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From:   Daniel Drake <drake@endlessm.com>
Date:   Fri, 12 Jul 2019 15:25:52 +0800
Message-ID: <CAD8Lp45Qe-GKrtCR=d4GCx+PPAtmMQfHK2VpmA_yHMNFJ3ijww@mail.gmail.com>
Subject: Re: [PATCH v2] rtl8xxxu: Fix wifi low signal strength issue of RTL8723BU
To:     Chris Chiu <chiu@endlessm.com>
Cc:     Jes Sorensen <jes.sorensen@gmail.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        David Miller <davem@davemloft.net>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Linux Upstreaming Team <linux@endlessm.com>
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On Fri, Jul 5, 2019 at 10:27 AM Chris Chiu <chiu@endlessm.com> wrote:
> Per the code before REG_S0S1_PATH_SWITCH setting, the driver has told
> the co-processor the antenna is inverse.
>         memset(&h2c, 0, sizeof(struct h2c_cmd));
>         h2c.ant_sel_rsv.cmd = H2C_8723B_ANT_SEL_RSV;
>         h2c.ant_sel_rsv.ant_inverse = 1;
>         h2c.ant_sel_rsv.int_switch_type = 0;
>         rtl8xxxu_gen2_h2c_cmd(priv, &h2c, sizeof(h2c.ant_sel_rsv));
>
> At least the current modification is consistent with the antenna
> inverse setting.
> I'll verify on vendor driver about when/how the inverse be determined.

I checked this out. The codepath hit hardcodes it to the AUX port,
i.e. "inverted" setup:

EXhalbtc8723b1ant_PowerOnSetting():
    if(pBtCoexist->chipInterface == BTC_INTF_USB)
    {
        // fixed at S0 for USB interface
        pBtCoexist->fBtcWrite4Byte(pBtCoexist, 0x948, 0x0);

        u1Tmp |= 0x1;    // antenna inverse
        pBtCoexist->fBtcWriteLocalReg1Byte(pBtCoexist, 0xfe08, u1Tmp);

        pBoardInfo->btdmAntPos = BTC_ANTENNA_AT_AUX_PORT;
  }

So I'm further convinced that these performance-enhancing changes are
increasing consistency with the vendor driver.

Daniel