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

Fri Dec 30 20:12:38 CET 2022

On Friday 30 December 2022 12:51:03 Simon Glass wrote:
> Hi Pali,
> 
> On Fri, 30 Dec 2022 at 11:55, Pali Rohár <pali at kernel.org> wrote:
> >
> > 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.
> 
> OK, we can do that I suppose, perhaps with a new binman property:
> 
> u_boot: u-boot-nodtb {
> };
> u-boot-dtb {
>    align-to-sym = <&u_boot> ,"_end";
> };
> 
> or using expanding just:
> 
> u-boot {
>    align-dtb-to-sym = <&u_boot> ,"_end";
> };
> 
> (which we could perhaps make the default?)

Something like that looks reasonable. And must be enabled by default.

I'm not sure if calling it "align" is a good idea. Because if property
is in u-boot node then it it is "padding". And if that property is in
dtb node then it is "placing" binary to the absolute address.

>From reading binman.html documentation I see that for placing image at
absolute address there is already "offset" property. And for padding
there is "pad-after" property. What about consistency?

So maybe 'pad-after-to-sym = "_end";' in u-boot node?
Or 'offset-from-sym = <&u_boot>, "_end";' in dtb node?

> >
> > > 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).
> 
> We changed this 6 years ago and I'm not keen on going back.
> 
> ad1ecd2063d fdt: Build a U-Boot binary without device tree

I just do not understand you because in that commit is exactly what I
wrote. In file u-boot-dtb.bin is u-boot binary with DTB and in file
u-boot-nodtb.bin is u-boot binary without DTB.

So binman should take input files u-boot-nodtb.bin and DTB binary. And
should produce output file u-boot-dtb.bin. Is there any issue with it?

> >
> > > 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.
> 
> Regards,
> Simon
> 
> 
> [1] https://u-boot.readthedocs.io/en/latest/develop/package/binman.html#expanded-entries