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

[Tomasz Figa]

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.

Best regards,
-- 
Tomasz Figa
Samsung Poland R&D Center
SW Solution Development, Linux Platform