[PATCH] ARM: dts: add board dts file for Exynos4412 based SMDK board

[Tomasz Figa]

On Friday 16 of November 2012 18:47:54 Thomas Abraham wrote:
> On 16 November 2012 18:28, Tomasz Figa <t.figa at samsung.com> wrote:
> > On Friday 16 of November 2012 18:03:15 Thomas Abraham wrote:
> >> On 16 November 2012 16:41, Tomasz Figa <t.figa at samsung.com> wrote:
> >> > On Thursday 15 of November 2012 13:48:55 Thomas Abraham wrote:
> >> >> Hi Tomasz,
> >> >> 
> >> >> Thanks for your comments.
> >> >> 
> >> >> On 12 November 2012 19:37, Tomasz Figa <t.figa at samsung.com> wrote:
> >> >> > Hi Thomas,
> >> >> > 
> >> >> > On Saturday 03 of November 2012 20:19:32 Thomas Abraham wrote:
> >> >> >> Add a minimal board dts file for Samsung Exynos4412 based SMDK
> >> >> >> board.
> >> >> >> 
> >> >> >> Signed-off-by: Thomas Abraham <thomas.abraham at linaro.org>
> >> >> >> ---
> >> >> >> This patch depends the on the following patch posted by Tomasz
> >> >> >> Figa.
> >> >> >> "ARM: dts: exynos4: Add support for Exynos4x12 SoCs"
> >> >> >> 
> >> >> >>  arch/arm/boot/dts/Makefile                |    1 +
> >> >> >>  arch/arm/boot/dts/exynos4412-smdk4412.dts |   45
> >> >> >> 
> >> >> >> +++++++++++++++++++++++++++++ 2 files changed, 46 insertions(+),
> >> >> >> 0
> >> >> >> deletions(-)
> >> >> >> 
> >> >> >>  create mode 100644 arch/arm/boot/dts/exynos4412-smdk4412.dts
> >> >> >> 
> >> >> >> diff --git a/arch/arm/boot/dts/Makefile
> >> >> >> b/arch/arm/boot/dts/Makefile
> >> >> >> index f37cf9f..36488a5 100644
> >> >> >> --- a/arch/arm/boot/dts/Makefile
> >> >> >> +++ b/arch/arm/boot/dts/Makefile
> >> >> >> @@ -23,6 +23,7 @@ dtb-$(CONFIG_ARCH_DOVE) += dove-cm-a510.dtb \
> >> >> >> 
> >> >> >>  dtb-$(CONFIG_ARCH_EXYNOS) += exynos4210-origen.dtb \
> >> >> >>  
> >> >> >>       exynos4210-smdkv310.dtb \
> >> >> >>       exynos4210-trats.dtb \
> >> >> >> 
> >> >> >> +     exynos4412-smdk4412.dtb \
> >> >> >> 
> >> >> >>       exynos5250-smdk5250.dtb
> >> >> >>  
> >> >> >>  dtb-$(CONFIG_ARCH_HIGHBANK) += highbank.dtb
> >> >> >>  dtb-$(CONFIG_ARCH_INTEGRATOR) += integratorap.dtb \
> >> >> >> 
> >> >> >> diff --git a/arch/arm/boot/dts/exynos4412-smdk4412.dts
> >> >> >> b/arch/arm/boot/dts/exynos4412-smdk4412.dts new file mode 100644
> >> >> >> index 0000000..f05bf57
> >> >> >> --- /dev/null
> >> >> >> +++ b/arch/arm/boot/dts/exynos4412-smdk4412.dts
> >> >> >> @@ -0,0 +1,45 @@
> >> >> >> +/*
> >> >> >> + * Samsung's Exynos4412 based SMDK board device tree source
> >> >> >> + *
> >> >> >> + * Copyright (c) 2012-2013 Samsung Electronics Co., Ltd.
> >> >> >> + *           http://www.samsung.com
> >> >> >> + *
> >> >> >> + * Device tree source file for Samsung's SMDK4412 board which
> >> >> >> is
> >> >> >> based
> >> >> >> on + * Samsung's Exynos4412 SoC.
> >> >> >> + *
> >> >> >> + * This program is free software; you can redistribute it
> >> >> >> and/or
> >> >> >> modify + * it under the terms of the GNU General Public License
> >> >> >> version 2 as + * published by the Free Software Foundation.
> >> >> >> +*/
> >> >> >> +
> >> >> >> +/dts-v1/;
> >> >> >> +/include/ "exynos4412.dtsi"
> >> >> >> +
> >> >> >> +/ {
> >> >> >> +     model = "Samsung SMDK evaluation board based on
> >> >> >> Exynos4412";
> >> >> >> +     compatible = "samsung,smdk4412", "samsung,exynos4412";
> >> >> >> +
> >> >> >> +     memory {
> >> >> >> +             reg = <0x40000000 0x40000000>;
> >> >> >> +     };
> >> >> > 
> >> >> > This will not boot, because section size limit is set to 256 MiB.
> >> >> > 
> >> >> > It might work with CONFIG_ARM_ATAG_DTB_COMPAT enabled, because
> >> >> > the
> >> >> > memory configuration from DT is ignored and values from ATAGs are
> >> >> > taken instead.
> >> >> > 
> >> >> > I suggest you to change it to 4 banks of 256 MiB.
> >> >> 
> >> >> Thanks for pointing this out. So are there any existing exynos
> >> >> based
> >> >> platforms that use sparse mem? If not, we should probably remove
> >> >> the
> >> >> section length configuration itself for mach-exynos. I suspect this
> >> >> setting might not help with the single kernel image support as
> >> >> well.
> >> > 
> >> > Isn't sparse memory the only configuration available for
> >> > ARCH_EXYNOS?
> >> 
> >> Yes, true. Since sparsemem is choosen as default for Exynos, flatmem
> >> option is not available. Theoretically, sparsemem could be used on
> >> Exynos platforms, but if all existing exynos4/5 based boards have no
> >> holes in memory, then why not use flatmem instead? If there are
> >> performance benefits of using flatmem over sparesmem on systems
> >> without any memory holes, then it is a compelling reason to stop using
> >> sparsemem on Exynos. But then, what if there is a new Exynos4/5 based
> >> board that comes up and that has a memory hole? Or, how about removing
> >> sparsemem as default option for ARCH_EXYNOS and enabling sparsemem for
> >> boards that need it.
> > 
> > I'm not sure about any significant performance benefits of FLATMEM over
> > SPARSEMEM. Some ancient benchmark from 2007 shows that overhead level
> > of
> > both is similar.
> > 
> > You can find the benchmark here:
> > http://lkml.indiana.edu/hypermail/linux/kernel/0711.1/1239.html
> > 
> > I think we should leave it as is for the time being and just make sure
> > that sections of boards are defined according to section size limit.
> 
> Ok, makes sense. Thanks. By the way, I was checking why this patch did
> not lead me to a crash as you described. u-boot seems to be overriding
> the memory node in the dts file and creating a new memory node with
> the memory banks information that u-boot has. So looking at
> /proc/device-tree/memory/reg, there are multiple 256MB sized entries
> there.

OK, it seems like you are using a DT-aware u-boot. It can generate memory 
and chosen nodes, so I guess the behavior you observe is fine.

I'm testing on a legacy u-boot version without DT support, so all the 
information must be included in the appended DTB and so I observed boot 
crashes with too big sections.

Btw. It seems like Kgene has already applied your patch, so let's send a 
separate fixup patch. It can be considered a fix so there shouldn't be any 
problems with merging it. Should I send it or you will do it?

Best regards,
Tomasz Figa