[U-Boot] u-boot retries with fallback to other images

[U-Boot] u-boot retries with fallback to other images

[Brendan Simon]

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.

[U-Boot] u-boot retries with fallback to other images

[Wolfgang Denk]

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

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"It is better to have tried and failed than to have  failed  to  try,
but the result's the same."                           - Mike Dennison

[U-Boot] u-boot retries with fallback to other images

[Brendan Simon]

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.

[U-Boot] u-boot retries with fallback to other images

[Wolfgang Denk]

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

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Committee, n.:  A group of men who individually can do nothing but as
a group decide that nothing can be done.                 - Fred Allen