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linux/Documentation/arch/arm/samsung/bootloader-interface.rst
Jonathan Corbet e790a4ce52 arm: docs: Move Arm documentation to Documentation/arch/
Architecture-specific documentation is being moved into Documentation/arch/
as a way of cleaning up the top-level documentation directory and making
the docs hierarchy more closely match the source hierarchy.  Move
Documentation/arm into arch/ (along with the Chinese equvalent
translations).

Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Jernej Skrabec <jernej.skrabec@gmail.com>
Cc: Samuel Holland <samuel@sholland.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Alim Akhtar <alim.akhtar@samsung.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: linux-doc@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-arch@vger.kernel.org
Acked-by: Alexandre TORGUE <alexandre.torgue@foss.st.com>
Reviewed-by: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2023-06-12 06:33:40 -06:00

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==========================================================
Interface between kernel and boot loaders on Exynos boards
==========================================================
Author: Krzysztof Kozlowski
Date : 6 June 2015
The document tries to describe currently used interface between Linux kernel
and boot loaders on Samsung Exynos based boards. This is not a definition
of interface but rather a description of existing state, a reference
for information purpose only.
In the document "boot loader" means any of following: U-boot, proprietary
SBOOT or any other firmware for ARMv7 and ARMv8 initializing the board before
executing kernel.
1. Non-Secure mode
Address: sysram_ns_base_addr
============= ============================================ ==================
Offset Value Purpose
============= ============================================ ==================
0x08 exynos_cpu_resume_ns, mcpm_entry_point System suspend
0x0c 0x00000bad (Magic cookie) System suspend
0x1c exynos4_secondary_startup Secondary CPU boot
0x1c + 4*cpu exynos4_secondary_startup (Exynos4412) Secondary CPU boot
0x20 0xfcba0d10 (Magic cookie) AFTR
0x24 exynos_cpu_resume_ns AFTR
0x28 + 4*cpu 0x8 (Magic cookie, Exynos3250) AFTR
0x28 0x0 or last value during resume (Exynos542x) System suspend
============= ============================================ ==================
2. Secure mode
Address: sysram_base_addr
============= ============================================ ==================
Offset Value Purpose
============= ============================================ ==================
0x00 exynos4_secondary_startup Secondary CPU boot
0x04 exynos4_secondary_startup (Exynos542x) Secondary CPU boot
4*cpu exynos4_secondary_startup (Exynos4412) Secondary CPU boot
0x20 exynos_cpu_resume (Exynos4210 r1.0) AFTR
0x24 0xfcba0d10 (Magic cookie, Exynos4210 r1.0) AFTR
============= ============================================ ==================
Address: pmu_base_addr
============= ============================================ ==================
Offset Value Purpose
============= ============================================ ==================
0x0800 exynos_cpu_resume AFTR, suspend
0x0800 mcpm_entry_point (Exynos542x with MCPM) AFTR, suspend
0x0804 0xfcba0d10 (Magic cookie) AFTR
0x0804 0x00000bad (Magic cookie) System suspend
0x0814 exynos4_secondary_startup (Exynos4210 r1.1) Secondary CPU boot
0x0818 0xfcba0d10 (Magic cookie, Exynos4210 r1.1) AFTR
0x081C exynos_cpu_resume (Exynos4210 r1.1) AFTR
============= ============================================ ==================
3. Other (regardless of secure/non-secure mode)
Address: pmu_base_addr
============= =============================== ===============================
Offset Value Purpose
============= =============================== ===============================
0x0908 Non-zero Secondary CPU boot up indicator
on Exynos3250 and Exynos542x
============= =============================== ===============================
4. Glossary
AFTR - ARM Off Top Running, a low power mode, Cortex cores and many other
modules are power gated, except the TOP modules
MCPM - Multi-Cluster Power Management