On Thu, Apr 23, 2015 at 05:10:21PM +1000, Craig McQueen wrote: > I'm building Yocto for BeagleBone using the meta-ti layer and the kernel and > U-Boot provided by that layer. > > I'm having some trouble understanding the location where U-Boot saves its > environment for BeagleBone Black. > > After doing some reading, it looks as though it might be saving environment > on a "special" eMMC boot partition (which is not the same as the FAT16 > partition 1 I created to store MLO and u-boot.img). > > However, this is only when booting from the on-board eMMC I think. When > booting from SD card, where is environment stored? I can do "saveenv" command > in U-Boot, and it says it's saving it to MMC. > > U-Boot# saveenv > Saving Environment to MMC... > Writing to MMC(1)... done > > But then after a reboot, it says: > > MMC: block number 0x100 exceeds max(0x0) > MMC: block number 0x200 exceeds max(0x0) > *** Error - No Valid Environment Area found > Using default environment > > So does that mean that U-Boot can't use a saved environment when booting from > SD card? > > Actually, based on some simple testing, it seems that it _is_ writing to the > boot partition of the on-board eMMC, and loading it when it reboots from SD > card, despite the error message. This is confusing.
First, please post the whole boot log, not just part. That will make it easier to explain what is going on I believe. > What about the case of a board with no eMMC, such as BeagleBone White? Where > would it save environment then? There's a number of different places that env could be stored. I forget if meta-ti is patching things such that it saves to a file on the FAT partition for example. > How can I erase the saved environment when booting from eMMC, to ensure that > U-Boot defaults will be used? I see that when Linux boots, there are block > devices /dev/mmcblk0boot0 and /dev/mmcblk0boot1. But it seems I can't write > to them: > > # dd if=/dev/zero of=/dev/mmcblk0boot1 bs=1k count=1k > dd: writing '/dev/mmcblk0boot1': Operation not permitted > 1+0 records in > 0+0 records out In Linux you need to unlock these first. Google should point out the file you need to write to. -- Tom -- _______________________________________________ yocto mailing list yocto@yoctoproject.org https://lists.yoctoproject.org/listinfo/yocto
