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    SubjectRe: [BUG] staging: r8822be: RTL8822be can't find any wireless AP
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    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@lwfinger.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

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