Subject: Re: [PATCH] of: build dbts with symbols when CONFIG_OF_OVERLAY is set
To: Andre Heider <a.heider@gmail.com>, Rob Herring <robh+dt@kernel.org>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Michal Marek <michal.lkml@markovi.net>
Cc: linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
References: <20171214151240.14555-1-a.heider@gmail.com>
From: Frank Rowand <frowand.list@gmail.com>
Message-ID: <aada8c54-2c26-bf37-8782-4edc43195daf@gmail.com>
Date: Fri, 15 Dec 2017 13:06:56 -0800
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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@gmail.com>
> ---
> 
> 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.

-Frank