[U-Boot] u-boot retries with fallback to other images
Hi,
Is there any documentation or u-boot support for having a list of boot images to try, starting with the first in the list, trying 1, 2 or 3 times, then trying the next in the list.
e.g. boot kernel at mmcblk0p3, then mmcblk0p2, then mmcblk1p2, then tftp/nfs last resort fallback ? or boot off partition 3 of eMMC, then partition2 of eMMC, then partition 2 of SD card, then tftp/nfs ?
I've seen some info on google that says this is possible. I'm just looking for good documentation that can explain how to set it all up.
Thanks, Brendan.
Dear Brendan,
In message 5663B74E.7000204@etrix.com.au you wrote:
Is there any documentation or u-boot support for having a list of boot images to try, starting with the first in the list, trying 1, 2 or 3 times, then trying the next in the list.
e.g. boot kernel at mmcblk0p3, then mmcblk0p2, then mmcblk1p2, then tftp/nfs last resort fallback ? or boot off partition 3 of eMMC, then partition2 of eMMC, then partition 2 of SD card, then tftp/nfs ?
Define a set of boot commands, say bootcmd1, bootcmd2, ... and then simply do
run bootcmd1; run bootcmd2; ...
The furst one that succeeds will not return.
Note that the key problem with such a simplistic approach is that it will not help you in case an image looks OK, but hangs during boot - in that case, you need a watchdow and support for the bootcount feature.
Best regards,
Wolfgang Denk
Hi Wolfgang,
On 7/12/2015 5:23 PM, Wolfgang Denk wrote:
Dear Brendan,
In message 5663B74E.7000204@etrix.com.au you wrote:
Is there any documentation or u-boot support for having a list of boot images to try, starting with the first in the list, trying 1, 2 or 3 times, then trying the next in the list.
e.g. boot kernel at mmcblk0p3, then mmcblk0p2, then mmcblk1p2, then tftp/nfs last resort fallback ? or boot off partition 3 of eMMC, then partition2 of eMMC, then partition 2 of SD card, then tftp/nfs ?
Define a set of boot commands, say bootcmd1, bootcmd2, ... and then simply do
run bootcmd1; run bootcmd2; ...
The furst one that succeeds will not return.
Note that the key problem with such a simplistic approach is that it will not help you in case an image looks OK, but hangs during boot - in that case, you need a watchdow and support for the bootcount feature.
Best regards, Wolfgang Denk
Yes, the watchdog and bootcount feature is the advanced stuff I'm looking for. I would think this has been implemented numerous times, and I didn't want to reinvent the wheel if there was some commonly used infrastructure to support this. If software does boot, then at some stage would set a u-boot variable to say everything booted ok, so that it can be used again on next boot.
My use case is not that uncommon -- lots of embedded devices installed in remote locations that are not easily accessible, but require remote monitor and software updates.
Is there anything that is "standard" in u-boot to support this? Or any work that is published that has attempted this?
Thanks, Brendan.
Dear Brendan,
In message 5665634E.8050004@etrix.com.au you wrote:
Note that the key problem with such a simplistic approach is that it will not help you in case an image looks OK, but hangs during boot - in that case, you need a watchdow and support for the bootcount feature.
...
Yes, the watchdog and bootcount feature is the advanced stuff I'm looking for. I would think this has been implemented numerous times, and I didn't want to reinvent the wheel if there was some commonly used infrastructure to support this.
Indeed both watchdog support and bootcounter are standard features that are in active use by a number of boards.
My use case is not that uncommon -- lots of embedded devices installed in remote locations that are not easily accessible, but require remote monitor and software updates.
Indeed - a pretty common requirement.
Is there anything that is "standard" in u-boot to support this? Or any work that is published that has attempted this?
It's all in mainline...
Best regards,
Wolfgang Denk
participants (2)
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Brendan Simon (eTRIX) -
Wolfgang Denk