[PATCH] board: samsung: add support for Samsung Exynos mobile device boards
Kaustabh Chakraborty
kauschluss at disroot.org
Sat Oct 18 20:04:35 CEST 2025
On 2025-10-17 20:19, Henrik Grimler wrote:
> Hi Kaustabh,
>
> Nice work on all of the linked patches!
>
> On Fri, Oct 17, 2025 at 10:07:35PM +0530, Kaustabh Chakraborty wrote:
>> Add support for a generic platform which intends to support multiple
>> boards powerid by Samsung Exynos SoCs. This patch also includes
>> initial
>> support for three boards:
>> * Samsung Galaxy A2 Core
>> * Samsung Galaxy J6
>> * Samsung Galaxy J7 Prime
>
> I think it would be easier to review this if you split the patch in two
> parts: first adding docs and common parts, and then the specific parts
> for exynos7870 and these devices.
>
>> Signed-off-by: Kaustabh Chakraborty <kauschluss at disroot.org>
>> ---
>> This patch has the following dependencies:
>> (NOTE: `x` indicates applied)
>>
>> armv8-broken-cntfrq -
>> https://patch.msgid.link/20251017-armv8-broken-cntfrq-v2-1-1e043cbb657e@disroot.org
>> clk-exynos7870 -
>> https://patch.msgid.link/20251017-clk-exynos7870-v1-0-83f90d425699@disroot.org
>> gpio-s5p-bank-fix -
>> https://patch.msgid.link/20251017-gpio-s5p-bank-fix-v1-1-41050462cea5@disroot.org
>> i2c-hs-exynos7 -
>> https://patch.msgid.link/20251017-i2c-hs-exynos7-v1-1-ca080895d4b6@disroot.org
>> mmc-dw-exynos7870 -
>> https://patch.msgid.link/20251017-mmc-dw-exynos7870-v1-0-a2c5139d9afe@disroot.org
>> phy-usb-exynos7870 -
>> https://patch.msgid.link/20251017-phy-usb-exynos7870-v1-0-5885b00f0c87@disroot.org
>> pinctrl-exynos7870 -
>> https://patch.msgid.link/20251017-pinctrl-exynos7870-v1-0-beaa92f95a0c@disroot.org
>> power-pmic-regulator-s2mpu05 -
>> https://patch.msgid.link/20251017-power-pmic-regulator-s2mpu05-v1-0-91cadc0f4156@disroot.org
>> serial-s5p-exynos8895 -
>> https://patch.msgid.link/20251017-serial-s5p-exynos8895-v1-1-b412dd112cfd@disroot.org
>> soc-pmu-exynos7 -
>> https://patch.msgid.link/20251017-soc-pmu-exynos7-v1-1-553d18eaab0d@disroot.org
>> usb-dwc3-exynos7870 -
>> https://patch.msgid.link/20251017-usb-dwc3-exynos7870-v1-0-fe46e2ed1908@disroot.org
>> ---
>> arch/arm/mach-exynos/Kconfig | 11 +-
>> board/samsung/exynos-mobile/Kconfig | 18 +
>> board/samsung/exynos-mobile/MAINTAINERS | 6 +
>> board/samsung/exynos-mobile/Makefile | 5 +
>> .../samsung/exynos-mobile/debug-exynos7870.config | 7 +
>> board/samsung/exynos-mobile/exynos-mobile.c | 372
>> +++++++++++++++++++++
>> board/samsung/exynos-mobile/exynos-mobile.env | 18 +
>> configs/exynos-mobile_defconfig | 71 ++++
>> doc/board/samsung/exynos-mobile.rst | 112 +++++++
>> doc/board/samsung/index.rst | 1 +
>> include/configs/exynos-mobile.h | 14 +
>> 11 files changed, 634 insertions(+), 1 deletion(-)
>
> [ skipping to docs for now ]
>
>> diff --git a/doc/board/samsung/exynos-mobile.rst
>> b/doc/board/samsung/exynos-mobile.rst
>> new file mode 100644
>> index
>> 0000000000000000000000000000000000000000..6390c66ffc38a41f01cb51c7406397cfc5a3d223
>> --- /dev/null
>> +++ b/doc/board/samsung/exynos-mobile.rst
>> @@ -0,0 +1,112 @@
>> +.. SPDX-License-Identifier: GPL-2.0+
>> +.. sectionauthor:: Kaustabh Chakraborty <kauschluss at disroot.org>
>> +
>> +Samsung Exynos Generic Boards (for mobile devices)
>> +==================================================
>> +
>> +Overview
>> +--------
>> +This document describes how to build and run U-Boot for Samsung
>> Exynos generic
>> +boards. Boards are expected to boot with a primary bootloader, such
>> as S-BOOT or
>> +S-LK, which hands off control to U-Boot, disguised as an Android boot
>> image.
