[U-Boot] [PATCH 2/2] board: tbs2910: Remove FIT support in defconfig to reduce u-boot size

[Soeren Moch]

On 09.01.19 23:39, Tom Rini wrote:
> On Wed, Jan 09, 2019 at 05:01:37PM +0100, Stefano Babic wrote:
>> Hi Soeren,
>>
>> On 08/01/19 12:03, Soeren Moch wrote:
>>> Hi Stefano,
>>>
>>> On 08.01.19 11:24, Stefano Babic wrote:
>>>> Hi Soeren,
>>>>
>>>> On 08/01/19 11:14, Soeren Moch wrote:
>>>>> Stefano,
>>>>>
>>>>> can you apply this for v2019.01? This is really a important fix to avoid
>>>>>  environment and u-boot binary overwriting each other.
>>>>> It is also a small local fix which cannot hurt anybody else.
>>>> I will apply and I send a new PR. This is not the first fix in this
>>>> direction, u-boot becomes pretty large, it is becoming a common problem.
>>>>
>>> Thank you very much.
>>>
>>> Yes, "in the good old days (tm)" there was much effort put into not
>>> increasing the binary size for existing boards when adding new features.
>> Right, fully agree.
>>
>>> Unfortunately this is not true anymore.
>> I get in the same trouble with more as one project. A previous rule of
>> thumb was to reserve 512KB to the bootloader because it was pretty
>> unthinkable that bootloader could be larger. Mhmmhh....this remember me
>> someone else who said that 640Kb is enough for everything.
>>
>> Anyway, as you noted, this is a big problem in field and it makes
>> difficult an upgrade without returning back the device to factory, what
>> nobody wants.
> So, this is more on me, so I should probably explain a little, and point
> at the biggest culprit too.  The biggest at times culprit and sometimes
> controversial thing is that we default to the EFI subsystem being on by
> default.  This is 50KiB on tbs2910.  Why default?  Well, "everyone"
> agrees that defaulting to EFI application support means the widest
> choice of out of the box software support.
>
Hm, AFAIK EFI support is very uncommon for arm32, at least for pre-arm64
boards. The usual way for firmware updates was to load a special
UEnv.txt or boot.scr with commands. But OK, maybe it is more modern or
more convenient these days to support EFI, maybe a good idea to
default=y, but why this is not disabled in old board's defconfigs then?
Either "automatically" like in the Kconfig conversions, or via a short
notice to the relevant board maintainers?
I also noticed this EFI support as big, but disabling it is more
complicated than disabling FIT, and we are at -rc3. Maybe I will send a
corresponding patch for the next merge window.
> And I do look at size changes, at least per push to master.  So most of
> the time it comes in "drips and drabs".  Right now I'm going to grow
> tbs2910 by 60 bytes[1].  Most of that is section re-alignment and 8 of it
> is the regression fix to mmc_startup() or non-DM MMC drivers.  But
> that's not super interesting, so lets look at v2018.09 to now.  That's
> 1800 bytes.  That's not too bad and looks like it's maybe half bug
> fixes, half working on various frameworks (sure, DM/DT stuff but also
> hash algos.  If we jump back to v2018.01, so more or less a year worth
> of changes, that's 19KiB.  Without trying to break down _everything_
> that's a good bit of EFI and a little bit everywhere else.
I fully understand that this is not a easy job for you. And usually a
few kiB are not a big deal. But the one kiB that overwrites the
environment on eMMC (and therefore often bricks the board) is very very
inconvenient for users.
>>> And all the shiny new driver model / OF features only bring
>>> disadvantages for maintainers and users of existing boards.
>>>
>>> I totally understand the desire to convert the driver code to "something
>>> better", which is easier to maintain long-term. But apparently new code
>>> is only tested on a single platform, while constantly breaking support
>>> for others without notice. But 'm complaining to the wrong person...
>> Yes, I am not the right person ;-)
>>
>> I picked up your patches, I will run build tests and if everything is
>> fine I will sent PR for 2019.01.
> In retrospect, I wish more people knew about enforcing a link time hard
> limit on the binary and knew about it a lot longer ago.  Because when
> those failures pop up, I don't apply the new PR and I start talking to
> the relevant parties to see what we can do.
Unfortunately I learned about the availability of this check only
recently. As hobbyist maintainer I usually rely on the reference board
settings.


But for v2019.01 all the problems (MMC partitions and u-boot size) have
been solved (when the relevant patches are applied), so I think we are
in good shape for now.

The bigger challenge are the BLK and DM conversions for the next u-boot
version. I absolutely cannot understand how somebody can insist on these
changes, while letting the board maintainers completely alone with
required driver adaptations. Board maintainers are not familiar with
driver code, a lot of board maintainers would need to work in parallel
on this (when no person is designated for this work, all maintainers are
equally responsible), while the author of the BLK/DM core code is very
familiar with the required changes. The necessary API adaptations in
drivers would be a no-brainer for him, since nothing of the actual
hardware access code needs to be adapted. At least that is my understanding.
But someone (who actually?) decided to simply offload the second
conversion step (drivers) to somebody else, with no help offered for
this, but with short deadlines. I never heard that this can work in
community projects.
If the driver adaptations are done for a single board from each family,
then the third step (adapting board configurations) is a job for board
maintainers. But we're not at his point.

I can offer to help with testing for adapted mmc, usb, and sata drivers
for the imx6qdl family. But I will not do the driver conversions myself.

Regards,
Soeren

> [1]: buildman --step 0 -SBCdevlk followed by --step 0 -SsBdevlk to see
> how much and where, and yes, that's a few more flags than I _need_ for
> that, and since it's in a script I never go and optimize it down.
>