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

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Message-ID: <CAB4CAwcEdcg91Bgb+JoCdk_zQKsWT-K+cb07-5mrrx+__X2RMA@mail.gmail.com>
Date:   Wed, 3 Jul 2019 11:25:11 +0800
From:   Chris Chiu <chiu@...lessm.com>
To:     Jes Sorensen <jes.sorensen@...il.com>
Cc:     Kalle Valo <kvalo@...eaurora.org>,
        David Miller <davem@...emloft.net>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        Linux Upstreaming Team <linux@...lessm.com>
Subject: Re: [PATCH] rtl8xxxu: Fix wifi low signal strength issue of RTL8723BU

On Tue, Jul 2, 2019 at 8:44 PM Jes Sorensen <jes.sorensen@...il.com> wrote:
>
> 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@...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;
>
> 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

I checked the vendor code of 8192cu and 8188eu, they don't have this part
of code to check the REG_CR before power on sequence. I can only find
similar code in rtl8723be.
if (tmp_u1b != 0 && tmp_u1b !=0xea)
    rtlhal->mac_func_enable = true;

By definition, the BIT(11) of REG_SYS_CLKR in rtl8xxxu_regs.h is
SYS_CLK_MAC_CLK_ENABLE. It seems to make sense to check this value
for macpower no matter what chip it is. I think I can make it more
self-expressive
as down below.

 if (val8 == 0xea || !(val16 & SYS_CLK_MAC_CLK_ENABLE))

And per the comment, this code is for 92DU-VC S3 hang problem and I think an
OR check for SYS_CLK_MAC_CLK_ENABLE is still safe for this.

Chris