Date: Sun, 10 Feb 2013 20:49:19 -0700 From: Warner Losh <imp@bsdimp.com> To: Tim Kientzle <tim@kientzle.com> Cc: freebsd-arm@freebsd.org, Brett Wynkoop <wynkoop@wynn.com> Subject: Re: building RaspPi Images Message-ID: <7F7AE905-7A08-48EE-8905-8D688266739A@bsdimp.com> In-Reply-To: <1339E085-2B31-485D-9EED-9D0AFB7664C5@kientzle.com> References: <5116CB50.9080303@ceetonetechnology.com> <7757848F-45C6-4DEF-A4A2-5F900EB10A06@kientzle.com> <20130210012052.4d7e1a46@ivory.local> <58DCA6BE-8C06-4F69-81A2-A3582FBB5B12@kientzle.com> <E691571B-EA19-4485-BB02-7486685B44C7@bsdimp.com> <EB4A0D67-9813-47DA-B3DB-F1309B2773F5@kientzle.com> <8087503F-BE98-45B9-888B-044D9DA58B80@bsdimp.com> <20130210212025.009ee482@bender> <ADEA1B10-6C17-43C8-B364-8819593D312E@bsdimp.com> <1339E085-2B31-485D-9EED-9D0AFB7664C5@kientzle.com>
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On Feb 10, 2013, at 5:39 PM, Tim Kientzle wrote: > On Feb 10, 2013, at 6:56 AM, Warner Losh wrote: >>=20 >> Right, we're doing it wrong. Or rather, we're using the standalone = interface when we should be using the linux interface. >=20 > So you think that ubldr should startup like a Linux kernel? > That's an interesting idea=85 Hmmmm=85.. If it isn't getting the FDT via the alternate interface, then yes. >> The stand alone interface should, in theory, provide us with the DTB, = but the code that is in ubldr doesn't seem to be reliably getitng this = image. >=20 > I don't think anyone has spent time on this. We've > just been focused on "making it work" and the compiled-in > DTB does work for any single board. Ah, that makes sense. I just know the theory, not the practice. I = haven't had time for armv6 stuff... >> uboot is supposed pass dtb to us. We're using the self-hosted = interface, rather than the linux interface, to boot. uboot is supposed = to have a jump table that we find and use to get the dtb from it, but = that code seems to not be working reliably. >=20 > The interface works (I've spent a fair few hours fixing it), > but I don't think anyone has tried getting the DTB from it. We should try... > Any ideas for addressing the load-address problem? > E.g., RPi has initial RAM mapped starting at address 0 > and BeagleBone starts with RAM mapped to 0x80000000. > Right now, that means we can't even share ubldr across > those two systems because it has to be linked differently. I'm unsure how Linux deals with it... I'm guessing that if we can turn = on the vm translation early enough, then this won't matter... >> uboot gives linux images the DTB w/o any problem today, but you have = to run mkimage to get the image file to load into uboot for that to = work. >=20 > Actually, the statement above isn't quite right for RPi. > Linux on RPi doesn't use U-Boot. Well, all Linux kernels require DTBs today, although some compile it = into the image... > So we're currently > using: >=20 > RPi boot loader =3D> U-Boot =3D> ubldr =3D> kernel. >=20 > The RPi boot loader does load the FDT and will pass > it to a Linux kernel, but I don't think U-Boot implements > that part of the linux kernel startup (which is why ubldr > on RPi looks at a particular address in RAM to get > the FDT from the RPi boot loader). Ah, it implements the standard interface. That should be an option, = since it is relatively easy to do. Maybe I should give in and get a RPi :) Warner
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