Date: Wed, 29 Jun 2016 16:31:19 -0600 From: Ian Lepore <ian@freebsd.org> To: Ed Maste <emaste@freebsd.org>, Tim Kientzle <tim@kientzle.com> Cc: freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: Booting FreeBSD on BeagleBone Black from microSD by default Message-ID: <1467239479.72182.94.camel@freebsd.org> In-Reply-To: <CAPyFy2BZJbcOA4VT3A8531zKK58-_iAKSe7RpoxR%2BM3_NJUqDA@mail.gmail.com> References: <20160413095534.B48EA406057@ip-64-139-1-69.sjc.megapath.net> <1460560419.52955.23.camel@freebsd.org> <CAPyFy2AHdog0GzLBDQWeg%2B494yWo73gEJzFBPS_v=Nz3YparUA@mail.gmail.com> <87D8B295-950F-4B9D-AF58-0455FC212087@kientzle.com> <CAPyFy2BZJbcOA4VT3A8531zKK58-_iAKSe7RpoxR%2BM3_NJUqDA@mail.gmail.com>
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On Wed, 2016-06-29 at 16:18 -0400, Ed Maste wrote: > On 29 June 2016 at 00:14, Tim Kientzle <tim@kientzle.com> wrote: > > > > If I remember correctly, the uboot provided on the stock eMMC image > > was configured to see if the SD card had a Linux kernel and load > > the kernel from that if it was there. If the SD did not have a > > Linux kernel, it would fall back to eMMC. > > Yeah. After looking a little more I think the eMMC uboot will read > uEnv.txt from the SD card and so it should somehow be possible to > chain to a next stage that way, but it does not support UFS and does > not have a 'bootelf' command. > > It is possible to have the eMMC uboot load something from a FAT file > system on the SD card and execute it (with something like fatload mmc > 1 <addr> <file>; go <addr>) but I don't yet know enough about the > boot > path here to build a suitable 3rd stage uboot. > > 1. eMMC SPL > 2. eMMC u-boot, loads uEnv.txt from SD > 3. SD u-boot > 4. SD ubldr > 5. kernel > > > Of course, if you’re willing to hold the boot switch, you can boot > > from SD without changing the eMMC. > > Right. My goal here would be to be able to produce a SD card image > that works out of the box, without using the boot switch or modifying > the eMMC in any way. > > My interest in being able to boot that way comes from a BSDCan > talk[1] > by Edicarla Andrade and Vincius Zavam. They have FreeBSD on a BBB > controlling a hexapod robot, but they weren't allowed to modify the > BBB (provided by their lab) in any way. So they have to press the > boot > switch every time they power it up. It's a shame that they're doing > something interesting with FreeBSD, yet have this minor but annoying > boot issue. > > [1] https://www.bsdcan.org/2016/schedule/events/658.en.html > Building a removable jumper wire for connecting pin 43 on connector P8 to ground (pin 1) with a 1k resistor will have the effect of continuously holding down the sd-boot button without modifying anything permanantly on the board. People who build robots should be able to handle that. :) -- Ian
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