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

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Date:   Fri, 6 Jul 2018 03:34:30 +0000
From:   Pkshih <pkshih@...ltek.com>
To:     "Larry.Finger@...inger.net" <Larry.Finger@...inger.net>,
        "drake@...lessm.com" <drake@...lessm.com>
CC:     "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "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>,
        Shaofu <shaofu@...ltek.com>,
        "jian-hong@...lessm.com" <jian-hong@...lessm.com>
Subject: Re: [BUG] staging: r8822be: RTL8822be can't find any wireless AP

On Thu, 2018-07-05 at 12:06 -0500, Larry Finger wrote:
> 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.
> 

Yes, I remove BIT(7) intentionally, because this is defined as reserved bit in rtl8822be.
For the older chips, I need to check with my colleagues.

Regards,
PK