[U-Boot] [PATCH] jetson-tk1: Set fdtfile environment variable

[Andreas Färber]

Am 13.04.2016 um 17:31 schrieb Stephen Warren:
> On 04/13/2016 06:55 AM, Andreas Färber wrote:
>> Am 13.04.2016 um 14:48 schrieb Andreas Färber:
>>> The 4.5.0 kernel cannot cope with U-Boot's internal device tree, and the
>>> distro boot commands are looking for $fdtfile, so provide it to avoid
>>> having users supply a dumb boot.scr doing a setenv fdtfile ...; boot,
>>> defeating the purpose of generic EFI boot.
>>>
>>> Cc: Stephen Warren <swarren at nvidia.com>
>>> Cc: Alexander Graf <agraf at suse.de>
>>> Signed-off-by: Andreas Färber <afaerber at suse.de>
>>> ---
>>>   include/configs/jetson-tk1.h | 4 ++++
>>>   1 file changed, 4 insertions(+)
>>>
>>> diff --git a/include/configs/jetson-tk1.h b/include/configs/jetson-tk1.h
>>> index 59dbb20..82a4be4 100644
>>> --- a/include/configs/jetson-tk1.h
>>> +++ b/include/configs/jetson-tk1.h
>>> @@ -63,6 +63,10 @@
>>>   /* General networking support */
>>>   #define CONFIG_CMD_DHCP
>>>
>>> +#define BOARD_EXTRA_ENV_SETTINGS \
>>> +    "fdtfile=tegra124-jetson-tk1.dtb\0" \
>>> +    ""
>>
>> Is there any more intelligent solution than doing this for each board?
> 
> Yes, the distro boot scripts shouldn't be using $fdtfile unconditionally
> since it's not guaranteed to be set. The model is that boot scripts
> determine the FDT filename, and $fdtfile is an optional override.
> 
> It looks like the hard-coded use of $fdtfile was added into the EFI
> path, which I didn't get to review, and which shouldn't be enabled by
> default but unfortunately is.

As Alex described, you're entirely missing the point here.

The EFI bootloader is an alternative to a board-specific script, not an
addition. The loading logic is all in the U-Boot environment and it
needs to know what device tree to use without the user telling it:

a) master branch searches for $fdtfile in various prefixes on the
current boot device partition.

a') We're testing a variation where we load $fdtfile from a different
partition on the same device (i.e., from ext4/btrfs rather that fat).

b) A pending patch exposes the internal U-Boot device tree.

The former is what we need to boot today. For openSUSE we get the .dtb
files from rpm packages built from the kernel.

The latter would match the Tianocore/Aptio model where all board info
comes from the firmware exclusively. As reported elsewhere it does not
yet work on this board with your DT though; you yourselves discussed
about differing cell sizes and node names.

Now during my EFI testing I had to repeatedly remember to interrupt
U-Boot and type:

setenv fdtfile tegra124-jetson-tk1.dtb
boot

until I got so annoyed that I figured out this patch to make it permanent.

The hikey and some other boards got their variable renamed to fit
standardized $fdtfile, for dragonboard410c I sent a similar patch.

My above question was more precisely: Can we automate supplying the
$fdtfile at tegra124-common.h or tegra-common.h level instead of as in
this patch manually at jetson-tk1.h level where I happened to notice?

The Raspberry Pi has been supplying $fdtfile just fine (modulo the rev
B), so I don't understand why you'd be against it now.

Thanks,
Andreas

P.S. Without a standardized $fdtfile you can't have a standard boot.scr
either, so the generic mechanism becomes moot.

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