linux-kernel - [PATCH] rtl8xxxu: Fix wifi low signal strength issue of RTL8723BU

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Message-Id: <20190627095247.8792-1-chiu@endlessm.com>
Date:   Thu, 27 Jun 2019 17:52:47 +0800
From:   Chris Chiu <chiu@...lessm.com>
To:     jes.sorensen@...il.com, kvalo@...eaurora.org, davem@...emloft.net
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux@...lessm.com
Subject: [PATCH] rtl8xxxu: Fix wifi low signal strength issue of RTL8723BU

The WiFi tx power of RTL8723BU is extremely low after booting. So
the WiFi scan gives very limited AP list and it always fails to
connect to the selected AP. This module only supports 1x1 antenna
and the antenna is switched to bluetooth due to some incorrect
register settings.

This commit hand over the antenna control to PTA, the wifi signal
will be back to normal and the bluetooth scan can also work at the
same time. However, the btcoexist still needs to be handled under
different circumstances. If there's a BT connection established,
the wifi still fails to connect until disconneting the BT.

Signed-off-by: Chris Chiu <chiu@...lessm.com>
---
 drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_8723b.c | 9 ++++++---
 drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c  | 3 ++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_8723b.c b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_8723b.c
index 3adb1d3d47ac..6c3c70d93ac1 100644
--- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_8723b.c
+++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_8723b.c
@@ -1525,7 +1525,7 @@ static void rtl8723b_enable_rf(struct rtl8xxxu_priv *priv)
 	/*
 	 * WLAN action by PTA
 	 */
-	rtl8xxxu_write8(priv, REG_WLAN_ACT_CONTROL_8723B, 0x04);
+	rtl8xxxu_write8(priv, REG_WLAN_ACT_CONTROL_8723B, 0x0c);
 
 	/*
 	 * BT select S0/S1 controlled by WiFi
@@ -1568,9 +1568,12 @@ static void rtl8723b_enable_rf(struct rtl8xxxu_priv *priv)
 	rtl8xxxu_gen2_h2c_cmd(priv, &h2c, sizeof(h2c.ant_sel_rsv));
 
 	/*
-	 * 0x280, 0x00, 0x200, 0x80 - not clear
+	 * Different settings per different antenna position.
+	 * Antenna switch to BT: 0x280, 0x00 (inverse)
+	 * Antenna switch to WiFi: 0x0, 0x280 (inverse)
+	 * Antenna controlled by PTA: 0x200, 0x80 (inverse)
 	 */
-	rtl8xxxu_write32(priv, REG_S0S1_PATH_SWITCH, 0x00);
+	rtl8xxxu_write32(priv, REG_S0S1_PATH_SWITCH, 0x80);
 
 	/*
 	 * Software control, antenna at WiFi side
diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
index 8136e268b4e6..87b2179a769e 100644
--- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
+++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
@@ -3891,12 +3891,13 @@ static int rtl8xxxu_init_device(struct ieee80211_hw *hw)
 
 	/* Check if MAC is already powered on */
 	val8 = rtl8xxxu_read8(priv, REG_CR);
+	val16 = rtl8xxxu_read16(priv, REG_SYS_CLKR);
 
 	/*
 	 * Fix 92DU-VC S3 hang with the reason is that secondary mac is not
 	 * initialized. First MAC returns 0xea, second MAC returns 0x00
 	 */
-	if (val8 == 0xea)
+	if (val8 == 0xea || !(val16 & BIT(11)))
 		macpower = false;
 	else
 		macpower = true;
-- 
2.11.0