>
> In my opinion exynos-mobile is a bit too generic. From the docs here
> it seems plan is to support devices that support android boot images
> with dt in Samsung's qcdt format. The oldest Exynos mobile device do
> not even support boot images though, and dt images has only been
> around since something like 2015. If I am not mistaken the newest
> devices also does not use dt images.
Well no, any Exynos would be supported by this variant, the only
factor is that U-Boot is used as a *secondary* boot loader. QCDT is
specific to the packaging of the u-boot binary (that too, is
located under a 7870-specific section), and if there are any other
packing methods, they can be documented here as well.
That being said, I've found 'exynos-mobile' to be most appropriate
(This is for mobile devices like phones and tablets, where we have
a proprietary primary boot loader). But if you have suggestions for
better names, let me know. :)
>
>> +U-Boot is packed with multiple FDTs since it targets multiple boards.
>> The
>> +appropriate FDT is selected during boot. Additionally, a DTB is also
>> required
>> +for embedding in the Android boot image. The previous bootloader can
>> apply
>> +useful overlays on it. Both DTBs are consulted for figuring out the
>> memory
>> +layout.
>
>> +Installation
>> +------------
>> +Building
>> +^^^^^^^^
>> +To buiid U-Boot, run the following commands
>
> Typo, buiid -> build
>
>> +.. prompt:: bash $
>> +
>> + make CROSS_COMPILE=aarch64-linux-gnu- O=.output
>> exynos-mobile_defconfig
>> + make CROSS_COMPILE=aarch64-linux-gnu- O=.output -j$(nproc)
>
> I think CROSS_COMPILE=aarch64-linux-gnu- can be dropped from the
> example, or are only
> aarch64 devices supported?
Plans were for aarch64. But if its possible to add armv7 support, then
that would be great! Is multiple arch-es for the same board possible?
>
>> +If succcessful, the U-Boot binary will be present in
>> ``.output/u-boot.bin``.
>
> Typo, succcessful -> successful.
>
>> +
>> +Preparation
>> +^^^^^^^^^^^
>> +The U-Boot binary is not flashable as-is, it needs to be encapsulated
>> in an
>> +Android boot image. Since it supports multiple boards, and devices
>> have
>> +different requirements (thanks to the lack of standards), this step
>> varies
>
> I think `(thanks to the lack of standards)` is a bit opinionated, and
> does not really add anything here, could you please remove it?
I agree. Will remove it.
>
>> +depending on your target.
>> +
>> +Exynos 7870 Boards
>> +""""""""""""""""""
>> +Create the following devicetree (named ``stub.dts``)
>> +
>> +.. code-block:: devicetree
>> +
>> + /dts-v1/;
>> +
>> + / {
>> + compatible = "samsung,exynos7870";
>> + #address-cells = <2>;
>> + #size-cells = <1>;
>> +
>> + model_info-chip = <7870>;
>> + model_info-hw_rev = <0>;
>> + model_info-hw_rev_end = <255>;
>> +
>> + chosen {
>> + };
>> +
>> + memory at 80000000 {
>> + device_type = "memory";
>> + reg = <0x0 0x80000000 0x0>;
>> + };
>> +
>> + memory at 100000000 {
>> + device_type = "memory";
>> + reg = <0x1 0x00000000 0x0>;
>> + };
>> + };
>> +
>> +The chosen node and memory ranges are populated by S-BOOT.
