[U-Boot] IMX6 DM_USB / DM_MMC requires OF_CONTROL?

[Tim Harvey]

On Tue, Feb 19, 2019 at 10:38 AM Fabio Estevam <festevam at gmail.com> wrote:
>
> Hi Tim,
>
> On Tue, Feb 19, 2019 at 3:24 PM Tim Harvey <tharvey at gateworks.com> wrote:
> >
> > Greetings,
> >
> > I'm seeing that I need to switch my IMX6 board support
> > (board/gateworks/gw_ventana) over to DM_USB and DM_MMC right away
> > (v2019.04) and I notice enabling those fails building as it looks like
>
> Correction: DM_USB conversion is due to 2019.07 release.
>
> > these DM drivers expect OF_CONTROL (U-Boot running from a
> > device-tree). Is that currently true or am I perhaps missing
> > something? I haven't pinned down what exactly is missing yet so I
>
> That's correct.
>
> > thought I would ask. It looks like only a couple of IMX6 boards have
> > been converted over thus far.
>
> You can also take a look at the patch series from Abel that converts
> mx6sabreauto/sabresd boards to DM:
> http://git.denx.de/?p=u-boot/u-boot-imx.git;a=shortlog
>
> > What is the IMX6 status of DM_SCSI/DM_PCI/DM_VIDEO which are required
> > by v2019.07?
>
> As far as I know these are not done yet.
>

Fabio / Stefano,

Thanks for your quick response. Yes, I've been looking at the
mx6sabreauto conversion series and trying to plot a course for my
boards that won't completely thrash users - we need backwards
compatibility.

We currently have a large list of IMX6 boards with different dtbs
(about 10 boards in total resulting in 20 dtbs b/c of the imx6q vs
imx6dl options). These currently are all covered by a single
SPL/U-Boot binary of board/gateworks/gw_ventana and not using
OF_CONTROL (as its relatively new for IMX6 and these boards have been
around for many years now). Boot scripts are setup to load the DTB
from the root filesystem which varies per OS between a ubi volume or
ext filesytem.

So it looks like what I need to do is add all my device-tree's from
the kernel to U-Boot's arch/arm/dts, add SPL_MULTI_DTB_FIT support and
a board_fit_config_name_match() function for the SPL to pick the right
DTB. Some questions come to mind:

1. Where would I apply any fixup's to the DTBs before they are used by the SPL?

2. I'm assuming the FIT image is embedded within the SPL and thus does
not require specific storage/filesystem support?

3. Users are used to being able to update the DTB's used by Linux by
updating them on the filesystem - does all of this give the user the
option of using either the DTB that U-Boot uses vs the DTB that
already exists on one of the partitions? If the bootscripts already
load a DTB from a filesystem does U-Boot's ft_board_setup() still
function normally?

Regards,

Tim