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Commit a28ab162 authored by Krzysztof Kozlowski's avatar Krzysztof Kozlowski Committed by Jonathan Corbet
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Documentation: ARM: EXYNOS: Describe boot loaders interface 



Various boot loaders for Exynos based boards use certain memory
addresses during booting for different purposes. Mostly this is one of
following :
1. as a CPU boot address,
2. for storing magic cookie related to low power mode (AFTR, sleep).

The document, based solely on kernel source code, tries to group the
information scattered over different files. This would help in the
future when adding support for new SoC or when extending features
related to low power modes.

Signed-off-by: default avatarKrzysztof Kozlowski <k.kozlowski.k@gmail.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent b322582f

Documentation/arm/Samsung/Bootloader-interface.txt

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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                         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





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

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 (only Exynos3250)      Secondary CPU boot up indicator