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Date:   Fri, 23 Mar 2018 15:09:19 +0100
From:   Juri Lelli <juri.lelli@gmail.com>
To:     =?utf-8?B?UmFmYcWCIE1pxYJlY2tp?= <zajec5@gmail.com>
Cc:     b43-dev <b43-dev@lists.infradead.org>,
        Network Development <netdev@vger.kernel.org>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [QUESTION] Mainline support for B43_PHY_AC wifi cards
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Hi,

thanks a lot for your reply!

On 23/03/18 14:43, Rafał Miłecki wrote:
> Hi,
> 
> On 23 March 2018 at 10:47, Juri Lelli <juri.lelli@gmail.com> wrote:
> > I've got a Dell XPS 13 9343/0TM99H (BIOS A15 01/23/2018) mounting a
> > BCM4352 802.11ac (rev 03) wireless card and so far I've been using it on
> > Fedora with broadcom-wl package (which I believe installs Broadcom's STA
> > driver?). It works good apart from occasional hiccups after suspend.
> >
> > I'd like to get rid of that dependency (you can understand that it's
> > particularly annoying when testing mainline kernels), but I found out
> > that support for my card is BROKEN in mainline [1]. Just to see what
> > happens, I forcibly enabled it witnessing that it indeed crashes like
> > below as Kconfig warns. :)
> >
> >  bcma: bus0: Found chip with id 0x4352, rev 0x03 and package 0x00
> >  bcma: bus0: Core 0 found: ChipCommon (manuf 0x4BF, id 0x800, rev 0x2B, class 0x0)
> >  bcma: bus0: Core 1 found: IEEE 802.11 (manuf 0x4BF, id 0x812, rev 0x2A, class 0x0)
> >  bcma: bus0: Core 2 found: ARM CR4 (manuf 0x4BF, id 0x83E, rev 0x02, class 0x0)
> >  bcma: bus0: Core 3 found: PCIe Gen2 (manuf 0x4BF, id 0x83C, rev 0x01, class 0x0)
> >  bcma: bus0: Core 4 found: USB 2.0 Device (manuf 0x4BF, id 0x81A, rev 0x11, class 0x0)
> >  bcma: Unsupported SPROM revision: 11
> >  bcma: bus0: Invalid SPROM read from the PCIe card, trying to use fallback SPROM
> >  bcma: bus0: Using fallback SPROM failed (err -2)
> >  bcma: bus0: No SPROM available
> >  bcma: bus0: Bus registered
> >  b43-phy0: Broadcom 4352 WLAN found (core revision 42)
> >  b43-phy0: Found PHY: Analog 12, Type 11 (AC), Revision 1
> >  b43-phy0: Found Radio: Manuf 0x17F, ID 0x2069, Revision 4, Version 0
> >  BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> 
> This isn't really useful without a full backtrace.

Sure. I cut it here because I didn't expect people to debug what is
already known to be broken (but still it seemed to carry useful
information about the hw). :)

> > So, question: is replacing my card the only way I can get rid of this
> > downstream dependency? :(
> 
> It's definitely the cheapest way. Getting AC PHY into anything usable
> (proper setup that will allow Tx & Rx anything) would probably take
> weeks or months of development. I'm not even going to estimate cost of
> adding support for 802.11n and 802.11ac features. I was the last
> person actively working on b43, right now I spend my free time on
> other hobby projects. Few people were planning to help but it seems it
> never worked out for them.

I see. Just wondering why even if Broadcom's STA solution seems to work
fine, it is not mainline. Maybe a maintenance problem? But Fedora ships
with very recent kernels, so I'd expect the driver to work with mainline
(I tried compiling that against mainline, but I got errors that I didn't
spend time figuring out how to fix).

Do you know what's the deal w.r.t. the STA driver?

Best,

- Juri