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