linux-kernel - Re: [BUG] staging: r8822be: RTL8822be can't find any wireless AP

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Date:   Thu, 5 Jul 2018 12:06:43 -0500
From:   Larry Finger <Larry.Finger@...inger.net>
To:     Pkshih <pkshih@...ltek.com>,
        "drake@...lessm.com" <drake@...lessm.com>
Cc:     Shaofu <shaofu@...ltek.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "dan.carpenter@...cle.com" <dan.carpenter@...cle.com>,
        "colin.king@...onical.com" <colin.king@...onical.com>,
        "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        Birming Chiu <birming@...ltek.com>,
        "kvalo@...eaurora.org" <kvalo@...eaurora.org>,
        "frank@...eralsoftwareinc.com" <frank@...eralsoftwareinc.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux@...lessm.com" <linux@...lessm.com>,
        Steven Ting <steventing@...ltek.com>,
        Tony Chuang <yhchuang@...ltek.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "sgruszka@...hat.com" <sgruszka@...hat.com>,
        "jian-hong@...lessm.com" <jian-hong@...lessm.com>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>
Subject: Re: [BUG] staging: r8822be: RTL8822be can't find any wireless AP

On 07/05/2018 02:36 AM, Pkshih wrote:
> On Wed, 2018-07-04 at 10:33 -0500, Daniel Drake wrote:
>> On Wed, Jul 4, 2018 at 10:13 AM, Larry Finger <Larry.Finger@...inger.net> wrote:
>>> We will have to agree to disagree.
>>>
>>> I have no idea what the vendors are doing that cause some motherboards to
>>> need a different aspm value. What I do know is that we have had to live with
>>> the idiocy of some vendors saving a few pennies by only including a single
>>> antenna, rather than two, and then making a problem by miscoding the EFUSE
>>> bit that indicates which connector is actually in use. As we have no means
>>> that I know about to detect which boxes have the problem, a module parameter
>>> was created, just as in this case.
>>>
>>> I agree that drivers should work "out of the box", but finite resources and
>>> lack of vendor cooperation make this a goal that may not be attainable.
>>
>> As you touched on, the ideal situation is that Realtek solve the
>> issue. Ping-Ke Shih is on CC and I am adding a few more contacts from
>> the commit log. The context is that the r8822 driver fails on several
>> platforms unless setting aspm=0 (the default is 1).
> 
> It's hard to have all laptop or motherboards and all rtl8822be modules in my side,
> so what I can do is to analyze the issue when user encountered.
> 
>>
>> https://gist.github.com/dsd/20c05f0c6d66ee2ef9bfbb17f93f18ba
>> https://bugzilla.kernel.org/show_bug.cgi?id=199651
>>
>>
>> If we don't get a timely fix from Realtek though, I think there is a
>> key difference between the antenna selection headache and this one. In
>> the antenna case, there isn't a good value that you can set that will
>> work on all systems. If you change the default behaviour you will
>> solve the issue for some users while simultanously introducing the
>> problem on other systems that were previously fine.
>>
>> However in this case, it's highly likely that setting aspm=0 (off) by
>> default would work for everyone. It has the disadvantage of using a
>> bit more power, but especially with the indications that this issue
>> affects a significant number of systems, I think that having the
>> driver working out of the box everywhere is more important. The module
>> parameter can be left in place so that unaffected users that want to
>> save power can set aspm=1.
>>
> 
> I think this issue may be due to L1 latency, so below patch would be
> helpful but not sure because I don't have the same laptop.
> Is there anyone can help to test?
> 
> 
> diff --git a/drivers/staging/rtlwifi/rtl8822be/hw.c b/drivers/staging/rtlwifi/rtl8822be/hw.c
> index 7947edb239a1..88ba5b2fea6a 100644
> --- a/drivers/staging/rtlwifi/rtl8822be/hw.c
> +++ b/drivers/staging/rtlwifi/rtl8822be/hw.c
> @@ -803,7 +803,7 @@ static void _rtl8822be_enable_aspm_back_door(struct ieee80211_hw *hw)
>   		return;
>   
>   	pci_read_config_byte(rtlpci->pdev, 0x70f, &tmp);
> -	pci_write_config_byte(rtlpci->pdev, 0x70f, tmp | BIT(7));
> +	pci_write_config_byte(rtlpci->pdev, 0x70f, tmp | ASPM_L1_LATENCY << 3);

This patch loses the BIT(7). Did you really mean to do that?

I now agree that this is a bug. A similar problem had been found in a few boxes 
with RTL8723BE or RTL8821AE cards, but that it might apply here completely 
slipped through the ever larger cracks in my mind.

Larry