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
  1. 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
  1. 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
  1. 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