[U-Boot-Users] Fallback kernel

[U-Boot-Users] Fallback kernel

[Marco Stornelli]

Hi,


I'm using two Linux kernel a fallback (safe) kernel and a kernel
downloaded in flash via ethernet. I'd like that u-boot starts the
downloaded kernel, if this kernel fails for more than N times uboot
starts the fallback. Is there already something like in uboot or how can
I do that?

Thanks in advance.

Marco

[U-Boot-Users] Fallback kernel

[Wolfgang Denk]

In message <474A7B02.9090008@coritel.it> you wrote:
> 
> I'm using two Linux kernel a fallback (safe) kernel and a kernel
> downloaded in flash via ethernet. I'd like that u-boot starts the
> downloaded kernel, if this kernel fails for more than N times uboot
> starts the fallback. Is there already something like in uboot or how can
> I do that?

U-Boot supports the "bootcount" variable to implement the Boot  Count
Limit  feature  (see  CGL  Requirements  Definition).  However,  this
requires  a  little  processor  specific  support  which  so  far  is
available only on few CPUs (but trivial to add where missing).

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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
If you can't beat it or corrupt it, you pretend it was your  idea  in
the first place.                 - Terry Pratchett, _Guards! Guards!_

[U-Boot-Users] Fallback kernel

[Marco Stornelli]

Wolfgang Denk wrote:
>>
>> I'm using two Linux kernel a fallback (safe) kernel and a kernel
>> downloaded in flash via ethernet. I'd like that u-boot starts the
>> downloaded kernel, if this kernel fails for more than N times uboot
>> starts the fallback. Is there already something like in uboot or how
 >> can I do that?

>U-Boot supports the "bootcount" variable to implement the Boot Count
>Limit feature (see CGL Requirements Definition). However, this
>requires a little processor specific support which so far is
>available only on few CPUs (but trivial to add where missing).

>Best regards,

>Wolfgang Denk

Why does it require a little processor specific support? In the
bootcount_load and bootcount_store, we could use an uboot environment
variable to store and load the value (if the env is in flash for
example), isn't it?

[U-Boot-Users] Fallback kernel

[Detlev Zundel]

Hi Marco,

> Why does it require a little processor specific support? In the
> bootcount_load and bootcount_store, we could use an uboot environment
> variable to store and load the value (if the env is in flash for
> example), isn't it?

Because we do not want to erase a flash sector for every boot
iteration.  

Ok, this could be implemented in a more clever way, but this effort is
better spent on other areas of U-Boot when most CPUs offer some kind
of a "breadcrumb" register surviving resets.

Cheers
  Detlev

-- 
He thinks he's really smooth, but he's only C^1.
--
DENX Software Engineering GmbH,      MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich,  Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-40 Fax: (+49)-8142-66989-80 Email: dzu at denx.de