netdev - Re: RTL8723BE performance regression

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Date:   Tue, 3 Apr 2018 21:51:18 -0500
From:   Larry Finger <Larry.Finger@...inger.net>
To:     João Paulo Rechi Vita <jprvita@...il.com>
Cc:     Yan-Hsuan Chuang <yhchuang@...ltek.com>,
        Ping-Ke Shih <pkshih@...ltek.com>,
        Birming Chiu <birming@...ltek.com>,
        Shaofu <shaofu@...ltek.com>,
        Steven Ting <steventing@...ltek.com>,
        Chaoming Li <chaoming_li@...lsil.com.cn>,
        Kalle Valo <kvalo@...eaurora.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Drake <drake@...lessm.com>,
        João Paulo Rechi Vita <jprvita@...lessm.com>,
        linux@...lessm.com
Subject: Re: RTL8723BE performance regression

On 04/03/2018 09:37 PM, João Paulo Rechi Vita wrote:
> On Tue, Apr 3, 2018 at 7:28 PM, Larry Finger <Larry.Finger@...inger.net> wrote:
> 
> (...)
> 
>> As the antenna selection code changes affected your first bisection, do you
>> have one of those HP laptops with only one antenna and the incorrect coding
>> in the FUSE?
> 
> Yes, that is why I've been passing ant_sel=1 during my tests -- this
> was needed to achieve a good performance in the past, before this
> regression. I've also opened the laptop chassis and confirmed the
> antenna cable is plugged to the connector labeled with "1" on the
> card.
> 
>> If so, please make sure that you still have the same signal
>> strength for good and bad cases. I have tried to keep the driver and the
>> btcoex code in sync, but there may be some combinations of antenna
>> configuration and FUSE contents that cause the code to fail.
>>
> 
> What is the recommended way to monitor the signal strength?

The btcoex code is developed for multiple platforms by a different group than 
the Linux driver. I think they made a change that caused ant_sel to switch from 
1 to 2. At least numerous comments at github.com/lwfinger/rtlwifi_new claimed 
they needed to make that change.

Mhy recommended method is to verify the wifi device name with "iw dev". Then 
using that device

sudo iw dev <dev_name> scan | egrep "SSID|signal"

Larry