Date: Sun, 10 Feb 2013 00:07:33 -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: <E691571B-EA19-4485-BB02-7486685B44C7@bsdimp.com> In-Reply-To: <58DCA6BE-8C06-4F69-81A2-A3582FBB5B12@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>
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On Feb 10, 2013, at 12:03 AM, Tim Kientzle wrote: > On Feb 9, 2013, at 10:20 PM, Brett Wynkoop wrote: >>=20 >> I was thinking that we should be able to generate a generic image = that >> will boot on both the Pi and the Bone. Maybe a config file that >> includes the needed drivers for both boards. >=20 > I've thought about this and believe it is pretty routine, > though I've not had time to actually try implementing it. >=20 > This specific combination is simplified by the fact > that the boot bits are so different, so you can just > put them all on the same SD card image. >=20 > There are a few pieces you'll need to work through: > 1. An MSDOS partition with all the boot bits from both systems > 2. A kernel with all of the drivers for both systems > 3. ubldr will need to identify the board somehow > 4. ubldr will need to obtain the correct FDT uboot is supposed to be providing the correct FDT. IF we aren't using = it, we're doing FDT wrong and need to fix that. > Except for #3, this should all be entirely routine. >=20 > For #4, the trick is to not compile any DTB into the > kernel. Instead, the DTB is given to the kernel by > the boot bits: >=20 > * For RPi, this already happens: the first-stage boot > loads a DTB, ubldr uses "fdt addr" to access that DTB > in a known location and then passes it to the kernel. Doesn't the RPi's boot loader give our /boot/loader enough info to get = this without the fdt addr command? > * For Beaglebone, you can use loader.rc commands to load > the proper DTB from the UFS partition. I'm using the following > on my BeagleBone right now: > /boot/beaglebone.dtb > /boot/loader.rc contains > load /boot/kernel/kernel > load -t dtb /boot/beaglebone.dtb > autoboot why isnt' the beagle board's boot loader passing it to /boot/loader? > This should be an afternoon's work for someone who already > has a good understanding of FreeBSD boot processes. The real solution here is to get the FDT plumbed through from the boards = primary boot strap code into our code. Linux requires that this be = passed in via like r2 for Linux to boot. We should make use of that too. Warner
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