[PATCH u-boot 2/2] Makefile: Build working u-boot-dtb.bin target also for mpc85xx

[Pali Rohár]

On Friday 30 December 2022 11:43:44 Simon Glass wrote:
> Hi Pali,
> 
> On Fri, 30 Dec 2022 at 10:06, Pali Rohár <pali at kernel.org> wrote:
> >
> > On Friday 30 December 2022 09:49:08 Simon Glass wrote:
> > > Hi Pali,
> > >
> > > On Fri, 30 Dec 2022 at 09:44, Pali Rohár <pali at kernel.org> wrote:
> > > >
> > > > On Friday 30 December 2022 10:41:47 Tom Rini wrote:
> > > > > On Fri, Dec 30, 2022 at 04:24:43PM +0100, Pali Rohár wrote:
> > > > > > On Friday 30 December 2022 10:21:04 Tom Rini wrote:
> > > > > > > > In this case it would be better to build u-boot-dts.bin only by binman
> > > > > > > > (for all platforms) instead of cat-ing rules in Makefile.
> > > > > > >
> > > > > > > This would also be an easier path forward perhaps for making sure that
> > > > > > > the dtb is always 8 byte aligned?
> > > > > >
> > > > > > Well, no. With DTB the problem is that it is not put to the correct
> > > > > > offset as can be specified in linker script. So moving this code from
> > > > > > Makefile to binman also moves this problem to another location.
> > > > > > 8 byte alignment is just subset of the "correct offset" problem.
> > > > >
> > > > > Right, the high level answer is binman is intended to be the tool to
> > > > > assemble binaries, and has to deal with "make sure binary X is at offset
> > > > > Y, which also has a linker symbol for run-time references".
> > > >
> > > > Ok, if this tool has access to ELF/linker symbols (or will have in
> > > > future in case it does not have yet) then this problem could be solved
> > > > here.
> > >
> > > It does have this access and already updates symbols in some cases.
> > > See [1].
> > > [1] https://u-boot.readthedocs.io/en/latest/develop/package/binman.html#access-to-binman-entry-offsets-at-run-time-symbols
> >
> > I just do not see how to do it, but ok, maybe something more is needed.
> >
> > > I am a little nervous about a complete move to binman in this
> > > area even for simple things like u-boot.bin, since it would set off
> > > yet another migration.
> >
> > Yes, it sounds like a big change.
> >
> > > But perhaps most boards don't actually use u-boot.bin anyway?
> >
> > I think that most boards _use_ u-boot.bin. Or wrap u-boot.bin into some
> > own container (by mkimage).
> >
> > > Part of me thinks we should solve this in the .lds files, since
> > > otherwise we are blurring the line between building and packaging.
> >
> > Linker script files in any case would have to be adjusted / fixed to
> > align _end symbol. Without it ELF symbol would not be correct and so
> > obviously any solution depending on ELF symbols would not work...
> >
> > As I wrote recently, I proposed alternative solution without binman:
> > https://lore.kernel.org/u-boot/20221217235913.w7ihsktbplbp2j7z@pali/
> 
> I think that would work. It is a little like the BINARY_SIZE_CHECK
> thing we have. It is the closest thing to what we have. As you saw I
> was happy with your original 'trunc' solution too.
> 
> After some more thought, perhaps the binman solution makes sense, so
> long as we do what you say above (make the _end symbol aligned). Of
> course binman can fix that up, but it feels more like a build thing
> than a packaging thing to me.

Yes, this is build thing/issue, not packaging one.

> It could be quite confusing for people
> to see a symbol change between build-time and run-time.

Yes, symbol change is confusing. So I would propose to not change any
symbol between build and run time.

> So the steps would be something like this:
> 
> 1. Update the align before _end in each .lds to use a constant like
> #define END_ALIGN  8
> 2. Update binman's dtb etypes to align to 8 bytes

This is not enough. Some boards/platform may have stricter alignment
(e.g. to SD card sector size = 512 bytes). So binman should not align
image and instead of that, it should read _exact_ address of _end
symbol and put DTB etype to this address. Step 1. already ensures that
_end is aligned to 8 bytes.

> 3. Add a common binman image for u-boot.bin (used by every board)

It should be u-boot-dtb.bin (not u-boot.bin). At least this is the
current file name. (See this my patch series again, which aligns this
naming also for powerpc/mpc85xx).

> 4. Enable binman by default
> 5. Drop the current 'cat' rules in Makefile, so that only u-boot and
> u-boot-nodtb.bin are produced

(cat rule is only for u-boot-dtb.bin)

> 6. Optionally consider moving .img files to binman also
> 
> Regards,
> Simon

With slightly modified/improved step 2. I agree that this improves
current situation. And should these issues.