RE: eMMC support

[Sai Pavan Boddu]

Hi Joel

> -----Original Message-----
> From: Joel Stanley <joel@jms.id.au>
> Sent: Wednesday, February 10, 2021 6:35 PM
> To: Cédric Le Goater <clg@kaod.org>
> Cc: Sai Pavan Boddu <saipava@xilinx.com>; Edgar Iglesias <edgari@xilinx.com>;
> Andrew Jeffery <andrew@aj.id.au>; qemu-devel@nongnu.org; Philippe
> Mathieu-Daudé <f4bug@amsat.org>
> Subject: Re: eMMC support
> 
> 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.
[Sai Pavan Boddu] I guess bits of PARTITION_CONFIG[PARTITION_ACCESS], would 
tell SD which boot partition needs to be enabled.
> 
> 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.
[Sai Pavan Boddu] yeah nice. I don’t know if qemu-img has any option as such.
Anyway only few fields in CSD_EXT are useful for us, which should be ok to 
implement as properties.

Regards,
Sai Pavan
> 
> Cheers,
> 
> Joel