Re: [PATCH] of: build dbts with symbols when CONFIG_OF_OVERLAY is set

[Andre Heider]

Hi Frank,

On 15/12/17 22:06, Frank Rowand wrote:
> On 12/14/17 07:12, Andre Heider wrote:
> > The overlay feature requires the base dtb to be built with symbols, so
> > lets build the dtbs with symbols when overlay support was explicitly
> > enabled.
> >
> > With CONFIG_OF_ALL_DTBS on ARCH=arm the 989 dtb files grow about ~38% on
> > average.
> >
> > Totals in bytes with the 3 biggest ones:
> >
> > Before:
> > 	90471	arch/arm/boot/dts/am57xx-beagle-x15-revc.dtb
> > 	90521	arch/arm/boot/dts/am57xx-beagle-x15-revb1.dtb
> > 	92639	arch/arm/boot/dts/dra7-evm.dtb
> > 	25731296	total
> >
> > After:
> > 	133203	arch/arm/boot/dts/am57xx-beagle-x15-revc.dtb
> > 	133237	arch/arm/boot/dts/am57xx-beagle-x15-revb1.dtb
> > 	134545	arch/arm/boot/dts/dra7-evm.dtb
> > 	35464440	total
> >
> > Signed-off-by: Andre Heider <a.heider@xxxxxxxxx>
> > ---
> >
> > Hi,
> >
> > while playing around with overlays I noticed that I needed to rebuilt
> > my distro's device trees because they didn't come with symbols.
> >
> > Is that for a reason, maybe the not so minor increase in size?
>
> Yes, size is the issue.
>
>
> > Thanks,
> > Andre
> >
> >   drivers/of/unittest-data/Makefile | 7 -------
> >   scripts/Makefile.lib              | 5 +++++
> >   2 files changed, 5 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/of/unittest-data/Makefile b/drivers/of/unittest-data/Makefile
> > index 32389acfa616..b65061013512 100644
> > --- a/drivers/of/unittest-data/Makefile
> > +++ b/drivers/of/unittest-data/Makefile
> > @@ -15,13 +15,6 @@ targets += overlay.dtb overlay.dtb.S
> >   targets += overlay_bad_phandle.dtb overlay_bad_phandle.dtb.S
> >   targets += overlay_bad_symbol.dtb overlay_bad_symbol.dtb.S
> >   targets += overlay_base.dtb overlay_base.dtb.S
> > -
> > -# enable creation of __symbols__ node
> > -DTC_FLAGS_overlay := -@
> > -DTC_FLAGS_overlay_bad_phandle := -@
> > -DTC_FLAGS_overlay_bad_symbol := -@
> > -DTC_FLAGS_overlay_base := -@
> > -
> >   endif
> >   
> >   .PRECIOUS: \
>
> No.  The unittests require these to be set unconditionally.
>
>
> > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> > index 1ca4dcd2d500..c7ba4aa8a07a 100644
> > --- a/scripts/Makefile.lib
> > +++ b/scripts/Makefile.lib
> > @@ -278,6 +278,11 @@ DTC_FLAGS += -Wnode_name_chars_strict \
> >   	-Wproperty_name_chars_strict
> >   endif
> >   
> > +ifeq ($(CONFIG_OF_OVERLAY),y)
> > +# enable creation of __symbols__ node
> > +DTC_FLAGS += -@
> > +endif
> > +
> >   DTC_FLAGS += $(DTC_FLAGS_$(basetarget))
> >   
> >   # Generate an assembly file to wrap the output of the device tree compiler
>
> Not needed.  Instead set DTC_FLAGS in the make command.  For example:
>
>     DTC_FLAGS=-@ make qcom-apq8074-dragonboard.dtb
>
> There are a few architecture Makefiles that need to be fixed to not unconditionally
> set DTC_FLAGS.

Rebuilding the dts files manually with symbols isn't the problem. The 
idea was to enable it with a switch which distros simply can flip.

Passing DTC_FLAGS to `make` would work too I guess, but on multi 
platform builds that's still the same issue if there're boards which 
can't handle that because of the size increase.

Would a solution which enables symbols per family work?
E.g. CONFIG_MACH_SUN7I chooses to use -@ because it can handle it.

Thanks,
Andre