc: linux-wireless@vger.kernel.org

not-eexto <eexto@aol.com> wrote:
> 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 <eexto@aol.com>

Should use your full real name.

You sent the same patch by different mail address. I'll drop previous one.

> ---
>  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 <linux/pci.h>
> +#endif

If this is the only one platform which needs this kind of quirk. Add an entry
to rtw_pci_quirks[].

> 
>  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;

I don't see rtw88 has ' rfe_option_full' ?

> +                       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


^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2026-09-13  2:15 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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     [not found] <20260911100904.50320-1-eexto.ref@aol.com>
2026-09-11 10:09 ` [PATCH] wifi: rtw88: 8821c: Add HP single-antenna quirk not-eexto
2026-09-13  2:15   ` Ping-Ke Shih
2026-09-11 10:56 not-eexto

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