{"id":763,"date":"2010-10-19T19:47:17","date_gmt":"2010-10-20T02:47:17","guid":{"rendered":"http:\/\/www.graphics-muse.org\/wp\/?p=763"},"modified":"2010-10-21T14:01:28","modified_gmt":"2010-10-21T21:01:28","slug":"beaglebox-which-u-boot-am-i-fiddling-with","status":"publish","type":"post","link":"https:\/\/www.graphics-muse.org\/wp\/?p=763","title":{"rendered":"BeagleBox: which u-boot am I fiddling with?"},"content":{"rendered":"

I fiddled with the u-boot env variables tonight to try and resolve the S-Video problem.\u00a0 One trick from the BeagleBoard mailing list said to set omapfb.mode=tv:ntsc<\/em><\/span> and omapdss.def_disp=tv<\/em><\/span>.\u00a0 I tried this but found that if I tried to run the boot manually\u00a0 to pick up these changes to the bootargs the boot failed for various reasons related to how the rest of the environment is set up.\u00a0 The only boot that works (albeit without S-Video support properly configured) is the default boot.\u00a0 This boot reads the boot.scr<\/strong><\/span> file from the SD card, which is a text file from the Angstrom distro that has been run through with the mkimage<\/em> tool from u-boot.\u00a0 Browsing recipes\/angstrom\/angstrom-uboot-scripts<\/span> I find a couple of possible scripts that may be the one being used for boot.scr.\u00a0 I’ll either have to decipher the angstrom build process for BeagleBoard or just ask on the mailing list for which one is the one used to create the validation images for the C4 boards.<\/p>\n

This idea of setting up u-boot via files on the SD card is interesting.\u00a0 I can see why they’d want to do it – it’s easier to reconfigure u-boot by updating a file on the SD card than trying to rebuild u-boot and\/or flashing a ROM.\u00a0 What I don’t think I like (at least not yet, I may change my mind) is how this differs from the way u-boot is used in general.\u00a0 Maybe this has always been done and I’ve just never seen it.\u00a0 But its another step in my build process that I’ll need to add if I want to keep using the current x-loader on the C4 board I have.<\/p>\n

Of course, if I change the boot loader (u-boot) on the SD card to something other than what the BeagleBoard validation images use it’s questionable if the use of the boot scripts will still work.\u00a0 I’m not sure if the x-loader is loading u-boot from the SD card initially and *that* is the one that calls the boot.scr or if there is a u-boot in the ROM that loads first and *that* is the one whose env vars I’ve been mucking with.<\/p>\n

I think I need to ask the list for help on this.\u00a0 If anyone reads this and has the answer, please post a comment.\u00a0 Thanks!<\/p>\n

Update: 2010-10-20<\/strong><\/span><\/p>\n

D’oh!\u00a0 Stupidity is setting in.\u00a0 It’s obvious there are two u-boots.\u00a0 The first one provided me the command line interface.\u00a0 I know this because I actually loaded the second one from the SD card!<\/p>\n