Date: Wed, 11 Jul 2012 20:29:06 -0600 From: Warner Losh <imp@bsdimp.com> To: Tim Kientzle <kientzle@freebsd.org> Cc: freebsd-arm@freebsd.org, David Chisnall <theraven@freebsd.org> Subject: Re: ARM at the Cambridge DevSummit Message-ID: <9532201C-0E39-4E2E-A2D8-CBCF4FB219DC@bsdimp.com> In-Reply-To: <2FFA7683-9919-4BB9-9B65-F49494572FB2@freebsd.org> References: <422C3A88-2AC6-484E-A34D-CC61EB761DC2@FreeBSD.org> <2FFA7683-9919-4BB9-9B65-F49494572FB2@freebsd.org>
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On Jul 11, 2012, at 8:13 PM, Tim Kientzle wrote: >=20 > On Jul 11, 2012, at 6:10 AM, David Chisnall wrote: >=20 >> Hello all of the FreeBSD/ARM flavoured people, >>=20 >> The Cambridge DevSummit in August will be attended by some people = from ARM, so it would be good to have as many FreeBSD/ARM developers = there as possible. If you haven't signed up yet, please do. >>=20 >> Please also let me have a list of topics that you'd like to discuss = with people from ARM so that I can try to make sure that relevant people = attend. >=20 > I won't be able to attend, but after some recent work on > ARM booting, I'm very curious if there are emerging > conventions (I hesitate to use the word "standards") > for how ARM systems boot. There's two standards that we can/should follow. First, there's uldr, = which is the uboot + /boot/loader path. This works well enough, but has = a weak point here and there. The FDT stuff is the future for most ARM = platforms, but currently is limited to the Marvel SoCs (where it is = pretty much mandatory). I believe we should adapt this for the new = armv6 families that are coming in, since new Linux platforms have to = support it, and these are "new" by that definition. The second is a more direct interface to uboot. Or rather a more direct = interface to the Linux standard booting protocol. I've made some = sketches on the wall, and filled in a few things here. However, it is = very incomplete. I've been unable to test it because I've been unable = to build a bootm compatible image yet, and uboot only uses the Linux ABI = when you boot with bootm. For the 'go' interface that's documented on = the FreeBSDAtmel wiki page, args are passed in another way. I can boot = with that, but not bootm. To be honest, I've not tracked the problem = much yet, other than to notice it... > Warner's been talking about working towards a true > GENERIC kernel on ARM. That looks almost feasible, > but we still seem a long ways from being able to build > a generic bootloader. Yes. There's the whole point of the boot args stuff I've done: to try = to have a standardish interface to the kernel. All the boot loader = interfaces would parse the goo from the boot loader and set = variables/structures in the kernel that the rest of the kernel = interfaces to. > Is this likely to change? I'd like it to, but it is a lot of work, and there's a lot of = rototilling to do in the Atmel area... Warner=
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