linux-kernel - Re: [PATCH] of: build dbts with symbols when CONFIG_OF

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Message-ID: <05291157-a1dc-db84-e453-c43945c1da07@gmail.com>
Date:   Sat, 16 Dec 2017 18:25:33 +0100
From:   Andre Heider <a.heider@...il.com>
To:     Frank Rowand <frowand.list@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>
Cc:     linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] of: build dbts with symbols when CONFIG_OF_OVERLAY is set

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@...il.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.

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