On Tue, Jun 17, 2014 at 06:42:52AM +0200, Wolfgang Denk wrote: > Dear Larry, > > In message <5070a944-cc27-4388-91e5-78b0792e5...@usgs.gov> you wrote: > > > > A recent situation has awakened me to a a behavior of U-Boot that maybe > > should be changed. > > U-Boot related questions should better be discussed on the U-Boot > (rather than the ELDK) mailing list. I'm adding the U-Boot list on > Cc. > > > I am experimenting with a BeagleBone Black (BBB) single-board > > computer. Occasionally when I perform a reboot, the BBB never > > finishes booting Linux. When I happen to have a console cable > > connected, I see the U-Boot prompt. This explains why the BBB has not > > booted Linux. But it is a mystery why U-Boot is waiting for a command > > when I did not request interrupting the autoboot sequence. > > > > I found many others reporting the same experience -- and no solution. > > Until I found Andrew Glen's 10/28/2013 post at > > https://groups.google.com/forum/#!topic/beagleboard/aXv6An1xfqI about > > U-Boot hangs likely due to noise on the UART0 port. The solution he > > applied was to rebuild U-Boot to require specific text -- "uboot" -- > > to interrupt the autoboot sequence. (BBB have no flash, so there is > > no opportunity to permanently alter any U-Boot environment variables, > > if this is settable.) > > You should be able to store the environment on SDCard. > > > It occurs to me that this might be a more common occurrence on any > > number of circuit boards. > > No, this is in no way a common issue. If you have any such line noise > on a serial port, you should start looking for hardware (design) > problems. This is _not_ normal. IF several boards of a specific > brand show such a problem, then I'm willing to bet that it's caused by > broken (or simply too cheap) hardware design. > > No industrial grade board I've ever seen has any such issues. > Hello, I agree line noise on a serial port is a hardware design problem. But I have seen such problems on servers in data centers, where there was a lot of electrical noise coupled into the serial port cable, acting as an antenna coupling that noise into the serial port terminal. This only happened on a small percentage of that hardware model's instances in that lab, but it was fully investigated and was easily repeatable on the defective hardware. We patched the software to close a related security issue and documented the potential hardware issue. It wasn't an issue we cared to engage the hardware vendor about.
enjoy, Karen -- Karen Shaeffer Be aware: If you see an obstacle in your path, Neuralscape Services that obstacle is your path. Zen proverb _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
