Move this section of the README into doc/ with some minor updates to mention SPL and user lower-case hex.
Signed-off-by: Simon Glass sjg@chromium.org ---
Changes in v2: - Mention that these docs need updating
README | 45 ---------------------------------------- doc/develop/index.rst | 1 + doc/develop/memory.rst | 47 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 48 insertions(+), 45 deletions(-) create mode 100644 doc/develop/memory.rst
diff --git a/README b/README index 4be1e8c22a0..d73042406b6 100644 --- a/README +++ b/README @@ -2516,51 +2516,6 @@ On RISC-V, the following registers are used:
==> U-Boot will use gp to hold a pointer to the global data
-Memory Management: ------------------- - -U-Boot runs in system state and uses physical addresses, i.e. the -MMU is not used either for address mapping nor for memory protection. - -The available memory is mapped to fixed addresses using the memory -controller. In this process, a contiguous block is formed for each -memory type (Flash, SDRAM, SRAM), even when it consists of several -physical memory banks. - -U-Boot is installed in the first 128 kB of the first Flash bank (on -TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After -booting and sizing and initializing DRAM, the code relocates itself -to the upper end of DRAM. Immediately below the U-Boot code some -memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN -configuration setting]. Below that, a structure with global Board -Info data is placed, followed by the stack (growing downward). - -Additionally, some exception handler code is copied to the low 8 kB -of DRAM (0x00000000 ... 0x00001FFF). - -So a typical memory configuration with 16 MB of DRAM could look like -this: - - 0x0000 0000 Exception Vector code - : - 0x0000 1FFF - 0x0000 2000 Free for Application Use - : - : - - : - : - 0x00FB FF20 Monitor Stack (Growing downward) - 0x00FB FFAC Board Info Data and permanent copy of global data - 0x00FC 0000 Malloc Arena - : - 0x00FD FFFF - 0x00FE 0000 RAM Copy of Monitor Code - ... eventually: LCD or video framebuffer - ... eventually: pRAM (Protected RAM - unchanged by reset) - 0x00FF FFFF [End of RAM] - - System Initialization: ----------------------
diff --git a/doc/develop/index.rst b/doc/develop/index.rst index 0d0e60ab56c..cbea38d4323 100644 --- a/doc/develop/index.rst +++ b/doc/develop/index.rst @@ -13,6 +13,7 @@ General codingstyle designprinciples docstyle + memory patman process release_cycle diff --git a/doc/develop/memory.rst b/doc/develop/memory.rst new file mode 100644 index 00000000000..816fe3ec5db --- /dev/null +++ b/doc/develop/memory.rst @@ -0,0 +1,47 @@ +.. SPDX-License-Identifier: GPL-2.0+: + +Memory Management +----------------- + +Note: This information is outdated and needs to be updated. + +U-Boot runs in system state and uses physical addresses, i.e. the +MMU is not used either for address mapping nor for memory protection. + +The available memory is mapped to fixed addresses using the +memory-controller. In this process, a contiguous block is formed for each +memory type (Flash, SDRAM, SRAM), even when it consists of several +physical-memory banks. + +U-Boot is installed in XIP flash memory, or may be loaded into a lower region of +RAM by a secondary program loader (SPL). After +booting and sizing and initialising DRAM, the code relocates itself +to the upper end of DRAM. Immediately below the U-Boot code some +memory is reserved for use by malloc() [see CONFIG_SYS_MALLOC_LEN +configuration setting]. Below that, a structure with global Board-Info +data is placed, followed by the stack (growing downward). + +Additionally, some exception handler code may be copied to the low 8 kB +of DRAM (0x00000000 ... 0x00001fff). + +So a typical memory configuration with 16 MB of DRAM could look like +this:: + + 0x0000 0000 Exception Vector code + : + 0x0000 1fff + 0x0000 2000 Free for Application Use + : + : + + : + : + 0x00fb ff20 Monitor Stack (Growing downward) + 0x00fb ffac Board Info Data and permanent copy of global data + 0x00fc 0000 Malloc Arena + : + 0x00fd ffff + 0x00fe 0000 RAM Copy of Monitor Code + ... eventually: LCD or video framebuffer + ... eventually: pRAM (Protected RAM - unchanged by reset) + 0x00ff ffff [End of RAM]