Re: eMMC support

[Joel Stanley]

On Wed, 10 Feb 2021 at 09:56, Cédric Le Goater <clg@kaod.org> wrote:
>
> Hello Sai Pavan,
>
> [ ... ]
>
> >>> The patchset is in the aspeed-6.0 branch :
> >>>
> >>>     df91d012672c Cédric Le Goater - hw/arm/aspeed: Load eMMC first boot
> >>>                                     area as a boot rom
> >>>     27b75a7ad322 Cédric Le Goater - hw/arm/aspeed: Add eMMC property
> >>>     2836cf5a15a1 Joel Stanley - hw/arm/aspeed: Set boot device to emmc
> >
> > [Sai Pavan Boddu] I see you guys have implemented the boot area access here,
>
> The boot partition modeling fits our needs to boot the Aspeed machine
> but this is very custom.
>
> > I was assuming, your use-case just need to access data from boot partitions.
> > We are not implementing eMMC boot operations or Alternative bootmode right ?
>
> Joel could say more about it ?

The solution I came up with has room for improvement. There's no way
to tell the qemu sd device what boot partitions it should expect to
find, and likewise there's no way for the emulated machine to check
that the image is formatted in the way it expects.

If there was a way to add metadata to the image (through qcow2?) then
we could use this to define the boot partition sizes in the image, and
have the model use these numbers to populate CSD_EXT. It's only an
idea, and I don't know if qcow2 supports this kind of metadata.

Cheers,

Joel