[U-Boot] [PATCH 0/7] Exynos4412 SPL support

[Simon Shields]

Hi Anand,

On Fri, Sep 14, 2018 at 05:31:38PM +0530, Anand Moon wrote:
> Hi Simon,
> On Fri, 14 Sep 2018 at 08:00, Simon Shields <simon at lineageos.org> wrote:
> >
> > Hi Anand,
> >
> > On Thu, Sep 13, 2018 at 08:39:52PM +0530, Anand Moon wrote:
> > > Hi Simon,
> > >
> > > On Wed, 12 Sep 2018 at 17:25, Simon Shields <simon at lineageos.org> wrote:
> > > >
> > > > Hi,
> > > >
> > > > This patch series adds support for using U-Boot's SPL as the second
> > > > stage bootloader ("BL2") on Exynos4412 SoCs.
> > > >
> > > > - Patch #1 adds support for the EMMC/SD OM pin configuration, which is used
> > > >   by the boards I tested on.
> > > > - Patch #2 configures the magic values used to indicate system suspend
> > > >   state (which are identical to exynos5).
> > > > - Patch #3 renames the existing exynos4 clock/dmc initialisation code
> > > >   to reflect the fact that it only supports exynos4210.
> > > > - Patches #4 and #5 add/fill in structs reflecting the PMU and TZASC
> > > >   register layouts on exynos4412, respectively.
> > > > - Patch #6 adds the exynos4412 DMC and clock initialisation code and
> > > >   enables building the SPL on exynos4412 platforms.
> > > > - Patch #7 enables building the "mkexynosspl" utility for exynos4 SoCs.
> > > >
> > > > The majority of the logic in patch #6 comes from a vendor u-boot dump
> > > > (2010.12!), however, small portions (mostly code used for 2GB RAM
> > > > initialisation) were reverse engineered from the vendor
> > > > bootloader found on a GT-N7100.
> > > >
> > > > This patch series has been tested on a GT-I9300 (exynos4412, 1GB RAM)
> > > > and a GT-N7100 (exynos4412 prime, 2GB RAM), with a few additional
> > > > patchsets applied for board/HW support (which I intend to upstream in
> > > > the future).
> > > >
> > > > Cheers,
> > > > Simon
> > > >
> > >
> > > Could you elaborate more on how to generate stage bootloader (BL2) image,
> > > I am not aware of such process and what are next step to create SPL
> > > for Exynos platform.
> > >
> > > I have build these patches for Odroid-U3 boards, with no SPL enable.
> >
> > Of course!
> >
> > You need to add "select SUPPORT_SPL" to the relevant TARGET_ kconfig
> > entry (e.g. [0]). Then, you need to configure the SPL suitably in
> > include/configs/<target>.h - see [1], these values should not need
> > changing between boards. Finally, you need to enable some SPL
> > stuff in the defconfig (see [2]). That should allow u-boot to generate
> > a SPL binary, which should go in spl/<target>-spl.bin.
> >
> > After that, you need to assemble an image suitable for flashing to an
> > sdcard/eMMC. I use these two scripts [3], [4] combined with this BL1 [5]
> > (originally from the ODROID-X u-boot sources, which no longer appear
> > to be available) for eMMC and sdcard respectively.
> >
> > The usage of the script is:
> >
> > ./create_4412_<sd|emmc>_image.sh <bl1 binary> <spl binary> <u-boot.bin>
> >     <outfile>
> >
> > <outfile> can then be dd'd directly to an SD card or to the eMMC boot0
> > partition.
> >
> > Hope that gets things working for you!
> >
> > Cheers,
> > Simon
> >
> > >
> > > Best Regards
> > > -Anand
> >
> > [0]: https://github.com/fourkbomb/u-boot/blob/4be16a7/arch/arm/mach-exynos/Kconfig#L77
> > [1]: https://github.com/fourkbomb/u-boot/blob/4be16a7/include/configs/midas.h#L31-L53
> > [2]: https://github.com/fourkbomb/u-boot/blob/4be16a7/configs/midas_defconfig#L6-L10
> > [3]: https://github.com/fourkbomb/buildroot-external-midas/blob/master/board/midas/create_4412_emmc_image.sh
> > [4]: https://github.com/fourkbomb/buildroot-external-midas/blob/master/board/midas/create_4412_sd_image.sh
> > [5]: https://github.com/fourkbomb/buildroot-external-midas/blob/master/board/midas/p4412_s_fwbl1.bin
> 
> Thank you very much for this inside on building SPL image. I will give
> this a try on Odroid U3.
> 
> Do you have plan to add some low-level code to control clk memory cpu.
> 
> [0] https://github.com/SamsungARTIK/u-boot-artik/tree/artik-exynos/v2012.07/board/samsung/smdk4x12
> 
> Actually I failed to understand how the communication between the
> kernel binary and u-boot with out this code.

That code is not actually board-specific. It's added in patch #6.
All the BL2 does is initialise clocks and memory (DMC), then load U-Boot from the appropriate
boot medium.

> 
> Also what about trusted zone, and do we need to get this spl image
> signed by Samsung/Hardkernel to make this work.

As with other Exynos SoCs in U-Boot, this doesn't support loading
trustzone. As a result, you need to remove the "secure-firmware" node
from the Linux kernel (you can also do it with CONFIG_OF_BOARD_SETUP[0]).
Adding support for the TZSW could probably be done, but the goal here
was to remove blobs from the boot process - so I don't really have
any interest in adding TZSW support right now.

> 
> Best Regards
> -Anand

Cheers,
Simon

[0]: https://github.com/fourkbomb/u-boot/blob/4be16a7/board/samsung/midas/midas.c#L377-L402