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

[Adam Ford]

On Tue, Feb 19, 2019 at 1:11 PM Tim Harvey <tharvey at gateworks.com> wrote:
>
> 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.

DM_USB creates an SPL binary that's fairly large.  There is an option
to leave SPL_DM_USB off, is that going to be an issue?  I know people
want to move away from the older code, but the DM overhead makes it
really difficult to fit evertyhing.  I've got an i.MX6 board with NAND
and SD cards.  I use the USB to load a blank or erased SOM, which
requires some overhead, but it appears to work with SPL_DM_USB
disabled.  Because of the overhead for DM_MMC, and NAND (which
requires some DMA stuff), I am having a hard time getting
SPL_OF_CONTROL to fit into the required space.

I think it would be really nice if supporting OF_PLATDATA was required
in order to reduce the overhead of devices with small SPL space, but
it requires some reworking of the drivers to support his.

> >
> > > 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.

There seems to be something broken when booting from NAND if SPL_DM
and SPL_OF_CONTROL are both enabled too.

adam
> >
>
> 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
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