Re: [Buildroot] [PATCH v3 4/4] configs/rock5b: enable uboot-env on the SD card

[Niklas Cassel via buildroot <buildroot@buildroot.org>]

Hello Thomas,

On Tue, Oct 22, 2024 at 10:50:40PM +0200, Thomas Petazzoni wrote:
> Hello Niklas,
> 
> On Wed, 16 Oct 2024 15:24:43 +0200
> Niklas Cassel via buildroot <buildroot@buildroot.org> wrote:
> 
> > +	partition uboot-env {
> > +		offset = 16M
> > +		size = 64K
> > +	}
> > +
> >  	partition rootfs {
> >  		partition-type-uuid = root-arm64
> >  		image = "rootfs.ext2"
> > +		bootable = true
> >  	}
> >  }
> > diff --git a/board/radxa/rock5b/u-boot.fragment b/board/radxa/rock5b/u-boot.fragment
> > new file mode 100644
> > index 0000000000..e332bc0c79
> > --- /dev/null
> > +++ b/board/radxa/rock5b/u-boot.fragment
> > @@ -0,0 +1,5 @@
> > +CONFIG_SYS_MMC_ENV_DEV=1
> > +CONFIG_ENV_SIZE=0x10000
> > +CONFIG_ENV_OFFSET=0x1000000
> 
> Hardcoding an offset isn't super nice. Could you try using
> CONFIG_SYS_MMC_ENV_PART instead? It isn't clear to me how it interacts
> CONFIG_ENV_OFFSET.

I can't use CONFIG_SYS_MMC_ENV_PART.

If you read the Kconfig help text:
"""
MMC hardware partition device number on the platform where the
environment is stored.  Note that this is not related to any software
defined partition table but instead if we are in the user area, which is
partition 0 or the first boot partition, which is 1 or some other defined
partition.
"""

So CONFIG_SYS_MMC_ENV_PART is about specifying a MMC specific hwpartition,
which is different from a GPT partition (which is usually stored in a MMC
"user area" hwpartition).

I sent a v4 of this patch that uses the uboot feature which automatically
loads the u-boot environment from a GPT partition which has the
"u-boot-env" GPT partition type GUID instead:
https://lore.kernel.org/buildroot/20241023182509.2808544-1-niklas.cassel@wdc.com/


Kind regards,
Niklas
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