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

[Stephen Warren]

On 04/13/2016 09:51 AM, Alexander Graf wrote:
> On 04/13/2016 05:31 PM, Stephen Warren wrote:
>> 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.
>
> The point of all of the efi magic is that we can completely get rid of
> boot scripts. Boards use the distro scripts, everything else gets
> implicitly detected and executed. The way other boards deal with common
> code mapping into separate boards is to either implement a "findfdt"
> scriptlet or directly write the fdtfile variable (e.g. beaglebone) in
> board init (e.g. rpi).
>
>> 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.
>
> s/un// :)
>
> Just imagine a world where people don't have to worry about bootloaders
> anymore. Things would "just work". You plug in a usb stick, it comes up,
> boots Linux, everthing goes without anyone touching boot scripts,
> downloading board specific files, etc. You could get a random
> distribution from a common download page from somewhere and just run it.
>
> Well, you can also just look at any random x86 system. They get at least
> that part pretty right these days.

Well, you can also get the same benefit using extlinux.conf, and without 
relying on EFI:-P

Anyway, nothing in your benefits-of-EFI statement implies that relying 
on $fdtfile being set is correct. That's a new requirement that didn't 
exist before. Either the requirement needs to be removed (e.g. using a 
default FDT filename such as "${soc}-${board}${boardver}.dts") or only 
enabling this functionality on boards that do set $fdtfile, since it 
relies on that.