[Buildroot] Buildroot: enable lib/firmware/brcm for rpi0w

[Peter Seiderer <ps.report@gmx.net>]

Hello Andreas,

On Tue, 30 Mar 2021 08:20:08 +0000, Andreas Ziegler <br015@umbiko.net> wrote:

> Hello Peter,
>
> On 2021-03-29 18:49, Peter Seiderer wrote:
> > Hello Andreas,
> >
> > On Fri, 26 Mar 2021 12:47:21 +0000, Andreas Ziegler <br015@umbiko.net>
> > wrote:
> >
> >> Hello Peter,
> >>
> >> On 2021-03-25 21:20, Peter Seiderer wrote:
> >> >
> >> > Many thanks for doing the tests!
> >> >
> >>
> >> Not at all; after getting confused with different versions and
> >> repositories, I wanted to understand the reason behind this.
> >>
> >> Short summary of my findings; I may state the obvious here, but it was
> >> new for me and maybe it helps someone with the same hazy knowledge
> >> about
> >> hardware engineering as myself:
> >>
> >> Broadcom sold its RF division to Cypress in 2016. Cypress now supports
> >> the legacy wireless /bluetooth /radio hardware from Broadcom; that is
> >> the reason why BCM* and CYW* versions of firmware exist, and
> >> linux-firmware removed the original Broadcom supplied binaries.
> >>
> >> Cypress does not directly sell to end customers, but provides silicon
> >> to
> >> hardware partners (AzureWave, Murata, ...), which in turn sell RF
> >> solutions. Cypress distributes firmware for their silicon chips
> >> (probably to same hardware partners).
> >>
> >> End product is some type of SOC (subsystem on chip); the benefit is
> >> that
> >> tuning and regulatory issues have been taken care of. The SOC
> >> manufacturer is responsible for supplying bluetooth patch (HCD),
> >> regulatory data (CLM) and firmware configuration (TXT).
> >>
> >> That means the firmware binary (BIN) can be obtained from any source,
> >> the other items (HCD, CLM, TXT) need to be sourced from the
> >> implementer.
> >>
> >> >> The LibreELEC repository (rpi-wifi-firmware) seems to have adopted
> >> >> this
> >> >> version in commit 7dbd877545ae15069f2bd0e73893af942500e23d on Jan. 25.
> >> >
> >> > So a good reason to stay with LibreELEC (and fix the firmware package
> >> > to
> >> > provide raspberrypi,4-model-b.txt as a link or copy, do you know if
> >> > missing
> >> > it has some disadvantages or produces only the firmware load warning or
> >> > is
> >> > there a fallback to plain brcmfmac43455-sdio.txt?), keeping up with
> >> > RPi-Distro...
> >>
> >> Yes, also my opinion to stay with LibreELEC. The repository is small,
> >> is
> >> updated in a timely manner, and is (slightly) better documented than
> >> RPi-Distro.
> >>
> >> There is one thing (apart from providing the missing link) I would
> >> propose: merge rpi-bt-firmware and rpi-wifi-firmware into
> >> rpi-rf-firmware, combining the code from both .mk and Config.in files.
> >> Functionality would be identical, but one less firmware package. If
> >> anyone is interested, I could provide a patch.
> >
> > +1 from my side...
>
> I will propose something via the mailing list.
>
>
> >> In recent kernels, firmware load tries board-specific path first, then
> >> falls back to firmware derived path [1]. If I remember correctly, in
> >> kernels < 5.0 the firmware load failed.
> >>
> >> >> There seem to be some bigger changes in the pipeline: linux-firmware
> >> >> removed the Broadcom redistributed binaries in January [4] for the
> >> >> 20210208 release; instead Cypress firmware should be used. The
> >> >> upstream
> >> >> repository for this firmware seems to be murata-wireless /
> >> >> cyw-fmac-fw [5]
> >> >>
> >> >> I need to look into this in detail at some other time ...
> >> >
> >> > Seems kind of (another) firmware mess...., different versions at
> >> > different
> >> > repositories...., all with the same name (instead of clear version
> >> > string)...
> >>
> >> There are at least three different versions available in Buildroot:
> >>
> >> (available in Buildroot, repo 'master' version listed respectively)
> >>    libreELEC		build 2021-01-04	version 7.45.229
> >>    linux-firmware	build 2020-09-18	version 7.45.221
> >>    murata-wireless	build 2020-09-18	version 7.45.221
> >> (not in buildroot)
> >>    rpi-distro		build 2021-01-04	version 7.45.229
> >>
> >> > Regards,
> >> > Peter
> >>
> >> Kind regards,
> >> Andreas
> >
> > Thanks again for the detailed information (and testing)!
> >
> > Did just sent out an patch adding the convenience firmware
> > configuration
> > links for RPi3A+, RPi3B+ and RPi4B (see [2])...
>
> Tested and works for me. Hardware used was RPi4B. I replied to your
> patch, adding two lines for additional boards using BCM43430 Hardware.
> One is in the Linux Firmware Repository (3B), the other is the one
> reported by Laurentiu Christian (0W). I hope this approach is
> acceptable.

A little bit unusual (but not completely out of the way)..., but some
remarks inline to the patch...., all in all I think an additional
patch (based on my one) would be easier...

Regards,
Peter


>
> > Regards,
> > Peter
> >
> > [2]
> > https://patchwork.ozlabs.org/project/buildroot/patch/20210329184503.10514-1-ps.report at gmx.net/
> >
> >>
> >> [1]
> >> https://elixir.bootlin.com/linux/v5.10.21/source/drivers/net/wireless/broadcom/brcm80211/brcmfmac/firmware.c#L616
> >> _______________________________________________
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> >> buildroot at busybox.net
> >> http://lists.busybox.net/mailman/listinfo/buildroot
>
> Kind regards,
> Andreas