diff --git a/.gitattributes b/.gitattributes index 7a7c4163560..735b13da278 100644 --- a/.gitattributes +++ b/.gitattributes @@ -6,3 +6,4 @@ *.ttf binary *.gz binary *.png binary +*.svg binary diff --git a/common/board_f.c b/common/board_f.c index baf98fb8ec8..c4561874496 100644 --- a/common/board_f.c +++ b/common/board_f.c @@ -254,7 +254,7 @@ static int show_dram_config(void) print_size(gd->ram_size, ""); if (!sizes_near(gd->ram_size, size)) { - printf(" (effective "); + printf(" (total "); print_size(size, ")"); } board_add_ram_info(0); diff --git a/doc/develop/memory.rst b/doc/develop/memory.rst index e9e65ba4c6c..5177229630d 100644 --- a/doc/develop/memory.rst +++ b/doc/develop/memory.rst @@ -1,7 +1,7 @@ .. SPDX-License-Identifier: GPL-2.0-or-later Memory Management ------------------ +================= .. note:: @@ -47,3 +47,159 @@ this:: ... eventually: LCD or video framebuffer ... eventually: pRAM (Protected RAM - unchanged by reset) 0x00ff ffff [End of RAM] + +System RAM Utilization in U-Boot in ARM +--------------------------------------- + +Let us break down the relevant parts of the execution sequence where system RAM +comes into play. Please note that these are individual pieces of the entire +boot sequence. It is not exhaustive, rather it aims to show only the pieces +where the system RAM is modified. See arch/arm/lib/crt0* to understand the +complete execution sequence. + +Also note that the below sequence is not a hard and fast rule on how DRAM usage +would be and an architecture and board specific analysis is required for the +exact flow. + +SPL Flow +........ + + #. Pre-DRAM + + Prior to setting up of the DRAM, the stack, malloc is defined as below + possibly sitting on a smaller readily available memory (SRAM etc.): + + .. image:: pics/spl_before_reloc.svg + :alt: contents of ready RAM before relocation in SPL + + Please see CONFIG_SPL_EARLY_BSS if BSS initialization is needed prior + to entering board_init_f(). + + + #. DRAM Initialization + + This is typically triggered by board_init_f prior to relocating the stack + and the GD (optionally) to the system RAM. DRAM drivers reside in + drivers/ram/. Their probe/configuration can be done either via placing the + logic in dram_init() or wherever deemed applicable within board_init_f. + + Post board_init_f, spl_relocate_stack_gd() is called to relocate the stack + and the GD to the newly initialized DRAM. If CONFIG_SPL_SYS_MALLOC_SIMPLE + is set it is also possible to use some amount of this DRAM stack as memory + pool for malloc_simple. + + Both of which are an optional move at this point in the sequence. This is + still an intermediate environment. + + #. Final Environment Set Up + + The final environment is setup and the system RAM now looks like this: + + .. image:: pics/spl_after_reloc.svg + :alt: contents of DRAM after relocation in SPL + + Again stack and gd are an optional move and may still remain in the + available RAM (SRAM, locked cache etc.) + +U-Boot Proper Flow +.................. + + TODO: this section is still under progress + + #. DRAM Initialization + + This follows the same as in SPL flow. In board_init_f(), a part of memory + is reserved at the end of RAM (see reserve_* functions in init_sequence_f) + + #. Code Relocation + + relocate_code() is called which relocates U-Boot code from the current + location into the relocation destination in system RAM. Typically it is + relocated to the upper portion of the memory. So DRAM now has: + * stack + * gd + * code + + The code relocation happens to the upper portion of the memory after certain + portion of memory is reserved. This is memory that is intended to not be + "touched" by U-Boot. + + #. Final Environment Set Up + + At this stage we are completely running out of the system RAM with: + * stack + * gd + * code + * bss + * initialized non-const data + * initialized const data + + It is better to do a complete analysis to visualize the layers the system + RAM is composed of at the end of this flow. This is entirely dependent on + CPU/SoC architecture. + +Getting information about system RAM +.................................... + + At boot: + + The prints given by announce_dram_init() and show_dram_config() come up in the + boot banner like so:: + + DRAM: 2 GiB (total 32 GiB) + + U-Boot supports addressing upto 39-bit. To avoid trying to access higher + addresses in systems with > 39-bit addresses, U-Boot caps itself (gd->ram_size) + to the first bank. This is also inline with philosophy that U-Boot is a + bootloader and not a full-fledged operating system. The first value represents + this memory that is available for U-Boot while the "total" value represents the + total system RAM available on the device. + + Getting the most basic information on how system RAM has been set up is by + running `bdinfo` at U-Boot prompt:: + + => bdinfo + boot_params = 0x0000000000000000 + DRAM bank = 0x0000000000000000 + -> start = 0x0000000080000000 + -> size = 0x0000000080000000 + DRAM bank = 0x0000000000000001 + -> start = 0x0000000880000000 + -> size = 0x0000000780000000 + flashstart = 0x0000000000000000 + flashsize = 0x0000000000000000 + flashoffset = 0x0000000000000000 + baudrate = 115200 bps + relocaddr = 0x00000000ffec1000 + reloc off = 0x000000007f6c1000 + Build = 64-bit + current eth = ethernet@46000000port@1 + ethaddr = 3c:e0:64:62:4b:4e + IP addr = + fdt_blob = 0x00000000fde7df60 + lmb_dump_all: + memory.count = 0x1 + memory[0] [0x80000000-0xffffffff], 0x80000000 bytes flags: none + reserved.count = 0x2 + reserved[0] [0x9e800000-0xabffffff], 0x0d800000 bytes flags: no-map + reserved[1] [0xfce79f50-0xffffffff], 0x031860b0 bytes flags: no-overwrite + devicetree = separate + serial addr = 0x0000000002880000 + width = 0x0000000000000000 + shift = 0x0000000000000002 + offset = 0x0000000000000000 + clock = 0x0000000002dc6c00 + arch_number = 0x0000000000000000 + TLB addr = 0x00000000ffff0000 + irq_sp = 0x00000000fde7df50 + sp start = 0x00000000fde7df50 + Early malloc usage: 3288 / 8000 + + + Here you are able to see the banks of DDR that have been set up in DRAM bank + -> start and -> size as well as the reserved memories in lmb_dump_all. + +Testing Memory +-------------- + + Please see doc/README.memory-test diff --git a/doc/develop/pics/spl_after_reloc.svg b/doc/develop/pics/spl_after_reloc.svg new file mode 100644 index 00000000000..93e3d599526 --- /dev/null +++ b/doc/develop/pics/spl_after_reloc.svg @@ -0,0 +1,4 @@ + + + +
Heap (simple_malloc)
Global Data
Stack
0x0
CONFIG_SPL_STACK_R_MALLOC_SIMPLE_LEN
gd->malloc_base
gd, gd->start_addr_sp
CONFIG_SPL_STACK_R_ADDR
DRAM SPL after relocation
SPL BSS
CONFIG_SPL_BSS_MAX_SIZE
CONFIG_SPL_BSS_START_ADDR
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