Multiple kernels and boot partitions selection

Multiple kernels and boot partitions selection

[gianluca]

Hello,
I was wondering if there is/are some standard way(s) to achieve a 
multiple boot selection on u-boot startup.

Let's say I have a bunch of partitions:

1- /dev/mmcblk0p7 with Debian 11 Bullseye

2- /dev/mmcblk0p5 with Debian 10 Buster

All of these partitions have the /boot/uImage kernel images, the 
/lib/modules/$(uname -r) drivers folders and /boot/dtb device-trees into 
their partition section.

u-boot has NOT the specific environment partition, i.e. it is located in 
the end of bootloader itself up to the maximum size of the bootloader 
partition. So, to be clear the /dev/mmcblk0p1 contains u-boot code & 
envar space.

If needed I can have a MB85RC64 a 24LC64 FRAM/EEPROM compatible memory 
chip to store information on boot.

Regards,
Gianluca
-- 
Eurek s.r.l.                          |
Electronic Engineering                | http://www.eurek.it
via Celletta 8/B, 40026 Imola, Italy  | Phone: +39-(0)542-609120
p.iva 00690621206 - c.f. 04020030377  | Fax:   +39-(0)542-609212

Re: Multiple kernels and boot partitions selection

[Quentin Schulz]

Hi Gianluca,

On 10/10/22 09:06, gianluca wrote:
> Hello,
> I was wondering if there is/are some standard way(s) to achieve a 
> multiple boot selection on u-boot startup.
> 
> Let's say I have a bunch of partitions:
> 
> 1- /dev/mmcblk0p7 with Debian 11 Bullseye
> 
> 2- /dev/mmcblk0p5 with Debian 10 Buster
> 
> All of these partitions have the /boot/uImage kernel images, the 
> /lib/modules/$(uname -r) drivers folders and /boot/dtb device-trees into 
> their partition section.
> 
> u-boot has NOT the specific environment partition, i.e. it is located in 
> the end of bootloader itself up to the maximum size of the bootloader 
> partition. So, to be clear the /dev/mmcblk0p1 contains u-boot code & 
> envar space.
> 
> If needed I can have a MB85RC64 a 24LC64 FRAM/EEPROM compatible memory 
> chip to store information on boot.
> 

You can modify the U-Boot environment from userspace with fw_setenv from 
libubootenv (formerly u-boot(-fw)-tools). You can store from there which 
partition to use for the next boot in an environment variable.

Cheers,
Quentin

Re: Multiple kernels and boot partitions selection

[gianluca]

On 10/10/22 10:06, Quentin Schulz wrote:
> Hi Gianluca,
> 
> On 10/10/22 09:06, gianluca wrote:
>> Hello,
>> I was wondering if there is/are some standard way(s) to achieve a 
>> multiple boot selection on u-boot startup.
>>
>> Let's say I have a bunch of partitions:
>>
>> 1- /dev/mmcblk0p7 with Debian 11 Bullseye
>>
>> 2- /dev/mmcblk0p5 with Debian 10 Buster
>>
>> All of these partitions have the /boot/uImage kernel images, the 
>> /lib/modules/$(uname -r) drivers folders and /boot/dtb device-trees 
>> into their partition section.
>>
>> u-boot has NOT the specific environment partition, i.e. it is located 
>> in the end of bootloader itself up to the maximum size of the 
>> bootloader partition. So, to be clear the /dev/mmcblk0p1 contains 
>> u-boot code & envar space.
>>
>> If needed I can have a MB85RC64 a 24LC64 FRAM/EEPROM compatible memory 
>> chip to store information on boot.
>>
> 
> You can modify the U-Boot environment from userspace with fw_setenv from 
> libubootenv (formerly u-boot(-fw)-tools). You can store from there which 
> partition to use for the next boot in an environment variable.
> 

As far as I know, I suppose I need an extra (let's say FAT) partition 
with the uboot.env transcoded file.
Then, with the u-boot(-fw)-tools I can access them from userspace to 
change some envar like:

from:

loadimage=mmc 0:5 ${loadaddr} ${bootfile}

to:

loadimage=mmc 0:7 ${loadaddr} ${bootfile}


> fw_setenv loadimage 'mmc 0:7 ${loadaddr} ${bootfile}'


Is it right?

Regards
-- 
Eurek s.r.l.                          |
Electronic Engineering                | http://www.eurek.it
via Celletta 8/B, 40026 Imola, Italy  | Phone: +39-(0)542-609120
p.iva 00690621206 - c.f. 04020030377  | Fax:   +39-(0)542-609212