Date:   Sat, 24 Mar 2018 00:01:05 +0100
From:   Rafał Miłecki <zajec5@...il.com>
To:     Juri Lelli <juri.lelli@...il.com>
Cc:     b43-dev <b43-dev@...ts.infradead.org>,
        Network Development <netdev@...r.kernel.org>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [QUESTION] Mainline support for B43_PHY_AC wifi cards

On 23 March 2018 at 15:09, Juri Lelli <juri.lelli@...il.com> wrote:
> On 23/03/18 14:43, Rafał Miłecki wrote:
>> Hi,
>>
>> On 23 March 2018 at 10:47, Juri Lelli <juri.lelli@...il.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). :)

Please paste the remaining part if you still got it.


>> > 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?

Driver being closed source and company not willing to open source it
is usually a big problem getting it mainline...

-- 
Rafał

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