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From:   Jes Sorensen <jes.sorensen@gmail.com>
Subject: Re: [PATCH] rtl8xxxu: Fix wifi low signal strength issue of RTL8723BU
To:     Chris Chiu <chiu@endlessm.com>, kvalo@codeaurora.org,
        davem@davemloft.net
Cc:     linux-wireless@vger.kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux@endlessm.com
References: <20190627095247.8792-1-chiu@endlessm.com>
Message-ID: <31f59db2-0e04-447b-48f8-66ea53ebfa7d@gmail.com>
Date:   Tue, 2 Jul 2019 08:44:36 -0400
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On 6/27/19 5:52 AM, Chris Chiu wrote:
> 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@endlessm.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;

This part I would like to ask you take a good look at the other chips to
make sure you don't break support for 8192cu, 8723au, 8188eu with this.

Cheers,
Jes