[U-Boot] [PATCH] configs: Remove CONFIG_SPL_FS_EXT4 for all MX6 platforms

[Lukasz Majewski <lukma@denx.de>]

Dear Marek, Tom,

> On 5/26/19 1:23 AM, Tom Rini wrote:
> > On Sun, May 26, 2019 at 01:20:34AM +0200, Marek Vasut wrote:  
> >> On 5/26/19 1:08 AM, Tom Rini wrote:  
> >>> On Sun, May 26, 2019 at 12:57:08AM +0200, Marek Vasut wrote:  
> >>>> On 5/26/19 12:45 AM, Ezequiel Garcia wrote:  
> >>>>> On Sun, 2019-05-26 at 00:24 +0200, Marek Vasut wrote:  
> >>>>>> On 5/25/19 11:47 PM, Ezequiel Garcia wrote:  
> >>>>>>> On Sat, 2019-05-25 at 22:15 +0200, Marek Vasut wrote:  
> >>>>>>>> On 5/25/19 6:49 PM, Ezequiel Garcia wrote:  
> >>>>>>>>> i.MX6 platforms boot U-Boot second-stage from unformatted
> >>>>>>>>> space, and should not need Ext filesystem support on SPL.
> >>>>>>>>>
> >>>>>>>>> The commit was generated with:
> >>>>>>>>>
> >>>>>>>>> git grep -l MX6 -- configs/ | xargs grep -l SPL_FS_EXT4 |
> >>>>>>>>> xargs sed -i -e '/CONFIG_SPL_FS_EXT4=y/d'
> >>>>>>>>>
> >>>>>>>>> This change has a dramatic impact on SPL size:
> >>>>>>>>>
> >>>>>>>>> ./scripts/bloat-o-meter old new
> >>>>>>>>> add/remove: 0/59 grow/shrink: 0/3 up/down: 0/-8674 (-8674)
> >>>>>>>>> [..]
> >>>>>>>>> Total: Before=38320, After=29646, chg -22.64%
> >>>>>>>>>
> >>>>>>>>> Cc: Otavio Salvador <otavio@ossystems.com.br>
> >>>>>>>>> Cc: Fabio Estevam <fabio.estevam@nxp.com>
> >>>>>>>>> Cc: Peng Fan <peng.fan@nxp.com>
> >>>>>>>>> Cc: Marek Vasut <marex@denx.de>
> >>>>>>>>> Cc: Stefano Babic <sbabic@denx.de>
> >>>>>>>>> Cc: Stefan Roese <sr@denx.de>
> >>>>>>>>> Cc: "Eric Bénard" <eric@eukrea.com>
> >>>>>>>>> Cc: Breno Lima <breno.lima@nxp.com>
> >>>>>>>>> Cc: Francesco Montefoschi <francesco.montefoschi@udoo.org>
> >>>>>>>>> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> >>>>>>>>> ---
> >>>>>>>>> Tested on Wandboard only. Maintainers, please ACK or NAK!
> >>>>>>>>>
> >>>>>>>>>  configs/cgtqmx6eval_defconfig       | 1 -
> >>>>>>>>>  configs/mx6cuboxi_defconfig         | 1 -
> >>>>>>>>>  configs/mx6sabreauto_defconfig      | 1 -
> >>>>>>>>>  configs/mx6sabresd_defconfig        | 1 -
> >>>>>>>>>  configs/mx6slevk_spl_defconfig      | 1 -
> >>>>>>>>>  configs/mx6sxsabresd_spl_defconfig  | 1 -
> >>>>>>>>>  configs/mx6ul_14x14_evk_defconfig   | 1 -
> >>>>>>>>>  configs/mx6ul_9x9_evk_defconfig     | 1 -
> >>>>>>>>>  configs/novena_defconfig            | 1 -  
> >>>>>>>>
> >>>>>>>> NAK, I boot my Novena from ext4 and this just broke it.
> >>>>>>>>
> >>>>>>>> And also, NAK, this removes functionality from SPL which
> >>>>>>>> worked fine before. 
> >>>>>>>
> >>>>>>> I'll drop from Novena, but I think the patch still makes some
> >>>>>>> sense, why do you want Ext4 on SPL?  
> >>>>>>
> >>>>>> What other filesystem is available in SPL and doesn't have
> >>>>>> patent problems ? 
> >>>>>
> >>>>> Sorry for not being clear. I am asking why turn on a feature
> >>>>> that is so heavy, on a system that won't need it (such as
> >>>>> Sabre* boards, Wandboard and similar)?  
> >>>>
> >>>> Two reasons:
> >>>> 1) It was enabled, disabling it means removing functionality for
> >>>> no good reason (oops, bloat, is not a good reason), and that is
> >>>> not desired. 2) Booting from block device implies booting from a
> >>>> filesystem, otherwise you might overwrite various things on the
> >>>> block device when updating the file (u-boot image).  
> >>>
> >>> So, are you using SPL to load something from ext4 or not?  
> >>
> >> Yes, I think that's what I said.
> >>  
> >>> There are
> >>> setups where people have configured the system such that SPL loads
> >>> something from ext4 and that's why we have it available.  Is
> >>> anyone doing that on Novena?  Or any iMX system?  
> >>
> >> Quoting my first response in this thread:
> >> "
> >> NAK, I boot my Novena from ext4 and this just broke it.
> >> "  
> > 
> > Actually, I wasn't sure from your first response if you're using
> > SPL to load u-boot from EXT4 or not.  So, Novena is a no and we
> > should wait for more board maintainers to speak up to see if they
> > use it or not, thanks!  
> 
> Novena is certainly a no. Since I use a couple of wandboards, those
> are no as well.
> 
> But I do not want to see useful functionality removed from SPL only to
> make space for useless DM/DT bloat. Temporarily band-aiding this real
> problem by removing functionality is a no-go, no matter how you slice
> it. The real fix is to fix the DM/DT and figure out a way to reduce
> it's size and _retain_ _all_ the functionality.
> 

I fully agree with Marek here - the DM/DT SPL support (in the form as
it is now) is a bloat. The SPL size increases considerably.

The _real_ issue is the lack of OF_PLATDATA support for DM/DTS drivers,
which are used when we convert u-boot to DM/DTS.

For boards, which have enough internal on-chip RAM (OCRAM in case of
imx6q) it is doable to convert them to DM/DTS in SPL.

However, nobody wants to say it loud, but the footprint considerably
increases in SPL - for example:

SPL (and I only use eMMC there - no SPI, no I2C):
------------------------------------------------
Before conversion:                              35 KiB
DM conversion:					47 KiB
(around ~25% increase)


For u-boot proper:
----------------------------
Footprint changes (u-boot.imx):

Before conversion:                              345 KiB
DM conversion:                    415 KiB
(around + 17% increase)


This has several implications:

1. We replace small, robust SPL (I speak only for i.MX) with something
which is XX% larger and hence boot time increases. In short - customers
are/will not be happy. We do introduce regression here.

2. To make it usable (with the size comparable to what we do have now)
we need to add OF_PLATDATA support to eMMC, SPI, I2C, etc. drivers. Test
them and validate.

That is why we now "just" convert only U-Boot proper to DM/DTS. 

As a follow up - it seems pragmatic to not touch SPL for now, and start
the conversion ONLY when necessary drivers gain support for OF_PLATDATA
(so we don't need DTS support in SPL).

Unfortunately, it would take some time.


Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
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Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma at denx.de
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