>> +
>> +Compile it to a devicetree blob, then use ``dtbTool-exynos`` in order
>> to pack it
>> +in the QCDT format [1]_, using the following commands:
>> +
>> +.. prompt:: bash $
>> +
>> + dtc -I dts -O dtb -o stub.dtb stub.dts
>> + dtbTool-exynos -o stub.dt.img stub.dtb
>> +
>> +Finally, use mkbootimg by osm0sis [2]_ to generate the boot image:
>> +
>> +.. prompt:: bash $
>> +
>> + mkbootimg -o u-boot.img \
>> + --kernel .output/u-boot.bin \
>> + --dt stub.dt.img
>> +
>> +Offsets are not provided to ``mkbootimg`` as S-BOOT ignores them.
>> +
>> +Flashing
>> +^^^^^^^^
>> +If flashing for the first time, it must be done via Samsung's
>> Download (Odin)
>> +mode. Heimdall can be used for flashing, like so:
>
> Maybe it would be useful to link to Heimdall in references as well.
>
> Best regards,
> Henrik Grimler
>
>> +.. prompt:: bash $
>> +
>> + heimdall flash --BOOT u-boot.img
>> +
>> +However, if U-Boot is already installed, you may also use its
>> fastboot interface
>> +for flashing. Boot into the boot menu by holding the volume down key.
>> Enable
>> +fastboot mode from there, connect the device to your host, then run:
>> +
>> +.. prompt:: bash $
>> +
>> + fastboot flash boot u-boot.img
>> +
>> +To flash an OS image in internal storage, fastboot is a reliable
>> option.
>> +
>> +References
>> +----------
>> +.. [1] https://wiki.postmarketos.org/wiki/QCDT
>> +.. [2] https://github.com/osm0sis/mkbootimg
>> diff --git a/doc/board/samsung/index.rst b/doc/board/samsung/index.rst
>> index
>> 1b92c9518a57df102c2b64ff934b460548ce3d53..1fbe88130c049e1a33d22ae9230fb60ddccea131
>> 100644
>> --- a/doc/board/samsung/index.rst
>> +++ b/doc/board/samsung/index.rst
>> @@ -8,4 +8,5 @@ Samsung
>>
>> axy17lte
>> e850-96
>> + exynos-mobile
>> n1
>> diff --git a/include/configs/exynos-mobile.h
>> b/include/configs/exynos-mobile.h
>> new file mode 100644
>> index
>> 0000000000000000000000000000000000000000..862db5779ef4c9ff7f53bef78d7cee5107b7226e
>> --- /dev/null
>> +++ b/include/configs/exynos-mobile.h
>> @@ -0,0 +1,14 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * Samsung Exynos Generic Board Configuration (for mobile devices)
>> + *
>> + * Copyright (C) 2025 Kaustabh Chakraborty <kauschluss at disroot.org>
>> + */
>> +
>> +#ifndef __CONFIG_EXYNOS_MOBILE_H
>> +#define __CONFIG_EXYNOS_MOBILE_H
>> +
>> +#define CPU_RELEASE_ADDR secondary_boot_addr
>> +#define CFG_SYS_BAUDRATE_TABLE {9600, 115200}
>> +
>> +#endif /* __CONFIG_EXYNOS_MOBILE_H */
>>
>> ---
>> base-commit: 582a04763aa80738c1c8ac60c47d1a5159a42833
>> change-id: 20251017-board-exynos-mobile-7c7d43832693
>>
>> Best regards,
>> --
>> Kaustabh Chakraborty <kauschluss at disroot.org>
>>
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